Infrared photoretinoscope

Abstract

A modification of the technique of photoretinoscopy is presented which allows measurement of the refractive state of the eye in noncooperative subjects and in very small eyes. Infrared light provided by high-output infrared LEDs permits measurement at large pupil sizes and thereby better resolution. Arrangement of the IR LEDs at different eccentricities from the optical axis of the video camera markedly increases the range of measurement. The current sensitivity for a measurement distance of 1.5 m in a human eye is ± 0.3 diopter or better over a range of ±5 diopters. Higher amounts of defocus can be better determined at shorter distances.