Patent Publication Number: US-2021186320-A1

Title: Optical measurement systems and processes with non-telecentric projection of fixation target to eye

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/951,405, filed Dec. 20, 2019, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of this invention pertain to optical measurement equipment, and more particularly, to optical measurement systems and processes which include fixation targets for causing a subject&#39;s eye to accommodate during measurement. 
     BACKGROUND 
     Autorefractors and aberrometers (e.g., wavefront aberrometers) measure the refraction of a subject&#39;s eye using infrared light. It is desirable that the eye relax accommodation while the refraction is being measured to avoid an unknown change in the eye&#39;s focal power during the measurement which can lead to errors or inaccuracy in the measured refraction. Accordingly, autorefractors and aberrometers typically employ a fixation target for a person to view while the refractive state of the eye is being measured. One purpose of the fixation target is to draw the focus of the eye to its most distant refractive state, and then beyond, to so-call “fog” the eye while the refraction is being measured. Under these conditions, the eye attempts to keep the target in focus by relaxing accommodation, which as noted above is desirable. A patient&#39;s most distant refraction is also used for planning refractive eye surgeries. 
     However, with conventional autorefractors and aberrometers, about ten percent of people do not fully relax accommodation in response to the presented target. Because autorefractors are not completely reliable in fully relaxing the accommodation of a significant percentage of patients&#39; eyes, the resulting refraction measurements are often erroneous or inaccurate. Furthermore, because it is not known whether this issue has occurred or not with a particular patient, there is a lack of confidence or trust in the results for all patients. Experiments where eye glasses have been prescribed based on autorefractions alone have resulted in a high fraction of unhappy patients. This leads optometrists to prescribe eye glasses based on manifest refractions measured with a phoropter instead of using results produced by an autorefractor or aberrometer. 
     Accordingly, it would be desirable to provide a fixation target system which is more effective in drawing out the eye&#39;s refractive state and stimulating fully relaxed accommodation for a greater percentage of patients during refraction measurements with an autorefractor or aberrometer. It would also be desirable to provide an optical measurement instrument, such as an autorefractor or aberrometer, which includes such a fixation target system. It would be further desirable to provide an improved method of drawing out the eye&#39;s refractive state to produce fully relaxed accommodation for a greater percentage of patients. 
     SUMMARY OF THE INVENTION 
     In one aspect, a system comprises: a wavefront aberrometer configured to measure a refraction of an eye; at least one processor; a first movable stage, wherein the first movable stage is movable with respect to the eye under control of the at least one processor; a second movable stage mounted on the first movable stage, wherein the second movable stage is independently movable with respect to the first movable stage and with respect to the eye, under control of the at least one processor; a fixation target for presentation by the system to the eye to cause the eye to accommodate during a process of measuring the refraction of the eye, wherein the fixation target is disposed on the second movable stage; and an optical system disposed in an optical path between the fixation target and the eye, wherein the optical system is configured for non-telecentric projection of the fixation target upon the eye. 
     In some embodiments, the optical system comprises at least a first lens which is not disposed on the first stage or second stage. 
     In some embodiments, the optical system comprises at least a second lens which is disposed on the second stage. 
     In some embodiments, the optical system comprises: a second lens disposed on the first stage and not disposed on the second stage; and a third lens disposed on the second stage, wherein a distance between the second lens and the third lens is less than a focal length of the second lens. 
     In some embodiments, the first and second lenses comprise two achromatic doublets, with more curved sides of the lenses facing each other. 
     In some embodiments, the aberrometer comprises: a light source; a Shack-Hartmann wavefront sensor; and a pair of lenses arranged as a telescope and configured to deliver a probe beam to the eye and returning light from the eye to the Shack-Hartmann wavefront sensor for measuring the refraction of the eye, wherein the Shack-Hartmann wavefront sensor and a first one of the pair of lenses is disposed on the first stage, and wherein a second one of the pair of lenses is not disposed on the first stage or the second stage. 
     In some embodiments, the fixation target comprises a circular pattern with a pair of cross hairs crossing at a middle of the circular pattern. 
     In another aspect, a method comprises: providing an arrangement comprising: a first movable stage, wherein the first movable stage is movable under control of the at least one processor with respect to an eye of a subject, a second movable stage disposed on the first movable stage, wherein the second movable stage is independently movable with respect to the first movable stage and with respect to the eye, under control of the at least one processor, a fixation target disposed on the second movable stage, and an optical system disposed in an optical path between the fixation target and the eye, wherein the optical system projects the fixation target upon the eye; the at least one processor moving the first movable stage with respect to the eye to a first stage position where the fixation target draws a focus of the eye to near its far point; stopping movement of the first movable stage with respect to the eye at the first stage position; and while the first movable stage is stopped, moving the second movable stage with respect to the first movable stage and the eye to a second stage position where the fixation target is moved away from the eye by an additional amount such that blur cues of the fixation target indicate to the subject that the fixation target is moving away from the eye at a same time that a size of an image of the fixation target on a retina of the eye decreases. 
     In some embodiments, the optical system non-telecentrically projects the fixation target upon the eye. 
     In some embodiments, the method further comprises measuring a refraction of the eye with the first movable stage at the first stage position and the second stage at the second stage position. 
     In some embodiments, measuring the refraction of the eye with a wavefront aberrometer having a wavefront sensor and a telescope, wherein a first lens of the telescope is disposed on the first stage and a second lens of the telescope is not disposed on the first stage or the second stage. 
     In some embodiments, the fixation target comprises a circular pattern with a pair of cross hairs crossing at a middle of the circular pattern. 
     In some embodiments, the optical system comprises at least a first lens which is not disposed on the first stage or second stage, a second lens disposed on the first stage and not disposed on the second stage, and a third lens disposed on the second stage, wherein a distance between the second lens and the third lens is less than a focal length of the second lens, and wherein moving the second stage comprises moving the third lens and the fixation target with respect to the second lens. 
     In some embodiments, the fixation target is provided via a video display, and wherein the method comprises electronically making a size of the fixation target on the video display smaller while moving the second movable stage to the second stage position. 
     In yet another aspect a system comprises: a first movable stage, wherein the first movable stage is movable under control of the at least one processor with respect to an eye of a subject; a second movable stage mounted on the first movable stage, wherein the second movable stage is independently movable with respect to the first movable stage and with respect to the eye, under control of the at least one processor; a fixation target which is disposed on the second movable stage; and an optical system disposed in an optical path between the fixation target and the eye, wherein the optical system is configured for projecting the fixation target upon the eye to accommodate the eye, and wherein moving the second movable stage with respect to the first movable stage and the eye to a position where the fixation target is moved away from the eye by an additional amount causes blur cues of the fixation target to indicate to the subject that the fixation target is moving away from the eye at a same time that a size of an image of the fixation target on a retina of the eye decreases. 
     In some embodiments, the optical system non-telecentrically projects the fixation target upon the eye. 
     In some embodiments, the optical system comprises at least a first lens which is not disposed on the first stage or second stage. 
     In some embodiments, the optical system comprises at least a second lens which is disposed on the second stage. 
     In some embodiments, the optical system comprises: a second lens disposed on the first stage and not disposed on the second stage; and a third lens disposed on the second stage, wherein a distance between the second lens and the third lens is less than a focal length of the second lens. 
     In some embodiments, the system further comprises a video display, wherein the fixation target is provided via the video display, and wherein the at least one processor is configured to electronically make a size of the fixation target on the video display smaller while moving the second movable stage to the second stage position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages will be facilitated by referring to the following detailed description that sets forth illustrative embodiments using principles of the invention, as well as to the accompanying drawings, in which like numerals refer to like parts throughout the different views. Like parts, however, do not always have like reference numerals. Further, the drawings are not drawn to scale, and emphasis has instead been placed on illustrating the principles of the invention. All illustrations are intended to convey concepts, where relative sizes, shapes, and other detailed attributes may be illustrated schematically rather than depicted literally or precisely. 
         FIG. 1  illustrates an example embodiment of an optical measurement system which includes a wavefront aberrometer. 
         FIG. 2  illustrates an example of a fixation target system. 
         FIG. 3  illustrates another example of a fixation target system. 
         FIGS. 4A and 4B  illustrate paths of light rays propagating to the retina of an eye from a target presented by fixation target systems of  FIGS. 2 and 3  when the target is in a first location with respect to the eye, and then moved further away from the eye. 
         FIGS. 5A and 5B  illustrate images on the retina of the eye produced by a target of the fixation target systems of  FIGS. 2 and 3  when the target is in a first location with respect to the eye, and then moved further away from the eye. 
         FIG. 6  illustrates yet another example of a fixation target system. 
         FIGS. 7A and 7B  illustrate images on the retina of the eye produced by a target of the fixation target system of  FIG. 6  when the target is in a first location with respect to the eye, and then moved further away from the eye. 
         FIG. 8  is a flowchart of an example embodiment of a method of measuring one or more characteristics of an eye with a wavefront aberromoter. 
         FIG. 9A  illustrates a front perspective view showing an optical measurement system according to many embodiments. 
         FIG. 9B  illustrates a rear perspective view showing an optical measurement system according to many embodiments. 
         FIG. 9C  illustrates a side perspective view showing an optical measurement system according to many embodiments. 
         FIG. 10  is a block diagram of a system including an optical measurement instrument, and a position of an eye relative to the system according to one or more embodiments described herein which may be used by the optical measurement. 
         FIGS. 11A and 11B  illustrate together an assembly illustrating a suitable configuration and integration of an optical coherence tomographer subsystem, a wavefront aberrometer subsystem a corneal topographer subsystem, an iris imaging subsystem, a fixation target subsystem according to a non-limiting embodiment of the present invention. 
         FIG. 12  is a block diagram of an OCT assembly according to many embodiments of the present invention. 
         FIG. 13  is a schematic drawing of a human eye. 
         FIG. 14A  illustrates a preferred scanning region for the OCT subsystem according to many embodiments of the present invention. 
         FIG. 14B  shows a representative graph of an intensity of an OCT signal of an OCT subsystem according to many embodiments as a function of depth along the axis defining the axial length of the eye. 
         FIG. 14C  shows a cross-section of an eye obtained by an optical measurement system of the present invention using an OCT subsystem according to the present invention 
         FIG. 15  is a 3-dimensional representation of an anterior portion of an eye obtained using the optical measurement system according to many embodiments. 
