ULTRASOUND BIOMICROSCOPIC MORPHOMETRY OF THE ANTERIOR EYE SEGMENT BEFORE AND AFTER ONE DROP OF PILOCARPINE

Purpose: To measure anterior eye segment morphometric data using ultra sound biomicroscopy. This is a new high-frequency, high-resolution ult rasound method enabling the visualisation of the anterior segment of t he living eye with magnification similar to a light microscope. Method s: Thirteen morphometric parameters of the anterior eye segment were m easured before and after the application of one drop of pilocarpine in 10 eyes of 5 persons, using a Zeiss-Humphrey Ultrasound Biomicroscope at a frequency of 50 MHz. In each session, 3 morphometric parameters in the central images (corneal thickness, anterior chamber depth, pupi llary diameter) were measured 4 times, and 10 parameters in the radial images (scleral thickness, angle-opening distance, trabecular-iris an gle, trabecular-ciliary process distance [TCPD], iris thickness 1, 2 a nd 3, iris-ciliary process distance, iris-lens contact distance [ILCD] , iris elevation) were measured on the 3, 6 and 9 o'clock meridians th ree times each. Results: Statistically significant changes were noted in the following parameters: pupillary diameter, iris thickness 1 and 2, and TCPD were decreased, while ILCD was increased after pilocarpine . Wide chamber angles showed a tendency to become narrower and narrow ones to become wider after pilocarpine. Conclusion: One drop of piloca rpine caused significant changes in the anterior eye segment morpholog y. Not only the pupillary diameter decreased but iris thickness and tr abecular-ciliary process distance were also decreased simultaneously. At the same time the contact surface between the lens and iris increas ed significantly. Ultrasound biomicroscopy gives new morphometric imag e information about the anterior eye segment which is not available us ing conventional gonioscopy or ophthalmic echography.