Automated detection of ocular focus.

We characterize objectively the state of focus of the human eye, utilizing a bull's eye photodetector to detect the double-pass blur produced from a point source of light. A point fixation source of light illuminates the eye. Fundus-reflected light is focused by the optical system of the eye onto a bull's eye photodetector [consisting of an annulus (A) and a center (C) of approximately equal active area]. To generate focus curves, C/A is measured with a range of trial lenses in the light path. Three human eyes and a model eye are studied. In the model eye, the focus curve showed a sharp peak with a full width at half maximum (FWHM) of +/-0.25 D. In human eyes, the ratio C/A was >4 at best focus in all cases, with a FWHM of +/-1 D. The optical apparatus detects ocular focus (as opposed to refractive error) in real time. A device that can assess focus rapidly and objectively will make it possible to perform low-cost, mass screening for focusing problems such as may exist in children at risk for amblyopia.

[1]  E. E. Hartmann,et al.  Preschool Vision Screening: Summary of a Task Force Report , 2000, Pediatrics.

[2]  J K Wolfe,et al.  Objective line spread function measurements, Snellen acuity, and LOCS II classification in patients with cataract. , 1993, Optometry and vision science : official publication of the American Academy of Optometry.

[3]  G Westheimer,et al.  Evaluating diffusion of light in the eye by objective means. , 1994, Investigative ophthalmology & visual science.

[4]  P Artal,et al.  Comparison of double-pass estimates of the retinal-image quality obtained with green and near-infrared light. , 1997, Journal of the Optical Society of America. A, Optics, image science, and vision.

[5]  G. V. van Blokland,et al.  Ellipsometry of the human retina in vivo: preservation of polarization. , 1985, Journal of the Optical Society of America. A, Optics and image science.

[6]  G R LaRoche.  Amblyopia: detection, prevention, and rehabilitation , 2001, Current opinion in ophthalmology.

[7]  D. Sliney,et al.  Safety with Lasers and Other Optical Sources , 1980, Springer US.

[8]  J Bescos,et al.  A cinematographic method for the dynamic study of the image formation by the human eye. Microfluctuations of the accommodation , 1981 .

[9]  David G. Hunter,et al.  Determination of ocular defocus using the double-pass blur image of a point source , 1999, Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. N.

[10]  D B Elliott,et al.  Evaluating visual function in cataract. , 1993, Optometry and vision science : official publication of the American Academy of Optometry.

[11]  G. Rubin,et al.  Comparison of acuity, contrast sensitivity, and disability glare before and after cataract surgery. , 1993, Archives of ophthalmology.

[12]  R. Navarro,et al.  Modulation transfer of the human eye as a function of retinal eccentricity. , 1993, Journal of the Optical Society of America. A, Optics and image science.

[13]  Boris I Gramatikov,et al.  Rapid, objective detection of cataract‐induced blur using a bull's eye photodetector , 2002, Journal of cataract and refractive surgery.

[14]  David H. Sliney,et al.  Current Laser Exposure Limits , 1980 .

[15]  P Artal,et al.  Determination of the point-spread function of human eyes using a hybrid optical-digital method. , 1987, Journal of the Optical Society of America. A, Optics and image science.