         FIG. 16  is a flowchart of an example embodiment of a method for measuring one or more characteristics of an eye, including wavefront aberrometry, corneal topography and OCT measurements at various locations with the eye along the axial length of the eye. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of optical measurement systems and methods for measuring aberrations of an eye to illustrate various aspects and advantages of these devices and methods are described below. However, it should be understood that the principles involved in these devices and methods can be employed in a variety of other contexts, and therefore the novel devices and method disclosed and claimed here should not be construed as being limited to the example embodiments described below. 
     U.S. Pat. No. 6,550,917, which is incorporated herein by reference, describes an instrument which includes a wavefront aberrometer, in particular a Shack-Hartmann wavefront aberrometer that provides an adjustable telescope in the forward path from the light source to the eye and in the return path from the eye to the wavefront sensor. The adjustable telescope employs a moving stage to move one lens of the telescope with respect to the other, and a feedback arrangement whereby data from the wavefront sensor is employed to control a motor for the moving stage to move the stage to the desired location where the wavefront sensor sees collimated return light from the eye. The moving stage may be a common linear travel stage with stepper (or servo) motor drives and a position encoder. The position of the moving stage may be calibrated so the stage position corresponds to the refractive power of the eye being measured. 
       FIG. 1  illustrates an embodiment of a measurement instrument employing a wavefront sensor. In particular,  FIG. 1  illustrates a wavefront aberrometer  1000  for making wavefront measurements of a subject&#39;s eye  101 . Among other components, wavefront aberrometer  1000  includes a probe beam light source  1010 , a wavefront sensor  1020 , and other components on a movable stage  1030 , at least one processor  1040 , memory  1050  associated with the at least one processor  1040 , and an iris camera  1060 . 
     Probe light beam source  1010  may comprise a laser, a laser diode, LED, or a super-luminescent diode (SLD), which may be connected to an optical fiber. For safety reasons, probe beam light source  1010  may be a pulsed light source, may be limited to a small power level, and may be outside the normal visual detection range, e.g. infrared. 
     Wavefront sensor  1020  is a Shack-Hartmann wavefront sensor. In other embodiments, a shearing interferometer or a Moiré deflectometer may be employed as a wavefront sensor. Wavefront sensor  1020  includes a lenslet array  1022  and a detector array (also known as a “pixel array”)  1024 . Wavefront data from detector array  1024  is supplied to processor  1040  and associated memory  1050  to execute one or more algorithms to determine a wavefront of a light beam received from the eye  101 . Beneficially, processor  1040  may perform these algorithms in accordance with instructions stored in memory  1050 . The operation of a Shack-Hartmann wavefront sensor in a wavefront aberrometer such as wavefront aberrometer  1000  may be understood with reference to U.S. Pat. No. 6,550,917, which is incorporated by reference, and will not be repeated here. 
     Wavefront aberrometer  1000  includes an optical imaging system comprising a telescope having a pair of lenses  1163  and  1164 , and a dynamic range limiting aperture  1165 , for example in an optical screening structure. 
     Processor  1040  controls the operation of wavefront aberrometer  1000  and can receive image data from wavefront sensor  1020  to measure the refraction of eye  101 , including high order aberrations. Processor  1040  may also control movement of movable stage  1030 , as described in more detail below. Processor  1040  may include any suitable components, such as one or more microprocessors, one or more field-programmable gate array (FPGA), and one or more memory storage devices. 
     Beneficially, wavefront sensor  1020  operates in conjunction with processor  1040  and associated memory  1050  to perform wavefront measurements on eye  101  to measure, inter alia, a refraction of eye  101 . 
     As explained above, it is desirable that eye  101  relax accommodation while the refraction is being measured to avoid an unknown change in the focal power of eye  101  during the measurement which can lead to errors in the measured refraction. Accordingly, wavefront aberrometer  1000  includes a fixation target  1082  which includes a fixation target  1082  for a person to view while the refractive state of eye  101  is being measured to draw the focus of eye  101  to its most distant refractive state, and then beyond, to fog eye  101  while the refraction is being measured. 
       FIG. 2  illustrates an example of a fixation target system  2000 . Fixation target system  2000  includes fixation target  1082 , a first lens  1083 , a second lens  1084 , and a third lens  1085 . Fixation target system  2000  includes a movable stage  1088  on which second lens  1084 , third lens  1085  and fixation target  1082  are disposed or mounted. First lens  1083  is not disposed or mounted on movable stage  1088 . In fixation target system  2000 , eye  101  is located one focal length from first lens  1083 . 
     In fixation target system  2000 , the distance between second lens  1084  and third lens  1085  is f 2 +f 3 , where f 2  is the focal length of second lens  1084  and f 3  is the focal length of third lens  1085 . This is sometimes referred to as a Badal arrangement. In this arrangement, light rays that reach eye  101  are telecentric when they leave target  1082 . By definition that means the chief ray is parallel to the optical axis at target  1082 . The chief ray is defined as the ray that leaves the edge of target  1082  and ultimately passes through the center of the stop of the system, which is the pupil of eye  101 . 
     Movable stage  1088  may be referred to as a Badal stage, and in some embodiments may comprise the movable stage  1030  of wavefront aberrometer  1000  of  FIG. 1 . In particular, it is commonly noted that in a Badal arrangement, target  1082  appears to maintain constant size to a viewer as it moves away from eye  101  toward optical infinity. A key advantage of the arrangement is that a simple optical system can provide a similar visual appearance to a wide range of patients, from strong myopes of −20 Diopters through hyperopes up to +20 Diopters. 
     During an a refraction measurement, the at least one processor  1040  moves movable stage  1088  and thereby moves target  1082  away from first lens  1083  to make target  1082  appear farther away from eye  101 . Eye  101  attempts to keep target  1082  in focus by relaxing accommodation. In such a system the only cue that the patient or subject receives from eye  101  that target  1082  is moving more distant from eye  101  is that the image of target  1082  on the retina of eye  101  becomes blurred. 
     However, an underlying problem in the fixation target system  2000  is that it creates a visual experience that contains conflicting cues to a viewer. The brain knows that when something moves farther away, the apparent size of it should become smaller. So the constant size of the image of target  1082  on the retina of eye  101  which is projected by the Badal arrangement of fixation target system  2000  creates conflicting visuals cue to eye  101 . In the presence of these conflicting visual cues, some people&#39;s eyes will not relax accommodation completely. 
     However, the situation is actually a bit worse. Fogging or blurring target  1082  actually increases the apparent size of the image of target  1082  on the retina of eye  101  by a small amount. The effect is particularly pronounced for simple geometric targets, like white circular patterns on a black background. If we consider the target size appearance to be defined by the illuminated region on the retina, a Badal arrangement such as in fixation target system  2000  only maintains a constant target size for an eye with an infinitely small pupil. 
       FIG. 3  illustrates another example of a fixation target system  3000 . Fixation target system  3000  is similar to fixation target system  2000  with the exception that fixation target system  3000  includes a second movable stage  1089  on which target  1082  is disposed or mounted, wherein the second movable stage  1089  is disposed or mounted on first movable stage  1088 . The at least one processor  1040  may independently move second movable stage  1089  with respect to first movable stage  1088  and eye  101 . Second movable stage  1089  may be referred to as a fogging stage as its purpose is to move target  1082  further away from eye  101  once movable stage  1088  has placed target  1082  near the far focus point of eye  101 , so as to fog eye  101 . 
     First movable stage  1088  has a large range and is used to position target  1082  in the range for myopes to hyperopes; in some embodiments from −20 Diopter to +20 Diopters. Second movable stage  1089  has a smaller motion range to provide an independent fogging motion; in some embodiments of up to 3 Diopters. 
     As a practical example, consider an exemplary case where the focal lengths of lenses  1083 ,  1084  and  1085  are 73, 45 and 30 mm, respectively. Moving second movable stage  1089  by 4.0 mm under control of the at least one processor  140  creates a fogging amount on the eye of 1.5 diopters. The magnifications calculated using the chief ray would indicate the image of target  1082  on the retina of eye  101  remained constant when second movable stage  1089  moved. However, if we consider a reasonable sized eye pupil diameter of 4 mm, the size of the image of target  1082  on the retina actually increases by 15% due to the blurring effect. 
     The Zemax analysis diagrams of  FIGS. 4A and 4B  illustrate the situation.  FIGS. 4A and 4B  illustrate paths of light rays propagating to the retina of eye  101  from target  1082  presented by fixation target systems  2000  and  3000  when target  1082  is in a first location with respect to eye  101 , and then moved further away from eye  101 . The curved line represents the cornea of eye  101 . The retina is to the right. 
     In  FIG. 4A  the overall image size is small when target  1082  is in focus on the retina.  FIG. 5A  illustrates the image  5082 A on the retina of eye  101  produced by target  1082  of fixation target systems  2000  and  3000  when target  1082  is in a first location with respect to eye  101  near its far focal point. Here it is assumed that target  1082  comprises a circle with a pair of cross-hairs which cross at the center of the circle. 
     When target  1082  is fogged as shown in  FIG. 4B , the image of target  1082  forms in front of the retina and the rays expand as they continue on and the overall illuminated region on the retina increases.  FIG. 5B  illustrates the image  5082 B on the retina of eye  101  produced by target  1082  of fixation target systems  2000  and  3000  when target  1082  is moved further away from eye  101  so as to produce fogging. It can be seen that image  5082 B is actually larger than image  5082 A due to the blurring. This creates the conflicting cues because the blur cues tell the brain that target  1082  has moved more distant from eye  101 , but the size of the image of target  1082  on the retina is a cue which tells the brain that target  1082  has moved closer to eye  101 . 
     For many people, these conflicting cues prevent eye  101  from fully relaxing its accommodation. Because autorefractors and aberrometers are not completely reliable in fully relaxing the accommodation of a significant percentage of patients&#39; eyes, the resulting refraction measurements are often erroneous or inaccurate. 
     To address one or more of these issues, the inventors have conceived and developed a fixation target system  6000  which is illustrated in  FIG. 6 . 
     Fixation target system  6000  includes a first lens  1083  and a first movable stage  1088  on which second lens  1084  is disposed or mounted. Fixation target system  6000  also includes second movable stage  1089  which is disposed or mounted on first movable stage  1088 . Second lens  1084  is disposed or mounted on first movable stage  1088 , while third lens  1085  and fixation target  1082  are both disposed or mounted on second movable stage  1089 . First lens  1083  is not disposed or mounted on first movable stage  1088  or second movable stage  1089 . In fixation target system  6000 , eye  101  is located one focal length from first lens  1083 . 
