Abstract:
An apparatus and method for actively compensating for pupil centroid shift includes obtaining a first measurement of a first reference point relative to a predetermined reference frame, wherein the first reference point being associated with a first pupil diameter of a patient. The method further includes obtaining a second measurement of a second reference point relative to the predetermined reference frame, wherein the second reference point is associated with a second pupil diameter of the patient and the second pupil diameter is different from the first pupil diameter. The method still further includes actively determining a relationship between the first measurement and the second measurement and actively generating a correction in response to the relationship, wherein the correction being used by a treatment laser in association with an eye surgery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/328,414, filed on Apr. 27, 2010. The entire disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to vision correction systems and methods and more particularly to pupil centroid shift compensation systems and methods. 
       BACKGROUND AND SUMMARY 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Vision correction treatments generally treat the cornea of an eye to correct one or more refractive errors of the eye. For example only, a laser may be used to treat the cornea in laser-assisted in situ keratomileusis (LASIK), laser-assisted sub-epethilial keratectomy (LASEK), and photorefractive keratectomy (PRK) vision correction treatments. 
         [0005]    Prior to the treatment, an optical measuring device, such as a refractometer (e.g., an auto-refractor, a pupilometer, etc.) or an aberrometer (e.g., a wavefront aberrometer), may be used to measure refractive errors and aberrations of the optical system. The refractometer or aberrometer may also determine one or more parameters, such as pupil centroid. A treatment plan for the procedure may be generated based on data from such optical measuring devices, like the aberrometer, and other data. 
         [0006]    Pupil centroid may refer to a center location of the pupil of the eye with respect to a reference location. The reference location may include, for example, a center location of the pupil when fully dilated, a center of an outside of the cornea of the eye, or another suitable reference location. The pupil centroid may be expressed two-dimensionally (e.g., X and Y) with respect to the reference location. The pupil centroid may be expressed three-dimensionally in various implementations (e.g., X, Y, and Z) with respect to the reference location. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0008]      FIG. 1  is an exemplary illustration of an eye according to the principles of the present disclosure; 
           [0009]      FIG. 2  is an exemplary illustration of pupil centroid shift according to the principles of the present disclosure; 
           [0010]      FIG. 3  is an exemplary illustration of a vision correction procedure that is centered versus a vision correction procedure that is decentered according to the principles of the present disclosure; 
           [0011]      FIG. 4  is a functional block diagram of an exemplary pupil centroid shift determination and storage system according to the principles of the present disclosure; 
           [0012]      FIG. 5  is an exemplary graph of pupil centroid shift as a function of pupil size and an exemplary illustration of pupil size and pupil centroid shift as functions of light intensity according to the principles of the present disclosure; 
           [0013]      FIG. 6  is a functional block diagram of an exemplary vision treatment system according to the principles of the present disclosure; and 
           [0014]      FIG. 7  is a flowchart depicting an exemplary method of accounting for pupil centroid shift in real time during a vision correction treatment according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0016]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0017]    Referring now to  FIG. 1 , an exemplary image  100  of a human eye is presented. Among other things, the eye includes an iris  102  and a pupil  106 . The pupil  106  is an aperture in the iris  102 . While not numbered, a cornea covers the iris  102  and the pupil  106 . A vision correction treatment, such as a laser-assisted in situ keratomileusis (LASIK) treatment, a laser-assisted sub-epethilial keratectomy (LASEK) treatment, a photorefractive keratectomy (PRK) treatment, or another suitable type of vision correction treatment may treat the cornea or treat a lens within the pupil. 
