Source: https://patents.google.com/patent/EP1383429A1/en
Timestamp: 2019-10-20 03:49:52
Document Index: 148203629

Matched Legal Cases: ['art 52', 'art 54', 'art 52', 'art 52', 'art 54', 'art 54', 'art 54']

EP1383429A1 - Iris pattern recognition and alignment - Google Patents
EP1383429A1
EP1383429A1 EP01274188A EP01274188A EP1383429A1 EP 1383429 A1 EP1383429 A1 EP 1383429A1 EP 01274188 A EP01274188 A EP 01274188A EP 01274188 A EP01274188 A EP 01274188A EP 1383429 A1 EP1383429 A1 EP 1383429A1
EP01274188A
EP1383429B1 (en
2001-04-27 Priority to US286954P priority
2001-05-10 Application filed by Bausch and Lomb Inc filed Critical Bausch and Lomb Inc
2004-01-28 Publication of EP1383429A1 publication Critical patent/EP1383429A1/en
2008-09-17 Publication of EP1383429B1 publication Critical patent/EP1383429B1/en
238000003909 pattern recognition Methods 0 abstract claims description title 13
This application is related to PCT EP00/10373. Field of the Invention
The popularity of photorefractive surgery for the correction or enhancement of vision continues to rise. Techniques such as photorefractive keratotomy (PRK), laser in situ keratomileusis (LASIK), laser epithelial keratomileusis (LASEK) and variations thereof are now commonly used to correct the effects of nearsightedness (myopia), farsightnesses (hyperopia), and astigmatism, in addition to more traditional retinal surgery and other ocular surgical procedures. These vision defects are typically treated by laser ablating the cornea to steepen or flatten it according to its deviation from a geometry that is expected provide normal vision. A topography device such as, e.g., an
Orbscan® corneal topographer (Bausch & Lomb/Orbtek, Salt Lake City, Utah) is
routinely used to acquire the diagnostic information about the shape and other characteristics of the cornea. A surgeon can then use a laser programmed with this topographic information to appropriately ablate the corneal surface. Basically, hyperopia and myopia, and astigmatism, are known as lower order aberrations referred to as defocus and cylinder, respectively. It is well known that higher order aberrations in addition to lower order aberrations degrade vision quality. Typical higher order aberrations include spherical aberration, coma, and compound astigmatisms. It is possible to measure these higher order aberrations with wavefront measuring devices such as disclosed in Williams U.S. Patent No. 5,777,719 (incorporated herein by reference in its entirety), which describes an aberrometer instrument incorporating a Hartmann-Shack wavefront sensor to quantify higher order aberrations in the eye. The diagnostic measurement of higher order aberrations has lead to the ongoing development of systems and methods for customized ablation of the cornea and lenses used in or on the eye. The goal of customized ablation is to provide ever increasing visual quality in terms of acuity and contrast sensitivity (sometimes referred to as supernormal vision), as well as consistent image quality.
One technique being developed to address these issues is referred to as iris pattern recognition. Rotation of the eye, for example, can sometimes be measured by identifying iris patterns using markers (artificial) or landmarks (natural). Since each person's iris is as unique as their fingerprints, it is proposed that various iris landmarks can be used to identify changing eye orientation. The reader is referred to the web site addresses: http://www.iriscan.com and http://schorlab.berkeley.edu for further information about iris pattern identification and eye movement. Notwithstanding that iris landmarks remain constant over the lifetime of the individual, it has been found that often the change in pupil size between diagnostic evaluation (dilated) and the treatment phase (constricted) is sufficient to deform or otherwise obscure the landmark, making it undetectable by conventional iris recognition software between diagnostic evaluation and treatment. Since it is highly desirable to be able to align the photoablative treatment of the cornea or other eye sites with the diagnostic measurement reference upon which it is based, there is a recognized need for methods and apparatus to acquire and maintain accurate alignment. A solution is proposed in applicant's co-pending patent application
PCT/EP00710373 which is incorporated herein in its entirety. That application discusses associating an artificially applied marker with diagnostic stage and therapeutic stage iris images in order to align these images at treatment. Thermal and dye based marks, for example, are suggested as artificial markers. It is appreciated, however, that patient discomfort, efficiency and accuracy are some disadvantages of current iris recognition and alignment means.