     In fixation target system  6000 , the distance between second lens  1084  and third lens  1085  is less than f 2 , where f 2  is the focal length of second lens  1084 . In this arrangement, light rays that reach eye  101  are non-telecentric when they leave target  1082 . 
       FIGS. 7A and 7B  illustrate images on the retina of eye  101  produced by target  1082  of fixation target system  6000  when target  1082  is in a first location with respect to eye  101 , and then moved further away from eye  101 . In particular,  FIG. 7A  illustrates the image  7082 A on the retina of eye  101  produced by target  1082  of fixation target system  6000  when target  1082  is in a first location with respect to eye  101  near its far focal point.  FIG. 7B  illustrates the image  7082 B on the retina of eye  101  produced by target  1082  of fixation target system  6000  when target  1082  is moved further away from eye  101  so as to produce fogging. It can be seen that image  7082 B is smaller than image  7082 A, reinforcing the cue caused by the blurring of the image of target  1082 , which tells the brain that target  1082  moved more distant from eye  101 . 
     As before, consider as a practical example an exemplary case where the focal lengths of lenses  1083 ,  1084  and  1085  are 73, 45 and 30 mm, respectively. Moving second movable stage  1089  by 4.1 mm under control of the at least one processor  1040  creates a fogging amount on the eye of 1.5 diopters. The magnifications calculated using the chief ray would indicate the image of target  1082  on the retina of eye  101  remained constant when second movable stage  1089  moved. However, in this case, if we consider a reasonable sized eye pupil diameter of 4 mm, the size of the image of target  1082  on the retina, including blurred rays, decreases by 15%. 
     Because the cues are now consistent, a larger percentage of patient eyes  101  will fully relax accommodation during refraction measurements by wavefront aberrometer  1000 . 
     Other arrangements of optics in lieu of the arrangement of first, second, and third lenses  1083 ,  1084  and  1085  shown in  FIG. 6  may create the situation that the rays leaving the target  1082  are non-telecentric, thereby producing the desirable result of a smaller image of target  1082  on the retina of eye  101  as target  1082  is moved further away from eye  101 . However fixation target system  6000  exemplifies a particularly simple arrangement which lends itself to good image quality. 
     In other embodiments, second lens  1084  and third lens  1085  can be combined in a single lens. However, the use of two separate lenses will generally maintain high image quality. In some embodiments, second and third lenses  1084  and  1085  comprise two achromatic doublets with the more curved sides facing each other. 
     In another embodiment, a fixation target system may include a video display disposed or mounted on the second movable stage, wherein the fixation target is provided via the video display, and wherein the at least one processor  1040  is configured to electronically make the size of the fixation target on the video display smaller while moving the second movable stage to the second stage position which is more distant from eye  101 . 
       FIG. 8  is a flowchart of an example embodiment of a method  8000  of measuring one or more characteristics of eye  101  with a wavefront aberrometer such as wavefront aberrometer  1000  and fixation target system  6000 . 
     An operation  8005  includes aligning a measurement instrument, including the wavefront aberrometer  1000 , to eye  101  to be measured. 
     An operation  8010  includes activating a fixation target system, such as fixation target system  6000  for patient fixation on target  1082 . 
     An operation  8015  includes the at least one processor  1040  moving first movable stage  1088  with respect to eye  101  to a first stage position where fixation target  1082  draws a focus of eye  101  to near its far point (e.g., within one diopter of its far point). 
     An operation  8020  includes stopping movement of first movable stage  1088  with respect to eye  101  at the first stage position. 
     An operation  8025  includes, while first movable stage  1088  is stopped, moving second movable stage  1089  with respect to first movable stage  1088  and eye  101  to a second stage position where fixation target  1082  is moved away from eye  101  by an additional amount (e.g., 1.5 diopters) such that blur cues of fixation target  1082  indicate to the subject that fixation target  1082  is moving away from eye  101  at a same time that a size of an image of fixation target  1082  on the retina of eye  101  decreases. 
     An operation  8030  includes flashing a probe light beam, and causing wavefront sensor  1020  to measures refraction of eye  101 . 
     The principles of wavefront aberrometer  1000  including a fixation target system such as fixation target system  6000 , and an associated method of operation, as described above, may be applied to an optical measurement instrument which includes additional functionality, such as the ability to measure corneal topography and/or to make optical coherence tomography (OCT) measurements of interior structures of the eye. Embodiments of such an optical measurement instrument, and methods of operation thereof, will now be described. 
     As shown in  FIGS. 9A-9C , an optical measurement system  1 , according to many embodiments, is operable to provide for a plurality of measurements of the human eye, including wavefront aberrometry measurements, corneal topography measurements, and optical coherence tomography measurements to measure characteristics of the cornea, the lens capsule, the lens and the retina. Optical measurement system  1  includes a main unit  2  which comprises a base  3  and includes many primary subsystems of many embodiments of the system  1 . For example, externally visible subsystems include a touch-screen display control panel  7 , a patient interface assembly  4  and a joystick  8 . 
     Patient interface  4  may include one or more structures configured to hold a patient&#39;s head in a stable, immobile and comfortable position during the diagnostic measurements while also maintaining the eye of the patient in a suitable alignment with the diagnostic system. In a particularly preferred embodiment, the eye of the patient remains in substantially the same position relative to the diagnostic system for all diagnostic and imaging measurements performed by the system  1 . 
     In one embodiment the patient interface includes a chin support  6  and/or a forehead rest  4  configured to hold the head of the patient in a single, uniform position suitably aligned with respect to the system  1  throughout the diagnostic measurement. As shown in  FIG. 9C , the optical measurement system  1  may be disposed so that the patient may be seated in a patient chair  9 . Patient chair  9  can be configured to be adjusted and oriented in three axes (x, y, and z) so that the patent&#39;s head can be at a suitable height and lateral position for placement on the patient interface. 
     In many embodiments, the system  1  may include external communication connections. For example, the system  1  can include a network connection (e.g., an RJ45 network connection) for connecting the system  1  to a network. The network connection can be used to enable network printing of diagnostic reports, remote access to view patient diagnostic reports, and remote access to perform system diagnostics. The system  1  can include a video output port (e.g., HDMI) that can be used to output video of diagnostic measurements performed by the system  1 . The output video can be displayed on an external monitor for, for example, viewing by physicians or users. The output video can also be recorded for, for example, archival purposes. The system  1  can include one or more data output ports (e.g., USB) to enable export of patient diagnostic reports to, for example, a data storage device or a computer readable medium, for example a non-volatile computer readable medium, coupled to a laser cataract surgery device for use of the diagnostic measurements in conducting laser cataract surgeries. The diagnostic reports stored on the data storage device or computer readable medium can then be accessed at a later time for any suitable purpose such as, for example, printing from an external computer in the case where the user without access to network based printing or for use during cataract surgery, including laser cataract surgery. 
       FIG. 10  is a block diagram of a system including an optical measurement instrument  1  according to one or more embodiments described herein. Optical measurement instrument  1  includes: an optical coherence tomographer (OCT) subsystem  10 , a wavefront aberrometer subsystem  20 , and a corneal topographer subsystem  30  for measuring one or more characteristics of a subject&#39;s eye. Optical measurement instrument  1  may further include an iris imaging subsystem  40 , a fixation target subsystem  50 , a controller  60 , including one or more processor(s)  61  and memory  62 , a display  70  and an operator interface  80 . Optical measurement instrument  1  further includes a patient interface  4  for a subject to present his or her eye for measurement by optical measurement instrument  1 . 
     The optical coherence tomography subsystem  10  is configured to measure the spatial disposition (e.g., three-dimensional coordinates such as X, Y, and Z of points on boundaries) of eye structures in three dimensions. Such structure of interest can include, for example, the anterior surface of the cornea, the posterior surface of the cornea, the anterior portion of the lens capsule, the posterior portion of the lens capsule, the anterior surface of the crystalline lens, the posterior surface of the crystalline lens, the iris, the pupil, the limbus and/or the retina. The spatial disposition of the structures of interest and/or of suitable matching geometric modeling such as surfaces and curves can be generated and/or used by the controller for a number of purposes, including, in some embodiment to program and control a subsequent laser-assisted surgical procedure. The spatial disposition of the structures of interest and/or of suitable matching geometric modeling can also be used to determine a wide variety of parameters. 
     As a non-limiting example, the system  1  can be configured to use a swept source OCT imaging system employing wavelengths of around 1060 nm with an 8 mm scan depth. The spatial disposition of the eye structures using optical coherence tomography should generally be measured while the patient is engaged with patient interface  4 . The OCT scan depth may be between 8 and 50 mm, and the scan depth may be greater than about 24 mm or even 30 mm to achieve a full eyescan depth. The swept source wavelengths can be centered at wavelengths from 840 nm to 1310 nm. 
     Optical coherence tomographer subsystem  10  is only one example of an eye structure imaging subsystem which may be employed in optical measurement instrument  1 . In other embodiments, a different eye structure imaging subsystem may be employed, for example a Scheimplug Imager, a fluorescence imager, a structured lighting imager, a wavefront tomographer, an ultrasound imager and a plenoptic imager. 
     The wavefront aberrometer subsystem  20  is configured to measure ocular aberrations, which may include low and high order aberrations, by measuring the wavefront emerging from the eye by, for example a Shack Hartman sensor. 
     The corneal topographer subsystem  30  may apply any number of modalities to measure the shape of the cornea including one or more of a keratometry reading of the eye, a corneal topography of the eye, an optical coherence tomography of the eye, a Placido disc topography of the eye, a reflection of a plurality of points from the cornea topography of the eye, a grid reflected from the cornea of the eye topography, a Hartmann-Shack measurement of the eye, a Scheimpflug image topography of the eye, a confocal tomography of the eye, a Helmholtz source topographer, or a low coherence reflectometry of the eye. The shape of the cornea should generally be measured while the patient is engaged with patient interface  4 . 
     Fixation target system  50  is configured to control the patient&#39;s accommodation, as described above. In some embodiments, fixation target system  50  may be implemented by fixation target system  1080 . 