         [0018]    More specifically, a vision correction treatment may involve treating one or more portions of the cornea. For purposes of discussion only, exemplary circular trace  110  may be said to correspond to an outside of the iris  102 . However, the exemplary circular trace  110  may correspond to a limbus of the eye (i.e., a border where the cornea and a sclera meet). Exemplary plus-shaped mark  114  may correspond to a center location of the circular trace  110  (i.e., the center of the iris  102 ). Exemplary diamond-shaped mark  116  may correspond to a line of sight. For purposes of discussion only, exemplary circular trace  118  may be said to correspond to an outer perimeter of the pupil  106 , but the circular trace  118  may also correspond to an inner perimeter of the iris  102 . Exemplary plus-shaped mark  122  may correspond to a center location of the circular trace  114  (i.e., the center of the pupil  106 ). 
         [0019]    Pupil centroid may refer to a center location of the pupil  118  with respect to a first reference location. For example only, the first reference location may be the center of the iris  110  or another suitable reference location. 
         [0020]    The pupil centroid may be expressed as a multi-dimensional coordinate that relates the center of the pupil  118  to the first reference location. For example only, the pupil centroid may be expressed as a two-dimensional coordinate (e.g., X and Y) or a three-dimensional coordinate (e.g., X, Y, and Z) that relates the center of the pupil to the first reference location. The pupil centroid may be expressed in three-dimensions, for example, to account for parallax. 
         [0021]    Referring now to  FIG. 2 , an exemplary illustration of pupil centroid shift is presented. During performance of a vision correction treatment, a laser or another treatment device may be centered based on the pupil centroid. However, it has been found that the pupil centroid may vary with pupil dilation, constriction, and/or other factors. For example only, the pupil centroid may generally move nasally (i.e., toward the nose) and/or superiorily (i.e., upward) as the pupil  106  constricts. Pupil constriction maybe referred to as miosis. 
         [0022]    The example of  FIG. 2  includes exemplary illustrations of the pupil  106  when dilated to first and second degrees of dilation  202  and  206 , respectively. When dilated to the first degree of dilation  202 , the pupil  106  is dilated to a greater extent than it is when dilated to the second degree of dilation  206 . 
         [0023]    The pupil centroid when the pupil  106  is dilated to the first degree of dilation  202  is illustrated by first X-shaped mark  210 . The pupil centroid when the pupil  106  is dilated to the second degree of dilation  206  is illustrated by second X-shaped mark  214 . Exemplary asterisk-shaped marks  218  may correspond to the first reference location, such as the center of the iris  110 . 
         [0024]    As can be seen from the example of  FIG. 2 , the pupil centroid  210  when the pupil  106  is dilated to the first degree of dilation  202  may be approximately 0.1 units in the X direction (i.e., 6.7−6.6), and the pupil centroid  214  when the pupil  106  is dilated to the second degree of dilation  206  may be approximately 0.4 units in the X direction (i.e., 6.7−6.3). 
         [0025]    A location of the pupil centroid with respect to a second reference location may be referred to as pupil centroid shift. In other words, the pupil centroid shift may refer to a difference between the second reference location and the location of the pupil centroid. For example only, the second reference location may be the pupil centroid when the pupil  106  is fully dilated (e.g., taken before treatment) or another suitable reference location. The pupil centroid shift may be expressed as a multi-dimensional coordinate that relates the center of the pupil  118  to the second reference location. For example only, the pupil centroid shift may be expressed as a two-dimensional coordinate (e.g., X and Y) or a three-dimensional coordinate (e.g., X, Y, and Z) that relates the center of the pupil  118  to the second reference location. In the example of  FIG. 2 , assuming that the pupil centroid  210  corresponds to the second reference location, the pupil centroid shift may be approximately 0.3 units in the X direction (i.e., 0.4−0.1). 
         [0026]    Failure to account for the pupil centroid shift associated with the varying pupil size during a vision correction treatment may result in the treatment being de-centered. A de-centered treatment may render a result of the vision correction treatment less than optimal inducing aberrations or imperfections. For example only, the pupil  106  may expand or contract during the treatment as the patient attempts to focus on a fixation target, as the emotional state of the patient changes (e.g., fear), as lighting conditions vary, and/or as one or more other conditions occur. An exemplary illustration of a centered treatment  302  versus a de-centered treatment  306  is presented in the example of  FIG. 3 . 
