INTERFEROMETRIC MEASUREMENT OF CORNEAL THICKNESS WITH MICROMETER PRECISION

The recently developed partial coherence laser Doppler interferometry technique was improved to measure central and peripheral corneal thick ness with high precision. Corneal thickness profiles were measured on 18 eyes of healthy, volunteer subjects. All of these eyes were measura ble at angles (between visual axis and measuring direction) ranging fr om 20 degrees nasal to 25 degrees temporal. At larger angles (up to 35 degrees) only part of the eyes was measurable. The thickness profiles of the 18 corneas have a nearly perfectly parabolic shape within the measured region. The precision (standard deviation) was 1.6 mu m for c entral measurements and decreased somewhat to about 3.5 mu m at measur ing angles in the range of 25 to 30 degrees. No significant interobser ver variability was found on 14 eyes measured by three different obser vers. This study indicates that the new technique is likely, to be sup erior to currently used ultrasound and conventional optical pachymetry techniques, especially for refractive procedures.