     Images captured by the corneal topographer subsystem  10 , the wavefront aberrometer  20 , the optical coherence tomographer subsystem  30  or the camera  40  may be displayed with a display of the operator interface  80  of the optical measurement system  2  or the display  70  of the optical measurement system, respectively. The operator interface may also be used to modify, distort, or transform any of the displayed images. 
     The shared optics  55  provide a common propagation path that is disposed between the patient interface  4  and each of the optical coherence tomographer (OCT) subsystem  10 , the wavefront aberrometer subsystem  20 , the corneal topographer subsystem  30 , and in some embodiments, the camera  40 , and the fixation target  50 . In many embodiments, the shared optics  55  may comprise a number of optical elements, including mirrors, lenses and beam combiners to receive the emission from the respective subsystem to the patient&#39;s eye and, in some cases, to redirect the emission from a patient&#39;s eye along the common propagation path to an appropriate director. 
     The controller  60  controls the operation of the optical measurement instrument  1  and can receive input from any of the optical coherence tomographer (OCT) subsystem  10 , the wavefront aberrometer subsystem  20 , the corneal topographer subsystem  30  for measuring one or more characteristics of a subject&#39;s eye, the camera  40 , the fixation target  50 , the display  70  and the operator interface  80  via the communication paths  58 . The controller  60  can include any suitable components, such as one or more processor, one or more field-programmable gate array (FPGA), and one or more memory storage devices. In many embodiments, the controller  60  controls the display  70  to provide for user control over the laser eye surgery procedure for pre-cataract procedure planning according to user specified treatment parameters as well as to provide user control over the laser eye surgery procedure. The communication paths  58  can be implemented in any suitable configuration, including any suitable shared or dedicated communication paths between the controller  60  and the respective system components. 
     The operator interface  80  can include any suitable user input device suitable to provide user input to the controller  60 . For example, the user interface devices  80  can include devices such as joystick  8 , a keyboard or a touchscreen display  70 . 
       FIGS. 11A and 11B  are simplified block diagrams illustrating an assembly  100  according to many embodiments which may be included in system  1 . The assembly  100  is a non-limiting example of suitable configurations and integration of the optical coherence tomographer (OCT) subsystem  190 , the wavefront aberrometer subsystem  150 , the corneal topographer subsystem  140  for measuring one or more characteristics of a subject&#39;s eye, a camera  40 , the fixation target subsystem  180  and the shared optics. 
     The shared optics generally comprise one or more components of a first optical system  170  disposed along a central axis  102  passing through the opening or aperture  114  of the structure  110 . A first optical system  170  directs light from the various light sources along the central axis  102  towards the eye and establishes a shared or common optical path along which the light from the various light sources travel to the eye  101 . In one embodiment, optical system  170  comprises a quarter wave plate  171 , a first beamsplitter  172 , a second beamsplitter  173 , an optical element (e.g., a lens)  174 , a second lens  175 , a third beamsplitter  176 , and a structure including an aperture  178 . Additional optical systems may be used in assembly  100  to direct light beams from one or more light sources to the first optical system  170 . For example, a second optical system  160  directs light to the first optical system  170  from the wavefront aberrometer subsystem  150  and comprises mirror  153 , beam splitter  183  and lens  185 . 
     Other configurations of the assembly  100  may be possible and may be apparent to a person of skill in the art. 
     The corneal topographer subsystem  140  comprises a structure  110  having a principal surface  112  with an opening or aperture  114  therein; a plurality of first (or peripheral) light sources  120  provided on the principal surface  112  of the structure  110 ; a Helmholz light source  130 ; and a detector, photodetector, or detector array  141 . 
     In one embodiment, structure  110  has the shape of an elongated oval or “zeppelin” with openings or apertures at either end thereof. An example of such a structure is disclosed in Yobani Meji&#39;a-Barbosa et al., “Object surface for applying a modified Hartmann test to measure corneal topography,” APPLIED OPTICS, Vol. 40, No. 31 (Nov. 1, 2001) (“Meji&#39;a-Barbosa”). In some embodiments, principal surface  112  of structure  110  is concave when viewed from the cornea of eye  100 , as illustrated in  FIG. 11A . 
     In one embodiment where principal surface  112  is concave, principal surface  112  has the shape of a conical frustum. Alternatively, principal surface  112  may have a shape of hemisphere or some other portion of a sphere, with an opening or aperture therein. Also alternatively, principal surface  112  may have the shape of a modified sphere or conical frustum, with a side portion removed. Beneficially, such an arrangement may improve the ergonomics of assembly  100  by more easily allowing structure  110  to be more closely located to a subject&#39;s eye  100  without being obstructed by the subject&#39;s nose. Of course, a variety of other configurations and shapes for principal surface  112  are possible. 
     In the embodiment of  FIG. 11A , the plurality of first light sources  120  are provided on the principal surface  112  of structure  110  so as to illuminate the cornea of eye  101 . In one embodiment, light sources  122  may comprise individual light generating elements or lamps, such as light emitting diodes (LEDs) and/or the tips of the individual optical fibers of a fiber bundle. Alternatively, principal surface  112  of structure  110  may have a plurality of holes or apertures therein, and one or more backlight lamps, which may include reflectors and/or diffusers, may be provided for passing lighting through the holes to form the plurality of first light sources  120  which project light onto the cornea of eye  100 . Other arrangements are possible. 
     In another embodiment, structure  110  is omitted from assembly  100 , and the first light sources  120  may be independently suspended (e.g., as separate optical fibers) to form a group of first light sources  120  arranged around a central axis, the group being separated from the axis by a radial distance defining an aperture in the group (corresponding generally to the aperture  114  in the structure  110  illustrated in  FIG. 11A ). 
     In operation, a ray (solid line) from one of the first light sources  120  is reflected by the cornea and passes through optical system  170  (including aperture  178 ) to appear as a light spot on detector array  141 . It will be appreciated that this ray is representative of a small bundle of rays that make it through optical system  170  and onto detector array  141 , all of which will focus to substantially the same location on detector array  141 . Other rays from that first light source  120  are either blocked by the aperture  178  or are otherwise scattered so as to not pass through the optical system  170 . In similar fashion, light from the other first light sources  120  are imaged onto detector array  141  such that each one of first light sources  120  is imaged or mapped to a location on detector array  141  that may be correlated to a particular reflection location on the cornea of eye  100  and/or the shape of the cornea. Thus, detector array  141  detects the light spots projected thereon and provides corresponding output signals to a processor of controller  60  ( FIG. 10 ). The processor determines the locations and/or shape of the light spots on detector array  141 , and compares these locations and/or shapes to those expected for a standard or model cornea, thereby allowing the processor of controller  60  to determine the corneal topography. Alternatively, other ways of processing the spot images on detector array  141  may be used to determine the corneal topography of eye  101 , or other information related to the characterization of eye  101 . 
     Detector array  141  comprises a plurality of light detecting elements arranged in a two dimensional array. In one embodiment, detector array  141  comprises such a charge-coupled device (CCD), such as may be found in a video camera. However, other arrangements such as a CMOS array, or another electronic photosensitive device, may be employed instead. Beneficially, the video output signal(s) of detector array  141  are provided to processor  61  which processes these output signals as described in greater detail below. 
     Assembly  100  also comprises a Helmholtz light source  130  configured according to the Helmholtz principle. As used herein, the term “Helmholtz source” or “Helmholtz light source” means one or a plurality of individual light sources disposed such that light from each of the individual light sources passes through an optical element having optical power, reflects off of a reference or test object, passes through the optical element, and is received by a detector, wherein light from the Helmholtz source is used to determine geometric and/or optical information of at least a portion of a surface of the reference or test object. In general, it is a characteristic of Helmholtz sources that the signal at the detector is independent of the relative position of the test or reference object relative to the Helmholtz source. As used herein, the term “optical element” means an element that refracts, reflects, and/or diffracts light and has either positive or negative optical power. 
     In such embodiments, the Helmholtz light source  130  is located at optical infinity with respect to eye  100 . The Helmholtz principle includes the use of such infinite sources in combination with a telecentric detector system: i.e., a system that places the detector array at optical infinity with respect to the surface under measurement, in addition to insuring that the principal measured ray leaving the surface is parallel to the optical axis of the instrument The Helmholtz corneal measurement principle has the Helmholtz light source at optical infinity and the telecentric observing system so that detector array  141  is also optically at an infinite distance from the images of the sources formed by the cornea. Such a measurement system is insensitive to axial misalignment of the corneal surface with respect to the instrument. 
     In one embodiment, the Helmholtz light source  130  comprises a second light source  132  which may comprise a plurality of lamps, such as LEDs or optical fiber tips. In one embodiment, second light source  132  comprises an LED and a plate  133  with plurality of holes or apertures in a surface that are illuminated by one or more backlight lamps with an optical element  131 , which may comprise diffusers. 
     In one embodiment, second light sources  132  are located off the central optical axis  102  of assembly  100 , and light from second light sources  132  is directed toward optical element  171  by third beamsplitter  176 . 
     The operation of the topographer portion of system  100  may be conducted with the combined use of first light source  120  and the Helmholz light source  130 . In operation, detector array  141  detects the light spots projected thereon from both Helmholz light source  130  (detected at a central portion of detector array  141 ) and first light sources  120  (detected at a peripheral portion of detector array  141 ) and provides corresponding output signals to processor. In general, the images of first light sources  120  that appear on detector array  140  emanate from an outer region of the surface of the cornea, and the images of Helmholz light source  130  that appear on detector array  141  emanate from a central or paraxial region of the surface of the cornea. Accordingly, even though information about the central region of the corneal surface (e.g., surface curvature) cannot be determined from the images of first light sources  120  on detector array  141 , such information can be determined from the images of Helmholz light source  130  on detector array  141 . A processor of controller  60  determines the locations and/or shapes of the light spots on detector array  141 , and compares these locations and/or shapes to those expected based for a standard or model cornea, thereby allowing the processor to determine the corneal topography of eye  101 . Accordingly, the topography of the entire corneal surface can be characterized by system  100  without a “hole” or missing data from the central corneal region. 