Accordingly, a need exists for devices, systems and methods to accurately account for the eye movement occurring between the diagnostic evaluation and treatment stages of laser eye surgery. The invention, while not limited as such, will be discussed in relation to laser vision correction such as LASIK, for example. SUMMARY OF THE INVENTION
The invention is directed to apparatus and methods for aligning diagnostic and treatment images of a patient's eye in the absence of consistent parameters of the eye at the diagnostic evaluation stage and the treatment stage, in order to obtain improved results from laser vision correction surgery.
These and other objects of the present invention will become more readily apparent from the detailed description to follow. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art based upon the description and drawings herein and the appended claims. Description of the Drawings
Figure 1 is an illustration of two iris images having a constricted pupil and a dilated pupil, respectively, showing the change in form, position and size of naturally occurring landmarks at the two pupil diameter extremes;
Figure 2 schematically shows three sequential iris images having varying pupil diameters and the respective iris landmarks;
Figure 3 schematically illustrates pupil center displacement with respect to a limbal reference as a function of different pupil sizes.
Figure 4 is a schematic illustration of a device according to an embodiment of the invention;
Figure 5 is a schematic illustration of a system according to an embodiment of the invention.
While the present invention is described with reference to illustrative embodiments for particular applications, it should be understood that the present invention is not so limited. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention will be of significant utility without undue experimentation.
An embodiment of the invention is described below in accordance with Figures 1 and 2. Systems and devices are known which use iris pattern recognition for identifying eye structures and for aligning diagnostic and therapeutic images for eye surgery. For example, PCT/EP00/10373 discusses systems and methods for alignment and photorefractive treatment of an eye in which a diagnostic iris image identified with artificial markers is obtained by a camera system along with a refractive diagnostic measurement. A computer system linked to the laser treatment system then uses this iris image information to develop and align the photorefractive treatment.
Figure 1 schematically shows two sequential iris images 10', 10. Image 10 shows an iris area 12, a constricted pupil 14 and typical iris landmarks 16. For the purpose of the description of the invention, the term "constricted pupil" refers to a substantially small pupil size caused by bright light conditions, e.g., eye tracker and fixation light sources along with other environmental conditions present during the treatment phase of laser eye surgery that cause the pupil to constrict. The term constricted pupil, therefore, is not intended to merely describe the smallest possible pupil size that can be induced in a patient's eye, but to describe the smallest working pupil size in accordance with the invention. Iris image 10' shows the same iris 12', however the pupil 14' is dilated and the iris landmarks 16' are shown somewhat obscured due to the dilation of the pupil with respect to iris image 10. The dilated pupil 14', for the purpose of the description of the invention, is due to low light conditions typically associated with diagnostic measurement of the eye, for example, when a wavefront measuring device such as a Zywave™ (Bausch & Lomb/Technolas, Munich, Germany) wavefront measuring device
or an Orbscan II® (Orbtek, Salt Lake City, Utah) corneal topographer is used to obtain wavefront aberration information. Thus, the term "dilated pupil" is not intended to refer merely to a maximally dilated pupil that is chemically or artificially induced, but rather to a dark adapted pupil, which is the largest working pupil size associated with this invention. The iris images 10, 10' in Figure 1 are intended to illustrate the changes in form, position and size of naturally occurring landmarks 16, 16' when pupil size changes dramatically (e.g., from dilated to constricted). Under these circumstances, current iris pattern recognition technology has fallen short of being able to match landmark 16 in the constricted pupil condition with landmark 16' in the dilated pupil condition. Therefore, artificial markers on the eye have been used as in tracking points.
