USOO8197O64B2 (12) United States Patent (10) Patent No.: US 8,197,064 B2 Copland (45) Date of Patent: *Jun. 12, 2012 (54) METHOD AND SYSTEM FOR IMPROVING (56) References Cited ACCURACY IN AUTOREFRACTION MEASUREMENTS BY INCLUDING U.S. PATENT DOCUMENTS MEASUREMENT DISTANCE BETWEEN THE 5,016,643 A 5/1991 Applegate et al. PHOTORECEPTORS AND THE SCATTERING 6,550,917 B1 4/2003 Neal et al. 6,634,752 B2 10/2003 Curatu LOCATION IN AN EYE 6,637.884 B2 10/2003 Martino 7,494.220 B2 * 2/2009 Copland ....................... 351,200 (75) Inventor: Richard Copland, Albuquerque, NM (US) OTHER PUBLICATIONS Cornsweet et al., “Servo-Controlled Infrared Optometer.” Journal of (73) Assignee: AMO Wavefront Sciences LLC., Santa the Optical Society of America, pp. 63-69, 1970, vol. 60 (4). Ana, CA (US) International Search Report for Application No. PCT/US2003/ 20187, mailed on Mar. 12, 2004, 2 pages. Knoll H.A., “Measuring Ametropia with a Gas Laser. A Preliminary (*) Notice: Subject to any disclaimer, the term of this Report.” American Journal of Optometry and Archives of American patent is extended or adjusted under 35 Academy of Optometry, 1966, vol. 43 (7), pp. 415-418. U.S.C. 154(b) by 663 days. Munnerlyn, "An Optical System for an Automatic Eye Refractor'. Optical Engineering, pp. 627-630, 1987, vol. 7 (6). This patent is Subject to a terminal dis Thibos L. N. et al., “The chromatic eye: a new reduced-eye model of claimer. ocular chromatic aberration in humans.” Applied Optics, 1992, 31 (19), 3594-3600. (21) Appl. No.: 12/388,253 * cited by examiner (22) Filed: Feb. 18, 2009 Primary Examiner — Max Hindenburg Assistant Examiner — Jonathan M. Foreman (65) Prior Publication Data (74) Attorney, Agent, or Firm — AMO Wavefront Sciences US 2009/02O7377 A1 Aug. 20, 2009 LLC Related U.S. Application Data (57) ABSTRACT A method and associated system improve accuracy in objec (63) Continuation of application No. 10/640.321, filed on tive refraction measurements by including the measured dis Aug. 14, 2003, now Pat. No. 7,494.220. tance between the photoreceptors of a subject’s eye and the scattering location of light during the objective refraction (51) Int. C. measurements. Chromatic aberrations in the objective mea A6 IB3/00 (2006.01) Surements are also compensated. The distance between the A6 IB3/02 (2006.01) photoreceptors and the scattering location may be determined (52) U.S. C. ........ 351/200; 351/205; 351/222; 351/246; by adjusting a distance between a rotating speckled light 600/558 pattern and an eye until the speckled light pattern appears to (58) Field of Classification Search .................. 600/558; be stationary, or by employing a Scheiner disk. 351/200, 205, 222, 246 See application file for complete search history. 20 Claims, 6 Drawing Sheets OLMATED SLD BEAM t Sy STIES : CCD3 0-7 CRAWFORD : AMP YS)-(E=O. WHITE LIGHT WITH COLOR FILERS : LED D TARGET (FOGGED) a-MOWINGSTAGE--> MODIFIED COASX IRS CCD U.S. Patent Jun. 12, 2012 Sheet 1 of 6 US 8,197,064 B2 COLLIMATED SLD BEAM LED D TARGET L4 4-Sa L5 (FOGGED) III. IRIS CCD U.S. Patent Jun. 12, 2012 Sheet 2 of 6 US 8,197,064 B2 ERROR BETWEEN SR AND COAS 8. O O e SUBJECTIVE REFRACTION SPHERE EQUIV(diopters) FIG. 2 U.S. Patent Jun. 12, 2012 Sheet 3 of 6 US 8,197,064 B2 CAMERA LENS BEING TESTED LASER BEAM GLASS DISC (SPINNING) FIG. 3 U.S. Patent Jun. 12, 2012 Sheet 4 of 6 US 8,197,064 B2 to- SS owpT RETINA CCD COLLIMATED : L3)II SLD BEAM : BS1 N BS2 PBS L2 L1 : L6 BS4 |t CD3E O Y CRAWFORDSTILES i BS5 LAMP I PATIENT ADJUSTMENT LASER : N D (E-Ot(E-ry L7 L9 10 | BS6 : WHITE LIGHT WITH } % COLOR FILTERS | BS7 { 2% LED DTARGET L4 4s L5 ------------------------ (FOGGED) <-MOWING STAGE--> U.S. Patent Jun. 12, 2012 Sheet 5 of 6 US 8,197,064 B2 U.S. Patent Jun. 12, 2012 Sheet 6 of 6 US 8,197,064 B2 LINE OF SIGHT LIGHT US 8, 197,064 B2 1. 2 METHOD AND SYSTEM FOR IMPROVING reduced vision. While a large spacing would not normally ACCURACY IN AUTOREFRACTION result in visual disfunction, if the patient were to develop MEASUREMENTS BY INCLUDING diabetes or glaucoma, the patient could experience an unusu MEASUREMENT DISTANCE BETWEEN THE ally rapid progress in decline of visual function. Such patients PHOTORECEPTORS AND THE SCATTERING 5 would need to be monitored more closely. Similarly, some LOCATION IN AN EYE populations, such as Native Americans, are normally more closely monitored for the onset of diabetes. It may be that data RELATED APPLICATION concerning choroid to photoreceptor spacing would indicate that only a small Subset of those populations are actually in This application is a continuation application of, and 10 need of close monitoring and examination intervals could be claims prior to, U.S. patent application Ser. No. 10/640.321, increased for the remainder of those populations. filed Aug. 14, 2003, which claims