     A fourth light source  201  off the central axis  102  may be directed along optical axis  102  by mirrors  177 ,  179  disposed on or near the aperture  178 , perpendicular to the optical axis  102  are configured as a pupil retroreflection illuminator. The pupil retroreflecton illuminator is configured to direct a disc of light toward a patient&#39;s eye, whereby the disc of light may be reflected from reflective surfaces within the eye, and the reflected light is transmitted by optical path  170  to detector  141 . The pupil retroreflection illuminators may optionally be configured such that, when a patient&#39;s pupil is dilated, the disc of light from light source  201  is reflected from an implanted IOL to image the IOL, including any fiducial marks; if IOL is imperfectly placed, detector  141  may be used to determine IOL edges are decentered. Also, images from detector  141  using the pupil retroreflection illuminator may see folds, for instance, unfolded edge if the IOL did not unfold properly. 
     The wavefront aberrometer subsystem  150  of the assembly  100  comprises a third (probe light beam) light source  152  providing a probe light beam and a wavefront sensor  155 . Wavefront aberrometer subsystem  150  may further comprise: a collimating lens  154 ; a polarizing beamsplitter  163 ; and an imaging system  166  comprising a first optical element, lens  163  and a second optical element, lens  164 , and a dynamic-range limiting aperture  165  for limiting a dynamic range of light provided to wavefront sensor  155  so as to preclude data ambiguity. Light from the wavefront aberrometer subsystem is directed to one of the constituent optical elements of the optical system  170  disposed along a central axis  102  passing through the opening or aperture  114  of the structure  110 . It will be appreciated by those of skill in the art that the lenses  163 ,  164 , or any of the other lenses discussed herein, may be replaced or supplemented by another type of converging or diverging optical element, such as a diffractive optical element. 
     Light source  152  may be an 840 nm SLD (super luminescent laser diode). An SLD is similar to a laser in that the light originates from a very small emitter area. However, unlike a laser, the spectral width of the SLD is very broad, about 40 nm. This tends to reduce speckle effects and improve the images that are used for wavefront measurements. 
     Wavefront sensor  155  may be a Shack-Hartmann wavefront sensor comprising a detector array and a plurality of lenslets for focusing received light onto its detector array. In that case, the detector array may be a CCD, a CMOS array, or another electronic photosensitive device. However, other wavefront sensors may be employed instead. Embodiments of wavefront sensors which may be employed in one or more systems described herein are described in U.S. Pat. No. 6,550,917, issued to Neal et al. on Apr. 22, 2003, and U.S. Pat. No. 5,777,719, issued to Williams et al. on Jul. 7, 1998, both of which patents are hereby incorporated herein by reference in their entirety. 
     The aperture or opening in the middle of the group of first light sources  120  (e.g., aperture  114  in principal surface  112  of structure  110 ) allows system  100  to provide a probe light beam into eye  101  to characterize its total ocular aberrations. Accordingly, third light source  152  supplies a probe light beam through polarizing beam splitter  162  to first beamsplitter  172  of optical system  170 . First beamsplitter  172  directs the probe light beam through aperture  114  to eye  101 . Beneficially, light from the probe light beam is scattered from the retina of eye  100 , and at least a portion of the scattered light passes back through aperture  114  to first beamsplitter  172 . First beamsplitter  172  directs the back scattered light back through beam splitter  172  to polarizing beamsplitter  183 , mirror  153 , adjustable focal length lens  179 , and ultimately to wavefront sensor  155 . 
     Wavefront sensor  155  outputs signals to a processor of controller/processor  60  which uses the signals to determine ocular aberrations of eye  101 , including measuring the refraction of eye  101 . Beneficially, controller/processor  60  may be able to better characterize eye  101  by considering the corneal topography of eye  101  measured by the corneal topography subsystem, which may also be determined by controller/processor  60  based on outputs of detector array  141 , as explained above. 
     In operation of the wavefront aberrometer subsystem  150 , light from light source  152  is collimated by lens  154 . The light passes through light source polarizing beam splitter  162 . The light entering light source polarizing beam splitter  162  is partially polarized. Polarizing beam splitter  162  reflects light having a first, S, polarization, and transmits light having a second, P, polarization so the exiting light is 100% linearly polarized. In this case, S and P refer to polarization directions relative to the hypotenuse in light source polarizing beam splitter  162 . 
     The light from polarizing beamsplitter  162  travels through adjustable focal length lens  179  and passes through toward beam splitter  153 , retaining its S polarization, and then travels through beamsplitter  183 , optical element (e.g., lens)  185 , beamsplitter  172  and  173 , and quarter wave plate  171 . Quarter wave plate  171  converts the light to circular polarization. The light then travels through aperture  114  in principal surface  112  of structure  110  to eye  101 . Beneficially, the beam diameter on the cornea may be between 1 and 2 mm. Then the light travels through the cornea and focuses onto the retina of eye  101 . 
     The focused spot of light becomes a light source that is used to characterize eye  101  with wavefront sensor  155 . Light from the probe light beam that impinges on the retina of eye  101  scatters in various directions. Some of the light reflects back as a semi-collimated beam back towards assembly  100 . Upon scattering, about 90% of the light retains its polarization. So the light traveling back towards assembly is substantially still circularly polarized. The light then travels through aperture  114  in principal surface  112  of structure  110 , through quarterwave plate  171 , and is converted back to linear polarization. Quarterwave plate  171  converts the polarization of the light from the eye&#39;s retina so that it is P polarized, in contrast to probe light beam having the S polarization. This P polarized light then reflects off of first beamsplitter  172 , and passes through optical element (e.g., lens)  185 , beamsplitters  183  and  153 , optical element (e.g., lens)  168  and reaches polarizing beamsplitter  162 . Since the light is now P polarized relative the hypotenuse of polarizing beamsplitter  162 , the beam is transmitted and then continues to imaging system  166  comprising first optical element  164  and second optical element (e.g., lens)  163 . The beam is also directed through a dynamic-range limiting aperture  165  for limiting a dynamic range of light provided to wavefront sensor  155  so as to preclude data ambiguity. 
     When wavefront sensor  155  is a Shack-Hartmann sensor, the light is collected by the lenslet array in wavefront sensor  155  and an image of spots appears on the detector array (e.g., CCD) in wavefront sensor  155 . This image is then provided to be processed by controller/processor  60  and analyzed to compute the refraction and aberrations of eye  101 . 
     The comprises a pre-correction system which compensates the probe light beam  153  to be injected into eye  101  for aberrations in eye  101  by adding a desired pre-correction for the injected probe light beam  153  by adding defocus that just compensates for the spherical equivalent defocus of eye  101  which is being measured. Movable stage  1130  may be moved in response to control signal  199  which may be provided from controller/processor  60 . 
     The same position of movable stage  1130  which corrects for the defocus aberrations of eye  101 , also ensures that the returned light arrives at a wavefront sensor  155  collimated to within the dynamic range of wavefront sensor  155 . Dynamic range limiting aperture  165  blocks any rays outside the angular dynamic range of the wavefront sensor  155  so that no mixing or measurement confusion occurs. When the wavefront sensor  155  is a Shack-Hartmann sensor, the focal spots cannot collide, interfere or cause confusion with adjacent focal spots. 
     Beneficially, controller/processor  60  moves movable stage  1130  to provide a desired characteristic to at least one of: probe light beam  153  injected into eye  101 , or the light received by wavefront sensor  155  from the retina of eye  101 . 
     The proper or desired adjusted focal length for movable stage  1130  may be determined in a number of ways. In some embodiments, an additional beam splitter may be provided in an optical path between imaging system  166  and wavefront sensor  155 , and a focusing lens and a detector may be used to create an image of the light incident upon the retina. In that case, the proper or desired adjusted focal length may determined by minimizing the spot size on the back of the retina, performed by comparing the spot sizes from different focal length values for adjustable focal length lens  169 . Beneficially eye  101  is arranged to be one focal length of objective lens  168 , and wavefront sensor  155  is arranged to be at the conjugate image plane to eye  101 . 
     Meanwhile, controller/processor  60  receives image data (“first image data”) from wavefront sensor  155  produced in response to the light returned from the retina of eye  101 , and processes the first image data to determine the refraction of eye  101 . 
     An OCT subsystem  190  of assembly  100  may comprise an OCT assembly  191 , and a third optical path  192  which directs the OCT beam of the OCT light source to the first optical path  170 . The third optical path  192  may comprise a fiber optic line  196 , for conducting the OCT beam from the OCT light source, a z-scan device  193  operable to alter the focus of the beam in the z-direction (i.e., along the direction of propagation of the OCT beam) under control of the controller, and x-scan device  195 , and a y-scan device  197  operable to translate the OCT beam in the x and y directions (i.e., perpendicular to the direction of propagation of the of the OCT beam), respectively, under control of the controller. The OCT light source and reference arm may be incorporated into the main unit  4  of the optical measurement instrument  1  shown in  FIG. 9A . Alternatively, the OCT assembly  191  may be housed in a second unit  200  and the OCT beam from the OCT source may be directed from the second housing  200  to the main unit by optical pathway  192 . 
     The OCT systems and methods of the optical measurement instruments and methods described herein may be FD-OCT (Fourier domain optical coherence tomography) systems, including either an SD-OCT (spectral domain optical coherence tomography) system or an SS-OCT (swept source optical coherence tomography) system. In conventional FD-OCT systems, the interference signal is distributed and integrated over numerous spectral wavelength intervals, and is inverse Fourier transformed to obtain the depth-dependent reflectivity profile of the sample. The profile of scattering as a function of depth is referred to as an A-scan (Axial-scan). The beam can be scanned laterally to produce a set of A-scans that can be combined together to form a tomogram of the sample (a B-scan). 
     In an SD-OCT system, various spectral wavelength intervals of the combined returned light from the reference and sample arms are spatially encoded using, for instance, a collimator, diffraction grating, and a linear detector array. Resampling of the data obtained from the linear detector array is performed in order to correct for the nonlinear spatial mapping of wavenumbers. After resampling and subtraction of the dc background, the depth profile structural information is obtained by performing the inverse Fourier transform operation. In swept-source OCT, the broad bandwidth optical source is replaced by a rapid-scanning laser source. By rapidly sweeping the source wavelength over a broad wavelength range, and collecting all the scattering information at each wavelength and at each position, the composition of the collected signal is equivalent to the spectral-domain OCT technique. The collected spectral data is then inverse Fourier transformed to recover the spatial depth-dependent information. 
