AN INFRARED ECCENTRIC PHOTO-OPTOMETER

An objective infrared optometer has been designed, based on the optica l principles of eccentric photorefraction. A CCD camera with an eccent ric infrared light source images the subject's pupil through a Badal o ptometer. The slope of the light distribution across the pupil is cont inuously recorded. Accommodative state is measured by moving the camer a behind the Badal lens until the slope is zero. This position corresp onds to the case where the camera is conjugate with the retina of the observer. In this Badal optometer, the irradiance of light at the pupi l plane, the sensitivity of the photorefractor, and the focal setting of the camera lens remain constant for all positions of the camera fro m the eye. The repeatability of a single measure of refractive state i n a cyclopleged eye was less than 0.05 D. Static accommodative respons es taken from 3 subjects in both closed and open loop conditions provi ded expected stimulus/response measures. The instrument can also be ad apted to measure dynamic accommodation. (C) 1998 Elsevier Science Ltd. All rights reserved.