         [0027]    Referring now to  FIG. 4 , a functional block diagram of an exemplary pupil centroid shift determination and storage system  400  is presented. In various implementations, the pupil centroid shift determination and storage system  400  may be implemented with any device that can measure pupil size, such as a pupilometer, refractometer, or an aberrometer (e.g., a wavescan), with a treatment device that contains the necessary measuring hardware (e.g., a laser), with another suitable device, and/or independently. 
         [0028]    An illumination control module  402  controls an intensity of light provided to the eye by a light source  406 . For example only, the light source  406  may include one or more light emitting diodes (LEDs) and/or other suitable light sources. The illumination control module  402  may control the intensity of the light in a predetermined profile. For example only, the illumination control module  402  may vary the intensity of the light from a predetermined minimum intensity to a predetermined maximum intensity and back to the predetermined minimum intensity, vice versa, or in another suitable profile. The predetermined minimum intensity may correspond to a lighting condition that will cause the pupil  106  to be fully dilated. In other words, the predetermined minimum intensity may correspond to a lighting condition that will create a greatest pupil size. In contrast, the predetermined maximum intensity may correspond to a lighting condition that will cause the pupil  106  to constrict to a greatest extent. In other words, the predetermined maximum intensity may correspond to a lighting condition that will create a smallest pupil size. Varying the intensity of the light from the predetermined minimum intensity to the predetermined maximum intensity and back to the predetermined minimum intensity or vice versa may enhance a result of the treatment by predicting an associated pupil centroid shift to better maintain the orientation of the treatment laser relative to the patient&#39;s cornea. More specifically, as the patient&#39;s pupil size varies (i.e., increases or decreases), the proper frame of reference of the treatment laser can be maintained based on the pupil centroid and the associated pupil centroid shift. 
         [0029]    The illumination control module  402  may vary the intensity in predetermined steps. For example only, the illumination control module  402  may increment or decrement the intensity of the light by a predetermined amount for each change in the intensity. The predetermined amount may correspond to a minimum lighting condition change that may create a measurable change (e.g., 0.01 mm) in pupil size. 
         [0030]    The illumination control module  402  may trigger an imaging module  410  when the intensity of the light has been constant for at least a predetermined period. The predetermined period may correspond to a period of time after a change in the intensity at which the pupil size may be in a steady-state condition. The imaging module  410  may capture an image of the eye when triggered by the illumination control module  402 . For example only, the image may be similar to the example of  FIG. 1 . The illumination control module  402  may increment or decrement the intensity of the light to a next intensity after the imaging module  410  captures the image. In this manner, the imaging module  410  may capture an image for each measurable pupil size. 
         [0031]    A pupil centroid determination module  414  may determine the pupil centroid based on the image. The pupil centroid determination module  414  may determine the pupil centroid based on, for example, the location of the center of the pupil  106  with respect to the first reference location. 
         [0032]    A centroid shift determination module  418  determines the pupil centroid shift based on the pupil centroid. For example only, the centroid shift determination module  418  may determine the pupil centroid shift based on the location of the pupil centroid with respect to the second reference location. A pupil size determination module  422  may determine the pupil size based on the image. For example only, the pupil size may include a radius of the pupil  106 , a diameter of the pupil  106 , or another suitable measurement of the size of the pupil  106 . 
         [0033]    When triggered by the illumination control module  402 , a storage module  426  may store the pupil size and the pupil centroid shift. The storage module  426  may store the pupil centroid shift in a mapping (e.g., a look up table or LUT) by the pupil size. In other words, the storage module  426  may populate a mapping of pupil centroid shifts for the eye indexed by pupil size. In this manner, the mapping may include pupil centroid shifts for various pupil sizes, respectively. 