     FD-OCT suffers from an inherent sample-independent limited depth range, typically between 1 and 5 mm. One limitation flows from the fact that FD-OCT extracts depth information from the inverse Fourier transform of a spectral interferogram. Since the spectral interferogram can only be recorded as a real signal, its Fourier transform is necessarily Hermitian symmetric about the zero path length difference (ZPD) position. As a result, the positive and negative displacements about the ZPD cannot be unambiguously resolved, which gives rise to mirror image artifacts and generally halves the useable range. This is referred to as the complex conjugate ambiguity. Another limitation is a sensitivity fall-off which results in reduced sensitivity with increasing depth. Moreover, since the signal in OCT is derived only from backscattered photons, optical attenuation from absorption and scattering generally result in a useable imaging depth of about 1-4 mm. 
     Several “full range” OCT techniques have been developed that eliminate the complex conjugate artifacts to effectively double the measurement range around the ZPD position. These full range OCT techniques result in useable imaging depths of up to about 5 mm up to about 8 mm. Suitable full range techniques are methods utilizing a dithering reference lag to break the phase ambiguity, methods that use phase distortion, and other suitable methods 
     As shown in  FIG. 12 , the OCT assembly  191  of OCT subsystem  190  includes a broadband or a swept light source  202  that is split by a coupler  204  into a reference arm  206  and a sample arm  210 . The reference arm  106  includes a module  108  containing a reference reflection along with suitable dispersion and path length compensation. The sample arm  110  of the OCT assembly  191  has an output connector  212  that serves as an interface to the rest of the optical measurement instrument. The return signals from both the reference and sample arms  206 ,  210  are then directed by coupler  204  to a detection device  220 , which employs either time-domain, frequency, or single point detection techniques. In  FIG. 12 , a swept source technique is used with a laser wavelength of 1060 nm swept over a range of 8-50 mm depth. 
       FIG. 13  is a schematic drawing of a human eye  400 . In many embodiments, a light beam  401  from a light source enters the eye from the left of  FIG. 13 , refracts into the cornea  410 , passes through the anterior chamber  404 , the iris  406  through the pupil, and reaches lens  402 . After refracting into the lens, light passes through the vitreous chamber  412 , and strikes the retina  476 , which detects the light and converts it to an electric signal transmitted through the optic nerve to the brain (not shown). The vitreous chamber  412  contains the vitreous humor, a clear liquid disposed between the lens  402  and retina  476 . As indicated in  FIG. 13 , cornea  410  has corneal thickness (CT), here considered as the distance between the anterior and posterior surfaces of the cornea. Anterior chamber  404  has anterior chamber depth (ACD), which is the distance between the anterior surface of the cornea and the anterior surface of the lens. Lens  402  has lens thickness (LT) which is the distance between the anterior and posterior surfaces of the lens. The eye has an axial length (AXL) which is the distance between the anterior surface of the cornea and the retina  476 .  FIG. 13  also illustrates that, in many subjects the lens, including the lens capsule, may be tilted at one or more angles relative to the optical axis, including an angle γ relative to the optical axis of the eye. 
     The optical system may also be arranged so that the movement pattern of the scan mirrors provides a lateral motion across the retina so that the shape of the retina may be determined. It is of particular interested to measure the shape and location of the depressed region of the retina named the foveal pit. When the patient is looking directly into the instrument, with their line of sight aligned to the fixation target, the foveal pit will be in center of the OCT lateral scan. This information is beneficial in that it informs the instrument operator if the patient was looking directly at the target when the measurement was made. Retinal scans are also useful in detecting disease conditions. In some cases there may be an absence of a foveal pit that also is considered an indication of a corneal abnormality. 
     The average axial length of the adult human eye is about 24 mm. Since the full range imaging depth of the OCT measurements are only about 5 mm to 8 mm, then OCT scanning may provide for OCT scans at different depths of the eye that can be combined together to form a combined OCT image of the eye. The OCT measurements may include OCT imaging at various depths of the patient&#39;s eye for imaging: (1) at least a portion of the retina, (2) at least a portion of the anterior portion of the eye, including at least a portion of the cornea (anterior and posterior), iris, and lens (anterior and posterior), and (3) performing axial eye length measurements. 
       FIGS. 14A-14C  illustrate various aspects of the OCT subsystem  190  according to various aspects of the present invention.  FIG. 14A  illustrates a preferred scanning region for the OCT subsystem according to many embodiments of the present invention. The scanning region may be defined from starting point  301  to ending point  302  at the anterior portion of the eye extending in a direction transverse the direction of propagation of the OCT beam and also extending in a direction parallel to an axis defining the axial length of the eye to the posterior portion  304  of the eye. The lateral scanning region should generally be sufficiently large in the lateral direction to permit imaging of the central portion of the cornea, at least a portion of the iris, at least a portion of the lens and at least of the retina. It should be noted that a region  303  between the posterior portion of the lens and the surface of the retina may optionally not be scanned by OCT subsystem  190  because the portion  330  does not contain anatomical structure for 3D analysis. 
       FIG. 15B  shows a representative graph of an intensity of an OCT signal of an OCT subsystem  190  according to many embodiments as a function of depth along the axis defining the axial length of the eye. The graph generally exhibits approximately four peaks having a complex structure: (1) a peak  310  having a doublet-like structure and generally corresponding to a location of the cornea; (2) a peak  320  having a doublet-like structure and generally corresponding to a location of an anterior surface of the lens; (3) a peak  330  having a complex structure generally corresponding to a location of a posterior surface of the lens; and (4) a peak  340  generally corresponding to a location of a retina. A distance between peak  310  and peak  340  can be used to calculate the axial length (AL) of the eye. An OCT scan by OCT subsystem  190 , including both an A-scan and B-scan, may be conducted for at least one location in the anterior portion of the eye (e.g., a location of a cornea, a location of an anterior surface of a lens and/or a location of a posterior surface of the lens) and at least one location in the posterior portion of the eye (e.g., at a location of a retina). In some embodiments, an OCT scan by the OCT subsystem  190 , including both an A-Scan and a B-scan is performed at a location corresponding to each of a location of the cornea, a location of an anterior surface of the lens, a location of a posterior surface of the lens, and a location corresponding to a retina. 
     It should be noted that because the OCT subsystem  190  provides for the detection of various structures of the eye, including a location of the cornea, the OCT subsystem  190  may be used as a ranging system to precisely align the patient in relation to the optical measurement system  1  of the present invention. The use of the OCT as a ranging system can significantly improve accuracy of corneal topography measurements, including keratometry measurements, which are sensitive to misalignment of the corneal structures. 
       FIG. 14C  shows a cross-section of an eye obtained by an optical measurement system of the present invention using an OCT subsystem according to the present invention. 
       FIG. 15  shows a 3 dimensional view of an eye obtained by an optical measurement system of the present invention using an OCT subsystem according to the present invention.  FIG. 15  evidences that the OCT subsystem of the present invention is operable to obtain biometry measurements according to the present invention, including the central corneal thickness (CCT), the anterior chamber depth (ACD), the radius of curvature of the anterior cornea (ROC AC ), the radius of curvature of the Posterior cornea (ROC PC ) and the Radius of curvature of the axial length (ROC AL ). 
     OCT subsystem  190  may provide sufficiently resolved structural information to a structural assessment that may provide a user with an indication of suitability of a particular patient for a laser cataract procedure. In one embodiment, an OCT scan performed by the OCT subsystem  190  at or near the retina (i.e., a retina scan) is sufficiently resolved to identify the foveal pit location and depth, wherein a lack of depression indicates an unhealthy retina. 
     In another embodiment, the optical measurement instrument  1  of the present invention provides one or more measurements sufficient to provide an assessment of the tear film of a patient. In one embodiment, the tear film assessment comprises a comparison of a wavefront aberrometry map and a corneal topography map or OCT map of the patient&#39;s eye, by, for instance, subtracting the corneal topography map from the wavefront aberrometry map, to obtain a difference map. A determination of whether the tear film is broken (if not smooth); an assessment of the tear film, including tear film breakup, can be obtained by reviewing the shape of spots on the topographer. For instance, a finding or indication that the tear film is disrupted, or broken, may be based upon the shape of a spot in that, if the spots are not round, and have, for instance, an oblong or broken up shape, it indicates that tear film is disrupted. The existence of such a disrupted tear film may indicate that K value, and other ocular measurements may not be reliable 
     In operation, as shown in  FIG. 11A , after exiting connector  212 , the OCT beam  214  may be collimated, for example using a collimating optical fiber  196 . Following collimating fiber  196  the OCT beam  214  is directed to an z-scan device  193  operable to change the focal point of the OCT beam in a z-direction, and x- and y-scan devices  195  and  197 , which are operable to scan the OCT beam in x and y-directions perpendicular to the z-direction. 
     Following the collimating optical fiber  196 , the OCT beam  214  continues through a z-scan device  193 ,  194 . The z-scan device may be a Z telescope  193 , which is operable to scan focus position of the laser pulse beam  66  in the patient&#39;s eye  101  along the Z axis. For example, the Z-telescope may include a Galilean telescope with two lens groups (each lens group includes one or more lenses). One of the lens groups moves along the Z axis about the collimation position of the Z-telescope  193 . In this way, the focus position in the patient&#39;s eye  101  moves along the Z axis. In general, there is a relationship between the motion of lens group and the motion of the focus point. The exact relationship between the motion of the lens and the motion of the focus in the z axis of the eye coordinate system does not have to be a fixed linear relationship. The motion can be nonlinear and directed via a model or a calibration from measurement or a combination of both. Alternatively, the other lens group can be moved along the Z axis to adjust the position of the focus point along the Z axis. The Z-telescope  84  functions as a z-scan device for changing the focus point of the OCT beam  214  in the patient&#39;s eye  101 . The Z-scan device can be controlled automatically and dynamically by the controller  60  and selected to be independent or to interplay with the X and Y scan devices described next. 
     After passing through the z-scan device, the OCT beam  214  is incident upon an X-scan device  195 , which is operable to scan the OCT beam  214  in the X direction, which is dominantly transverse to the Z axis and transverse to the direction of propagation of the OCT beam  214 . The X-scan device  195  is controlled by the controller  60 , and can include suitable components, such as a lens coupled to a MEMS device, a motor, galvanometer, or any other well-known optic moving device. The relationship of the motion of the beam as a function of the motion of the X actuator does not have to be fixed or linear. Modeling or calibrated measurement of the relationship or a combination of both can be determined and used to direct the location of the beam. 