According to the invention, an improvement is described with reference to Figure 2 as follows. In the diagnostic phase of laser vision surgery, a patient's wavefront aberration is measured. Wavefront measurements are typically centered about the patient's visual axis or about the center of the patient's dilated pupil. It is advantageous to measure the wavefront aberration over the dilated pupil because certain higher order aberrations manifest their vision compromising effects when the pupil is dark adapted (e.g., night time vision). Iris image 10' schematically shows the patient's iris image during diagnostic measurement, having a dilated pupil 14' and iris landmarks 16'. By controlling the visible illumination to either the patient's eye undergoing examination or the patient's other eye (not undergoing examination), preferably via a variable illumination fixation target in the diagnostic evaluation device, the pupil diameter of the eye being examined can be controlled. With reference to Figure 2, a diagnostic iris image 10' is obtained by a diagnostic iris image capture device with the image 10' corresponding to the pupil diameter during the diagnostic evaluation. The visible illumination level is increased, causing a corresponding decrease in pupil diameter illustrated by 14" in iris image 10". Iris landmarks 16" are also visible having undergone a lesser change than shown in images 10', 10 of Figure 1. As the illumination level is further increased, another diagnostic iris image 10 is obtained which shows a constricted pupil 14 and iris landmarks 16 which, again, have undergone a small and detectable change from landmarks 16" in iris image 10". In this case, the pupil diameter 14 shown in diagnostic iris image 10 will substantially correspond to the pupil diameter of a treatment iris image obtained by a treatment iris image capture device during the treatment phase of the laser vision correction surgery. Diagnostic iris image processing hardware and software can now track the changes in the sequential set of iris images 10',
10", 10 by tracking the landmark indicia so that the iris image 10' associated with the dilated diagnostic pupil 14' can be aligned with the iris image 10 associated with the constricted diagnostic pupil 14. Iris image processing hardware and software connected to a treatment part of the laser system is now used to align a treatment iris image, substantially represented by iris image 10 in Figure 2, with the exported diagnostic iris image 10, allowing the laser ablation treatment pattern directed to the constricted treatment pupil to be accurately aligned with respect to the diagnostic iris image associated with the dilated diagnostic pupil. An advantage of this embodiment wherein the diagnostic iris images are sorted and aligned by the diagnostic stage processing results in the limited data transfer of a single image from the diagnostic phase to the treatment phase.
Since it is known that the rotational orientation of an eye changes when a patient moves from a sitting position to a supine position, the alignment method according to the invention provides appropriate information for rotating the laser ablation treatment pattern to correspond to the cyclo-rotation of the eye. A diagnostic measurement of the patient's eye in the dilated pupil condition is obtained in addition to the diagnostic iris images with the dilated through constricted pupil. As such, the image acquiring apparatus and the diagnostic measurement device may be separate devices, or, these functions may be integrated into a single device. Ultimately a diagnostic measurement will be used by the treatment laser system to calculate the appropriate ablation profile for vision correction. Therefore, it is preferable that the dilated diagnostic measurement be simultaneously associated with the dilated pupil diagnostic iris image. The diagnostic measurement itself will advantageously include the patient's wavefront aberration information which can be directly obtained by a variety of wavefront sensor instruments. One such device is the Zywave wavefront analyzer (Bausch & Lomb/Technolas) which incorporates a Hartmann-Shack wavefront sensor. Other types of devices such as
elevation based topographers with ray trace capability such as, e.g., Orbscan II®corneal
topography device (Bausch & Lomb/Orbtek, Salt Lake City, Utah) can provide measurement data from which wavefront aberration information can be derived. The diagnostic measurement also preferably includes a measure of the astigmatism. In an aspect of this embodiment, the entire plurality of diagnostic iris images can be exported to the treatment stage processor where the diagnostic iris images can be sorted and appropriately aligned for correlation with the treatment iris image. This aspect would allow tracking and alignment of the treatment iris image in real time with a corresponding diagnostic iris image during the course of surgery. Due to the volume of information being transported between the diagnostic image processor and the treatment image processor, considerably more processing power may be required than for an alternative aspect in which the sorting and alignment of the dilated pupil and constricted pupil iris images is performed by a diagnostic image processor which then exports the aligned constricted pupil image to the treatment image processor for correlation and alignment with the treatment iris image. In this aspect, the computing power requirement is reduced at the expense of a static image comparison with the treatment iris image. A variety of factors will ultimately determine which aspect is preferred by the practitioner.
