Neural contrast sensitivity measurements with a laser interference system for clinical and screening application

Abstract

A He-Ne laser interference device for clinical measurements of the neural contrast sensitivity fraction (CSF) is described. The system uses planoparallel glass plates for the generation of sinusoidal gratings on the retina. Incoherent light from two light-emitting diodes is superimposed for reducing the contrast to a range from 2 X 10-3 to 0.5. The device is coupled with a microcomputer that calculates the contrast sensitivity (CS) and permits control of the system by a dialogue program. The mean CSF for normal observers (95 eyes) is presented, and the data are compared with overall CS values from other authors. Pathologic CSFs of three patients are shown as examples for the clinical application. For screening purposes the CS values for five spatial frequencies are compared with the normal CSF. And loss-of-contrast values are calculated.