priority to PCT application A second application of this measurement of the choroid to no. PCT/US03/020187 file on Jun. 27, 2003, and to U.S. photoreceptor distance would be to improve the accuracy of provisional application No. 60/391,668, filed on Jun. 27. objective refractive measurements that are used to determine 2002, the entire contents of each of which applications are 15 a patient’s eyeglass prescription. Many commercially avail hereby incorporated by reference in their entirety for all pur able autorefractors and wavefront aberrometers reflect light poses as if fully set forth herein. off of the choroid (or the sclera) to provide a light source for Such an automatic measurement. Technicians rather than BACKGROUND AND SUMMARY OF THE highly trained doctors can perform autorefractions, and the INVENTION 2O autorefractions are faster to perform than subjective refrac tions. 1) Field of the Invention Most people are familiar with the process of subjective This invention pertains to the field of subjective measure refraction when an ophthalmologist flips lenses of different ments and characterizations of an eye, and more particularly, strengths in and out of the patients field of view and asks the to measurements and characterizations of an eye with wave- 25 patient if a letter on the wall looks clearer or fuzzier. The front analysis devices. repeatability of subjective refraction is generally considered 2) Description to be about +/-0.25 Diopters. A few practitioners with better FIG. 5 is a diagram of a human eye 500, illustrating the skill and more time to spend with the patient can achieve choroid 510, the fovea layer 520, the lens 530 and the cornea repeatabilities of +/-0.12 diopters. 540. The fovea layer 520 is the area of the retina that contains 30 Meanwhile, the repeatability of autorefraction measure the densest concentration of photoreceptors. ments is better than +/-0.1 Diopters for almost all modern The location of the photoreceptors in the human eye is autorefractors, and that repeatability is much better than that difficult to determine accurately relative to other structures in of subjective refraction the retina. The photoreceptors absorb visible light and they However, according to several review articles, about 20% are transparent to infrared light, making an accurate measure- 35 of patients will have differences between a subjective refrac ment of their location difficult. tion and an autorefraction greater than 0.5 Diopters. Signifi However, there are a number of contexts where an accurate cantly, repeated autorefractions performed on a particular determination of the location of the photoreceptors would patient from the 20% group will consistently give the same prove very beneficial. In particular, as explained in more disagreement with Subjective refraction, so clearly there is detail below, it would be beneficial to provide a system and 40 Some kind of structural difference in those patients eyes rela method for accurately measuring the choroid to photorecep tive to the general population. tor distance in the eye. Eyeglasses prescribed according to Subjective refraction The retina requires a constant supply of blood for it to meet with greater patient satisfaction than those that would be remain healthy, and in fact consumes the greatest amount of prescribed according to autorefractors. Those patients that oxygen (per weight) of any tissue in the human body. Evi- 45 had more than an 0.5 Diopter discrepancy will almost always dence from several sources show that the photoreceptor layer be unhappy with eyeglasses prescribed according to the ranges from 0.1 mm to 0.4 mm from the choroidal blood autorefraction, and happy with the eyeglasses prescribed Supply in normal human eyes. The average distance between according to Subjective refraction. the choroid and the cones in the fovea is 0.2 mm. Although Accordingly, it is standard practice in the evaluation of this distance has not been well studied before, it seems rea- 50 autorefractors to consider subjective refraction to be the “gold sonable to Suspect that in some individuals an abnormally standard since it correlates better with patient visual expe large distance from the nourishing choroid to the photorecep rience than any other measurement. Consequently it is stan tors may predispose them to visual defects resulting from dard practice for ophthalmologists to fine-tune the autorefrac sight degrading diseases such as glaucoma and diabetes. tion values by performing a subjective refraction on the Early identification of abnormal photoreceptor to choroid 55 patient using a phoropter. The result is that autorefractors are spacing may result in improved patient health. only used for screening purposes, or for giving an optometrist The retina is supplied with blood by two means.