title: Photorefraction with a catadioptric lens. Improvement on the method of Kaakinen.
abstract: Kaakinen (1979) presented a method of measuring refractive error and ocular alignment by simultaneous photography of corneal and fundus reflexes. As presented, the technique was unable to detect refractive errors of less than 2-3 diopters (Howland 1980; Kaakinen 1979). We demonstrate that the use of a catadioptric lens and a long working distance can improve sensitivity to less than 1.0 D. Refractions of a model eye, an accommodating eye and ametropic eyes indicate that refractive errors greater than 0.75 D are readily detectable. The improvement in sensitivity achieved by the present system is attributable to a reduction of the angle between the flash source and the entrance pupil of the photorefractor.
mesh_terms: D000065:Accommodation, Ocular; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007909:Lenses; D008875:Middle Aged; D010781:Photography; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000175:diagnosis*; D014787:Vision Tests / Q000379:methods*