A HAND-HELD PROBE FOR ACOUSTIC COUPLING IN ULTRASONIC INTRAOCULAR DISTANCE MEASUREMENTS OF YOUNG CHILDREN

Abstract

A hand-held, cone-shaped probe standoff made of transparent silicone rubber which maintains a horizontal axis against gravity enables acoustic coupling with the eye by the ultrasonic beam from a partially focused transducer by contact with the cornea of a liquid meniscus at the cone tip. Acceptable intraocular distance measurements are obtained on a non-cycloplegic eye only when approximate coincidence of the transducer axis with the optic axis of the eye occurs. A response from an eye with an undrugged pupil is degraded below acceptable level for an angulation of more than ±2° with, or a translation of greater than ±½ mm from the axis along which maximum amplitude reflections occur. Only second order differences are found in the quality and amplitudes of the reflections obtained by this method and that of the water goggle previously described. The use of a thin membrane as a cap on the standoff is discussed.