Accommodation used to determine ultrasound velocity in the human lens.

Intraocular distances can be measured by echography. In this determination the velocity of sound in the various media is assumed to be constant and equal to the velocity found by in vitro measurements. However, interindividual variability causes an inaccurate determination of these distances. We present a method to determine the velocity of ultrasound in the lens "in vivo." For this purpose continuous registrations of the transit times for the anterior chamber, lens, and vitreous were made during accommodation. Regression analysis of the variation of transit times provides the velocity of ultrasound in the lens with an accuracy of about +/- 3 m/s.