While the above alignment method provides an improved iris pattern recognition method for rotational adjustment of a laser treatment pattern, it will be appreciated that it is advantageous to translationally adjust the laser treatment pattern due to the translational shift that occurs in pupil center locations between a dilated pupil and a constricted pupil. With reference to Figure 3, a diagnostic image 30' of the patient's eye having a dilated pupil 34' is obtained. A center location 36' of the dilated pupil 34' is determined with respect to an illumination independent eye landmark, preferably an edge of the limbus 32 of the patient's eye. Algorithms and mathematical means for calculating a center location of a pupil with respect to a radial reference point are well known by persons skilled in the art and require no explanation for carrying out the invention. A selected amount of visible illumination is directed to the eye to constrict the pupil as shown in eye image 30 by pupil 34. The center location 36 of the constricted pupil 34 is determined with respect to the eye landmark 32 which is the same as eye landmark 32 in image 30'. The limbal edge provides an advantageous reference point because the limbus is substantially unaffected by changes in pupil size. The vector displacement of the dilated pupil center 36' and the constricted pupil center 36 is determined by techniques well known to those skilled in the art. This vector displacement is then used to adjust the position of a calculated laser ablation treatment profile to be applied to the eye having a constricted pupil based upon diagnostic wavefront information obtained from the diagnostic image of the eye having a dilated pupil. It is advantageous to obtain the diagnostic images of the patient's eye and the measurement of the displacement of the center location of the pupil in infra red light so that pupil size does not change during this data acquisition. Once the vector displacement of the pupil centers is determined, this information can be saved in a treatment file of a controller of a treatment laser for use at an appropriate time.
With reference to Figure 4, an improved diagnostic device 40 is described. In a preferred embodiment, device 40 is an aberrometer such as that described in Williams id, for obtaining a wavefront aberration measurement of a patient's eye 42. An iris 41 and a pupil 43 of the eye 42 are also shown. The aberrometer 40 typically contains an IR camera 44 for obtaining diagnostic images such as those schematically shown in Figures 1 and 2, a wavefront sensor and associated optics and electronics schematically represented by numeral 46 in Figure 4, and a fixed illumination level fixation target 48 used for alignment purposes as well understood by those skilled in the art. According to the invention, the improvement comprises replacing fixed illumination fixation target 48 with a variably controllable visible illumination fixation target so that the diameter of the pupil 43 of the patient's eye can be changed to obtain the diagnostic iris images as described herein above. In an alternative aspect of this embodiment illustrated by the dotted line inserts 49 in Figure 4, the controllable visible illumination source can be externally associated with the device 40 as represented by controllable visible illumination sources 49.
A system embodiment according to the invention is described with respect to Figure 5. The system 50 is a diagnostic and therapeutic system for laser eye surgery that includes a diagnostic part 52 and a laser treatment part 54. The diagnostic part 52 includes a diagnostic instrument 40 as described with respect to Figure 4 and a diagnostic processor 56 that is programmed to sort, correlate and align the diagnostic iris images as represented in 58. An ultimately aligned constricted pupil diagnostic iris image (as described herein above) is exported from diagnostic part 52 as illustrated by reference 59 via any variety of well-known image data transfer means including land based and wireless communications, computer storage media such as disk or CD, via the
Internet or other networks, etc., to laser treatment part 54. Laser treatment part 54 includes a treatment iris image capture device 64 for obtaining the treatment iris image having a constricted pupil of eye 42', a treatment laser 62 and other components such as an eye tracker (not shown). In an alternative aspect of this embodiment, the entire plurality of diagnostic iris images as represented at 58 is exported to treatment part 54 where processing hardware and software represented by processor 66 sorts and correlates the diagnostic iris images and provides the appropriate alignment between the constricted pupil treatment image and the corresponding constricted pupil diagnostic iris image.
Processor 66 may also control the calculated laser ablation pattern in response to the iris pattern recognition alignment.
1. A method for aligning a diagnostic iris image of a patient's eye having a dilated pupil with a treatment iris image of the eye having a constricted pupil, via an iris pattern recognition technique, wherein an iris recognition landmark in the dilated pupil diagnostic image is not directly identifiable with the corresponding iris recognition landmark in the constricted pupil treatment iris image, characterized by: visibly illuminating the patient's eye with a plurality of selected levels of visible illumination to effect a corresponding plurality of different pupil sizes ranging from a constricted pupil diameter to a dilated pupil diameter; respectively obtaining a sequential plurality of diagnostic iris images each of which has an indicia of the iris recognition landmark; correlating the indicia of the iris recognition landmark in each sequential diagnostic iris image such that the iris recognition landmark in the constricted pupil diagnostic iris image is identifiable with the iris recognition landmark in the dilated pupil diagnostic iris image; making a diagnostic measurement of the patient's eye and the associated diagnostic image when the pupil is dilated; obtaining a treatment iris image of the patient's eye having a constricted pupil; aligning the constricted diagnostic iris image with the constricted pupil treatment iris image.