     After being directed by the X-scan device  196 , the OCT beam  214  is incident upon a Y scan device  197 , which is operable to scan the OCT beam  214  in the Y direction, which is dominantly transverse to the X and Z axes. The Y-scan device  197  is controlled by the controller  60 , and can include suitable components, such as a lens coupled to a MEMS device, motor, galvanometer, or any other well-known optic moving device. The relationship of the motion of the beam as a function of the motion of the Y actuator does not have to be fixed or linear. Modeling or calibrated measurement of the relationship or a combination of both can be determined and used to direct the location of the beam. Alternatively, the functionality of the X-Scan device  195  and the Y-Scan device  197  can be provided by an XY-scan device configured to scan the laser pulse beam  66  in two dimensions transverse to the Z axis and the propagation direction of the laser pulse beam  66 . The X-scan and Y scan devices  195 ,  197  change the resulting direction of the OCT beam  214 , causing lateral displacements of OCT beam  214  located in the patient&#39;s eye  101 . 
     The OCT sample beam  214  is then directed to beam splitter  173  through lens  175  through quarter wave plate  171  and aperture  114  and to the patient eye  101 . Reflections and scatter off of structures within the eye provide return beams that retrace back through the patient interface quarter wave plate  171 , lens  175 , beam splitter  173 , y-scan device  197 , x-scan device  195 , z-scan device  193 , optical fiber  196  and beam combiner  204  ( FIG. 12 ), and back into the OCT detection device  220 . The returning back reflections of the sample arm  201  are combined with the returning reference portion  206  and directed into the detector portion of the OCT detection device  220 , which generates OCT signals in response to the combined returning beams. The generated OCT signals that are in turn interpreted by the controller  60  to determine the spatial disposition of the structures of interest in the patient&#39;s eye  101 . The generated OCT signals can also be interpreted by the controller to determine the spatial disposition of the structures of interest in the patient&#39;s eye  101 . The generated OCT signals can also be interpreted by the control electronics to align the position and orientation of the patient eye within the patient interface. 
     Optical measurement systems disclosed herein may comprise an iris imaging subsystem  40 . The imaging subsystem  40  generally may comprise an infrared light source, for example an infrared light source  152 , and detector  141 . In operation light from the light source  152  is directed along second optical path  160  to first optical path  170  and is subsequently directed to eye  101  as described above. Light reflected from the iris of eye  101  is reflected back along first optical path  170  to detector  141 . In normal use, an operator will adjust a position or alignment of system  100  in XY and Z directions to align the patient according to the image detector array  141 . In one embodiment of the iris imaging subsystem, eye  101  is illuminated with infrared light from light source  152 . In this way, the wavefront obtained by wavefront sensor  155  will be registered to the image from detector array  141 . 
     The image that the operator sees is the iris of eye  100 . The cornea generally magnifies and slightly displaces the image from the physical location of the iris. So the alignment that is done is actually to the entrance pupil of the eye. This is generally the desired condition for wavefront sensing and iris registration. 
     Iris images obtained by the iris imaging subsystem may be used for registering and/or fusing the multiple data sets obtained by the various subsystems of the present invention, by methods described for instance in “Method for registering multiple data sets,” U.S. patent application Ser. No. 12/418,841, which is incorporated herein by reference. As set forth in application Ser. No. 12/418,841, wavefront aberrometry may be fused with corneal topography, optical coherence tomography and wavefront, optical coherence tomography and topography, pachymetry and wavefront, etc. For instance, with image recognition techniques it is possible to find the position and extent of various features in an image. Regarding iris registration images, features that are available include the position, size and shape of the pupil, the position, size and shape of the outer iris boundary (OIB), salient iris features (landmarks) and other features as are determined to be needed. Using these techniques, both patient movement between measurements (and/or during a measurement sequence) can be identified, as well as changes in the eye itself (including those induced by the measurement, such as changes in the size of the pupil, changes in pupil location, etc.). 
     In many embodiments, an optical measurement system according the present includes a target fixation subsystem  50  ( FIG. 10 ), and an assembly  100  shown in  FIGS. 11A and 11B  includes fixation target subsystem  180  which includes optics  186  and a fixation target  182  for the patient to view. Fixation target subsystem  180  is used to control the patient&#39;s accommodation for wavefront aberrometry measurements, as described above, and because it is often desired to measure the refraction and wavefront aberrations when eye  100  is focused at its far point (e.g., because LASIK treatments are primarily based on this). In the fixation target subsystem  180 , a projection of target  182 , for instance a cross-hair pattern is projected onto the eye  101  of the patient, the cross hair pattern being formed, for example, by a backlit LED and a film. In other embodiments, target  182  may be formed on a video display device which is included in fixation target subsystem  180 . 
     In operation, light originates from the light source  152  or, alternatively, from video target backlight  182  and lens  186 . Lens  185  collects the light and forms an aerial image T 2 . This aerial image is the one that the patient views. The patient focus is maintained on aerial image  182  during measurement so as to maintain the eye in a fixed focal position. 
     The operating sequence the optical measurement system and methods of the present is not particularly limited. A scan of the patient&#39;s eye may comprise one or more of a wavefront aberrometry measurement of a patient&#39;s eye utilizing the wavefront aberrometry subsystem, a corneal topography measurement of a patient&#39;s eye and an OCT scan of the patient&#39;s eye using the OCT subsystem, wherein the OCT scan includes a scan at each or one or more locations within the eye of the patient. These locations of the OCT scan may correspond to the location of the cornea, the location of the anterior portion of the lens, the location of the posterior portion of the lens and the location of the retina. In a preferred embodiment, the operating sequence includes each of a wavefront aberrometry measurement, a corneal topography measurement and an OCT scan, wherein the OCT scan is taken at least at the retina, the cornea and one of anterior portion of the patient&#39;s lens. An iris image may be taken simultaneously with or sequentially with an each of measurements taken with wavefront aberrometry subsystem the corneal topography subsystem and the OCT subsystem, including an iris image take simultaneously with or sequentially with the location of each OCT scan. This results in improved accuracy in the 3-dimensional modeling of the patient&#39;s eye by permitting the various data sets to be fused and merged into a 3-dimensional model. 
       FIG. 10  shows one embodiment of an operating sequence and method in which wavefront aberrometry measurements, corneal topography measurements and OCT measurements are all taken. The optical measurement apparatus, including the method of  FIG. 10  may be used preoperatively, intra-operatively and/or postoperatively. In the method of  FIG. 10 , a step  801  comprises aligning the optical measurement system to the eye of the patent. A step  805  comprises activating the Target Fixation subsystem for patient fixation on target. A step  810  comprises activating the wavefront aberrometer subsystem such that the wavefront aberrometer light source  810  is activated and the eye refraction is measured via the wavefront sensor. A step  815  comprises activating the fixation target system to move the target to an optimum position and activate the wavefront aberrometer subsystem such that the wavefront aberrometer light source  152  is activated and the eye refraction is measured via the wavefront sensor  155 . A step  820  comprises obtaining an iris image using Iris Imaging Subsystem  40  while infrared light source  152  is operating. A step  825  comprises operating the z-scan device to set OCT scan location at or near cornea, and performing an OCT Scan with the OCT Subsystem. A step  830  comprises operating the z-scan device to set the OCT location at a location at or near the lens anterior and performing an OCT Scan with the OCT Subsystem. A step  835  comprises operating the z-scan device to set the OCT location at a location at or near the lens posterior and performing an OCT Scan with the OCT Subsystem. A step  840  comprises operating the X-scan device and Y-scan device so no light from OCT reaches detector  141 . A step  845  comprises obtaining an iris image using the Iris Imaging Subsystem while the infrared light source  152  flashes. A step  850  comprises obtaining an iris image using the Iris Imaging Subsystem while the light sources  120  and Helmholz source flash. A step  855  comprises measuring the corneal topography with the Corneal Topography Subsystem. A step  855  comprises operating the z-scan device to set the OCT location at a location at or near the retina and performing an OCT Scan with the OCT Subsystem. A step  860  comprises operating the X-scan device and Y-scan device so no light from OCT reaches detector  141 . An optional step  865  comprises measuring corneal topography with Corneal Topography Subsystem, which may provide for an improved 3D model of the patient eye. An optional step  870  comprises obtaining an iris image using Iris Imaging Subsystem (for 3D model). 
     The optical measurement instrument  1  and the optical measurements obtained therewith may be used pre-operatively, i.e. before a cataract surgery or other surgical procedure, for, e.g., eye biometry and other measurements, diagnostics and surgical planning. Surgical planning may include one or more predictive models. In the one or more predictive models, one or more characteristics of the postoperative condition of the patient&#39;s eye or vision is modeled based on one or more selected from the group consisting of pre-operative measurements obtained from the optical measurement instrument  1 , a contemplated surgical intervention, and on or more algorithms or models stored in the memory of the optical measurement system  1  and executed by the processor. The contemplated surgical intervention may include the selection of an IOL for placement, the selection of an IOL characteristic, the nature or type of incision to be used during surgery (e.g., relaxation incision), or one or more post-operative vision characteristics requested by the patient. 
     The optical measurement instrument  1  and the optical measurements obtained therewith may be used intra-operatively, i.e., during a cataract surgery or other surgical procedure, for, e.g., intraoperative eye diagnostics, determining IOL placement and position, surgical planning, and control/or of a laser surgical system. For instance, in the case of laser cataract surgical procedure, any measurement data obtained preoperatively by the optical measurement instrument may be transferred to a memory associated with a cataract laser surgical system for use before, during or after either the placement of a cap sulotomy, fragmentation or a patient&#39;s lens or IOL placement during the cataract surgery. In some embodiments, measurements using optical measurement instrument  1  may be taken during the surgical procedure to determine whether the IOL is properly placed in the patient&#39;s eye. In this regard, conditions measured during the surgical procedure may be compared to a predicted condition of the patient&#39;s eye based on pre-operative measurements, and a difference between the predicted condition and the actual measured condition may be used to undertake additional or corrective actions during the cataract surgery or other surgical procedure. 
     The optical measurement instrument  1  and the optical measurements obtained therewith may be used postoperatively, i.e., after a cataract surgery or other surgical procedure, for, e.g., post-operative measurement, postoperative eye diagnostics, postoperative IOL placement and position determinations, and corrective treatment planning if necessary. The postoperative testing may occur sufficiently after the surgery that the patient&#39;s eye has had sufficient time to heal and the patient&#39;s vision has achieved a stable, postsurgical state. A postoperative condition may be compared to one or more predicted condition performed pre-operatively, and a difference between the preoperatively predicted condition and the postoperatively measured condition may be used to plan additional or corrective actions during the cataract surgery or other surgical procedure. 