         [0034]    An exemplary graph of pupil centroid shift as a function of pupil size is presented in the example of  FIG. 5 . While the exemplary graph illustrates a linear relationship between pupil centroid shift and pupil size, the relationship may be non-linear and may take another suitable form. Additionally, while the exemplary graph illustrates a one dimensional relationship between pupil centroid shift (e.g., magnitude) and pupil size, the relationship between pupil centroid shift and pupil size may be multi-dimensional. The example of  FIG. 5  also includes an exemplary illustration of exemplary light intensities  502  and associated exemplary pupil sizes  506  and exemplary pupil centroid shifts  510 , respectively. 
         [0035]    Referring now to  FIG. 6 , a functional block diagram of an exemplary vision treatment system  600  is presented. An image triggering module  602  may selectively trigger an imaging module  606  to take an image. The image triggering module  602  may trigger the imaging module  606  to take images at a predetermined frequency. The predetermined frequency may be set to greater than or equal to twice the treatment frequency of a treatment module  610  that performs the treatment. For example only, the treatment module  610  may include an excimer laser having a treatment frequency of approximately 20 Hz. In such an example, the predetermined frequency may be greater than or equal to 40 Hz. In various implementations, the predetermined frequency may be approximately 200 Hz. 
         [0036]    When triggered, the imaging module  606  takes an image of the eye. For example only, the image may be similar to the example of  FIG. 1 . A pupil size determination module  614  determines the pupil size based on the image. A treatment adjustment module  618  receives the pupil size and a target treatment. In various implementations, the target treatment centroid shift compensation may be generated before the vision correction treatment is performed based on the data from an aberrometer. 
         [0037]    Based on the determined pupil size, the treatment adjustment module  618  retrieves a pupil centroid shift associated with the pupil size. For example only, the treatment adjustment module  618  may retrieve the pupil centroid shift from the storage module  426  based on the pupil size. In various implementations, such as implementations where the pupil centroid shift determination and storage system  400  is implemented independently or with an aberrometer, the contents of the mapping may be made available (e.g., uploaded) to the vision treatment system  600  before the treatment. 
         [0038]    The treatment adjustment module  618  may adjust the target treatment based on the pupil centroid shift and output an adjusted treatment for the eye. For example only, the target treatment may include a center for the target treatment. The treatment adjustment module  618  may adjust the target treatment by moving the center used during the treatment in a direction opposite to the pupil centroid shift. For example only, for a center with coordinates of 0 units in an X-direction and 0 units in a Y-direction (e.g., (0,0)) and for a pupil centroid shift with coordinates of 4 units in the positive X-direction and  3  units in the positive Y-direction (e.g., (4,3)), the treatment adjustment module  618  may adjust the target treatment by moving the center to 4 units in the negative X-direction and 3 units in the negative Y-direction (e.g., (−4, −3)). 
         [0039]    A treatment triggering module  626  selectively triggers the treatment module  610 . The treatment triggering module  626  may trigger the treatment module  610  at the treatment frequency. The treatment frequency may be a predetermined frequency, such approximately 20 Hz. When triggered, the treatment module  610  treats the eye based on the image and the adjusted treatment. In this manner, the pupil centroid shift is accounted for in real-time (actively) during the vision correction treatment. 
         [0040]    Referring now to  FIG. 7 , a flowchart depicting an exemplary method  700  of accounting for pupil centroid shift in real time (active) during a vision correction treatment of an eye is presented. Control may begin at  702  where control may receive a target treatment for the eye. Control may capture an image of the eye at  706 . 
         [0041]    At  710 , control may measure a pupil size based on the image. Control may determine the pupil centroid shift based on the pupil size at  714 . For example only, control may determine the pupil centroid shift from a mapping of pupil centroid shifts for the eye indexed by pupil size populated before the treatment. Control may adjust the target treatment based on the pupil centroid shift at  718 . At  722 , control may treat the eye based on the adjusted treatment, and control may return to  702 . In this manner, control accounts for the possibility (and/or for the variability of the pupil size and the corresponding centroid shift) of variable pupil centroid shift in real time (active) during performance of a vision correction treatment. 
         [0042]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.