8. The method of claim 1 to 7, further characterized by determining an illumination independent reference landmark on the eye; calculating a center position of the pupil with respect to the reference landmark associated with the dilated pupil diagnostic iris image; calculating a center position of the pupil with respect to the reference landmark associated with the constricted pupil diagnostic iris image; determining a vector displacement value for the constricted pupil center and the dilated pupil center; adjusting the laser treatment to be performed on the constricted pupil eye with respect to the vector displacement of the dilated pupil center.
11. In a diagnostic and therapeutic system for laser eye surgery wherein a diagnostic image of a patient's eye that is obtained by a diagnostic image capture is aligned with a treatment image of the patient's eye that is obtained by a treatment image capture device that is associated with a treatment laser system, via an iris pattern recognition technique, the improvement characterized by: an illumination control device for controlling a visible illumination level on one of the patient's eye being examined and the patient's other eye (not being examined) wherein the visible illumination level acts as a control for the pupil diameter of the examined eye; a sequential plurality of diagnostic iris images each including a different pupil diameter ranging between a dilated pupil size and a constricted pupil size corresponding to the controlled visible illumination level, wherein at least an indicia of an iris recognition landmark is identifiable in each sequential diagnostic iris image even though the corresponding iris recognition landmark is not identifiable between the constricted diagnostic pupil image and the dilated diagnostic pupil image; an eye diagnostic measuring device for obtaining a diagnostic measurement of the patient's eye associated with the dilated diagnostic pupil image, cooperatively associated with the illumination control device and the diagnostic image capture device; means for exporting at least one of the diagnostic iris images to the laser treatment system; and means for aligning the dilated pupil diagnostic iris image with the constricted pupil diagnostic iris image, and further for aligning the aligned constricted pupil diagnostic iris image with the treatment iris image having a constricted pupil of a size generally corresponding to the diagnostic image constricted pupil size.
13. In a diagnostic and therapeutic system for laser eye surgery wherein a diagnostic image of a patient's eye that is obtained by a diagnostic image capture device that is also adapted to make a diagnostic measurement of the patient's eye, is aligned with a treatment image of the patient's eye that is obtained by a treatment image capture device which is associated with a treatment laser system, via an iris pattern recognition technique, the improvement characterized by: an illumination control device for controlling a visible illumination level on one of the patient's eye being examined and the patient's other eye (not being examined) wherein the visible illumination level acts as a control for the pupil diameter of the examined eye; a sequential plurality of diagnostic iris images each including a different pupil diameter ranging between a dilated pupil size and a constricted pupil size corresponding to the controlled visible illumination level, obtained by the diagnostic image capture device, wherein an iris recognition landmark is identifiable in each sequential diagnostic iris image even though the corresponding iris recognition landmark is not identifiable between the constricted diagnostic pupil image and the dilated diagnostic pupil image; means for exporting at least one of the diagnostic iris images to the laser treatment system; means for aligning the dilated pupil diagnostic iris image, associated with a diagnostic measurement image, with the constricted pupil diagnostic iris image; and means for aligning the aligned constricted pupil diagnostic iris image with the treatment iris image having a constricted pupil of a size generally corresponding to the diagnostic image constricted pupil size.
24. The device of claim 22, wherein said device is an abercometer.
EP01274188A 2001-04-27 2001-05-10 Iris pattern recognition and alignment Active EP1383429B1 (en)
US286954P 2001-04-27
EP1383429A1 true EP1383429A1 (en) 2004-01-28
EP1383429B1 EP1383429B1 (en) 2008-09-17
EP01274188A Active EP1383429B1 (en) 2001-04-27 2001-05-10 Iris pattern recognition and alignment
See references of WO02087442A1 *
JP5882967B2 (en) 2016-03-09 How to align toric lenses using preoperative images
2004-07-09 EL Fr: translation of claims filed
2004-09-17 EM Fr: revised translation of claims filed
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