     The optical measurement instrument  1 , including the corneal topography subsystem, the OCT subsystem and the wavefront aberrometry subsystem, utilizing a suitable operating sequence as disclosed herein, is operable to measure one, more than one or all of the following: ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, posterior lens surface information, lens tilt information and lens position information. In some embodiments, the ocular biometry information may include a plurality of central corneal thicknesses (CCT), an anterior chamber depth (ACT), a pupil diameter (PD), a white to white distance (WTW), a lens thickness (LT), an axial length (AL) and a retinal layer thickness. This measurement data may be stored in memory  62  associated with controller  60 . The plurality of characteristics may be measured preoperatively, and where appropriate, intra-operatively, and postoperatively. 
     In some embodiments, memory  62  associated with controller  60  may store intraocular lens (IOL) model data for a plurality of IOL models, each of the IOL models having associated with it a plurality of predetermined parameters selected from the group consisting of dioptic power, refractive index, asphericity, toricity, haptic angulation and lens filter. The IOL data may be used by one or more processors of optical measurement instrument  1 , in conjunction with measurement data of a subject&#39;s eye obtained by optical measurement instrument  1 , for cataract diagnostics or cataract treatment planning, which may include specifying and/or selecting a particular IOL for a subject&#39;s eye. For example, one or more processors of optical measurement instrument  1  may execute an algorithm which includes: accessing the plurality of IOL models stored in, and for each of the IOL models: (1) modeling the subject&#39;s eye with an intraocular lens corresponding to the IOL model and the measured characteristics of the subject&#39;s eye; (2) simulating the subject&#39;s eye based on the plurality of IOL predetermined parameters and the predicted IOL position; (3) performing one of a ray tracing and a power calculation based on said model of the subject&#39;s eye; and (4) selecting an IOL for the subject&#39;s eye from the plurality of IOL models corresponding to the optimized IOL based on a predetermined criteria. 
     In some embodiments, one or more processors of optical measurement instrument  1  may execute an algorithm comprising: determining a desired postoperative condition of the subject&#39;s eye; empirically calculating a post-operative condition of the eye based at least partially on the measured eye characteristics; and predictively estimating, in accordance with an output of said empirically calculating and the eye characteristics, at least one parameter of an intraocular lens for implantation into the subject&#39;s eye to obtain the desired postoperative condition. 
     In many embodiments, the eye imaging and diagnostic system further comprises a memory operable to store Intraocular Lens (“IOL”) Data, the IOL data including a plurality of dioptic power, anterior and posterior radius, IOL thickness, refractive index, asphericity, toricity, echelette features, haptic angulation and lens filter. 
     In many embodiments, the eye imaging and diagnostic system further comprises a memory operable to store intraocular lens (“IOL”) model data for a plurality of IOL models, IOL model having associated with a plurality of predetermined parameters selected from the group consisting of dioptic power, anterior and posterior radius, IOL thickness, refractive index, asphericity, toricity, echelette features, haptic angulation and lens filter. 
     An improved system for selecting an intraocular lens (IOL) for implantation, comprises: a memory operable to store data acquired from each of the corneal topography subsystem, the wavefront sensor subsystem and the Optical Coherence Tomography subsystem, wherein the stored data includes a plurality of ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; the memory further operable to store intraocular lens (“IOL”) model data for a plurality of IOL models, IOL model having associated with it a plurality of predetermined parameters selected from the group consisting of dioptic power, anterior and posterior radius, IOL thickness, refractive index, asphericity, toricity, echelette features, haptic angulation and lens filter; and a processor coupled to the memory, the processor deriving the treatment of the eye of the patient applying, for each of the plurality of identified IOL Model, to: (1) predict a position of one of the identified IOL Models when implanted in the subject eye, based on the plurality of characteristics; (2) simulate the subject eye based on the plurality of IOL predetermined parameters and the predicted IOL position; (3) perform one or more of ray tracing and a IOL spherical equivalent (SE) and cylinder (C) power calculation, as well as optionally, to determine the optimum IOL orientation based on said eye model; and (4) propose one IOL power for one or more IOL models from the plurality of IOLs corresponding to the optimized IOL(s) based on predetermined criteria; and (5) show the simulated optical quality and/or visual performance provided by each of the proposed IOL models for distance and/or for any other vergence. 
     A method of selecting an intraocular lens (IOL) to be implanted in a subject&#39;s eye, comprising: measuring a plurality of eye characteristics comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; and for each of Intraocular Lens (“IOL”) model having associated with it a plurality of predetermined parameters selected from the group consisting of dioptic power, refractive index, anterior and posterior radius, IOL thickness, asphericity, toricity, echelette design, haptic angulation and lens filter: (1) modeling the subject eye with the intraocular lens; (2) simulating the subject eye based on the plurality of IOL predetermined parameters and the predicted IOL position; (3) performing a ray tracing and a IOL spherical equivalent (SE) and cylinder (C) power calculation, as well as determine the optimum IOL orientation based on said eye model; and (4) proposing one IOL power for one or more IOL models from the plurality of IOLs corresponding to the optimized IOL(s) based on predetermined criteria; and optionally (5) show the simulated optical quality and/or visual performance provided by each of the proposed IOL models for distance and/or for any other vergence. 
     A tangible computer-readable storage device storing computer instructions which, when read by a computer, cause the computer to perform a method comprising: receiving a plurality of eye characteristics comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; for each of Intraocular Lens (“IOL”) model having associated with it a plurality of predetermined parameters selected from the group consisting of dioptic power, refractive index, anterior and posterior radius, IOL thickness, asphericity, toricity, echelette design, haptic angulation and lens filter: (1) simulating a geometry of the subject eye with each of the plurality of intraocular lenses (IOL) implanted, in accordance with the plurality of eye characteristics; (2) performing a ray tracing and a IOL spherical equivalent (SE) and cylinder (C) power calculation, as well as optionally determining the optimum IOL orientation based on said eye model; (3) proposing one IOL power for one or more IOL models from the plurality of IOLs corresponding to the optimized IOL(s) based on predetermined criteria; and optionally (4) showing the simulated optical quality and/or visual performance provided by each of the proposed IOL models for distance and/or for any other vergence. 
     A method of predicting the intraocular lens position comprising: determining a plurality of eye characteristics before cataract surgery, comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; determining a plurality of eye characteristics after cataract surgery, comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; calculating or measuring, based on a mathematical relationship, a distance from the apex to a plane of the intraocular lens after an ocular surgical procedure; calculating an optical power of the intraocular lens suitable for providing a predetermined refractive outcome; wherein a mathematical relationship is found between the preoperative and postoperative eye characteristics that accurately predict the measured distance from the apex to the plane where the intraocular lens is. 
     An improved system for planning a refractive treatment of an eye of a patient, the system comprising: a memory operable to store eye measurement data comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; a processor coupled to the memory, the processor deriving the treatment of the eye of the patient applying an effective treatment transfer function, wherein the effective treatment transfer function is derived from, for each of a plurality of prior eye treatments, a correlation between a pre-treatment vector characterizing the eye measurement data before treatment, and a post-treatment vector characterizing post-treatment eye measurement data of the associated eye; an output coupled to the processor so as to transmit the treatment to facilitate improving refraction of the eye of the patient. The processor may comprise tangible media embodying machine readable instructions for implementing the derivation of the treatment. 
     A method for planning a refractive treatment of an eye of a patient, comprises: measuring a plurality of ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information. 
     A method of customizing at least one parameter of an intraocular lens, comprises: measuring a plurality of eye characteristics comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; determining a desired postoperative condition of the eye; empirically calculating a post-operative condition of the eye based at least partially on the measured eye characteristics; and predictively estimating, in accordance with an output of said empirically calculating and the eye characteristics, the at least one parameter of the intraocular lens to obtain the desired postoperative condition. 
     A method of adjusting the refractive power in an eye of a patient who has undergone cataract surgery comprises: measuring a plurality of post-operative eye characteristics in an eye of a patient who has previously undergone cataract surgery, the eye characteristics comprising ocular biometry information, anterior corneal surface information, posterior corneal surface information, anterior lens surface information, and posterior lens surface information, lens tilt information and lens position information; identifying a plurality of corrective procedure based at least partially on one of (1) a comparison of at least one measured pre-operative eye characteristic and the corresponding measured post-operative eye characteristic; and (2) a comparison of at least one predicted post-operative eye characteristic and the corresponding measured post-operative eye characteristic; for each of a plurality of corrective procedures: modeling the subject eye with the corrective procedure; modeling the subject eye based on the corrective procedure; performing one of a ray tracing and a power calculation based on said eye model; and selecting a corrective procedure from the plurality of IOL models corresponding to the optimized IOL based on a predetermined criteria. 
     In some embodiments, the system further comprises a processor configured to execute an algorithm. The algorithm comprises, for each of the IOL models: (1) modeling the subject&#39;s eye with an intraocular lens corresponding to the IOL model and the measured characteristics of the subject&#39;s eye; (2) simulating the subject&#39;s eye based on the plurality of IOL predetermined parameters and the predicted IOL position; (3) performing one of a ray tracing and a power calculation based on said model of the subject&#39;s eye; and (4) selecting an IOL from the plurality of IOL models corresponding to the optimized IOL based on a predetermined criteria. 
     This summary and the following detailed description are merely exemplary, illustrative, and explanatory, and are not intended to limit, but to provide further explanation of the invention as claimed. Additional features and advantages of the invention will be set forth in the descriptions that follow, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description, claims and the appended drawings. 
     All patents and patent applications cited here are hereby incorporated by reference hereby reference in their entirety. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated here or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values here are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described here can be performed in any suitable order unless otherwise indicated here or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention, and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     While certain illustrated embodiments of this disclosure have been shown and described in an exemplary form with a certain degree of particularity, those skilled in the art will understand that the embodiments are provided by way of example only, and that various variations can be made and remain within the concept without departing from the spirit or scope of the invention. Such variations would become clear to one of ordinary skill in the art after inspection of the specification, drawings and claims herein. Thus, it is intended that this disclosure cover all modifications, alternative constructions, changes, substitutions, variations, as well as the combinations and arrangements of parts, structures, and steps that come within the spirit and scope of the invention as generally expressed by the following claims and their equivalents.