Corneal steep meridian measurement integrated in a Femtosecond Laser Cataract System

Abstract

Purpose : The precision of femtosecond lasers for cataract surgery to place corneal relaxing incisions for the correction of astigmatism is impacted by the manual ink tattoos used to mark the steep meridian. Automatic measurement of steep meridian within a laser cataract system will help to place precise incisions. This study evaluates a CATALYS® system adapted to measure corneal steep meridian and compares the results to two commercial available diagnostic systems.

Methods : In a CATALYS® system, a mask was placed over the internal illumination source to produce two concentric circles of illuminated dots. Prior to a normal laser cataract procedure, images of the dot rings reflected from the patient’s cornea were captured by the onboard video. The ellipticity of the dot ring images was analyzed to determine the orientation of the steep meridian. For reference, the corneal astigmatism was also measured by two commercially available devices: Pentacam corneal topographer and Lenstar optical biometer. Measurements from all three devices were compared for angle and vector difference in measured astigmatism.

Results : The total number of eyes in the study was 39. Of these, 33 were measured with all three devices, and 6 measured with only the CATALYS® system, and Lenstar system. Differences in steep meridian measurement decreased with increasing astigmatism, whether compared between the two commercial devices or either commercial device vs. CATALYS® system. Vector astigmatism differences, which consider both magnitude and angle, were not significantly different between the three devices.
Mean difference in steep meridian angle:
Astigmatism Lenstar-Pentacam Devices Lenstar-Catalys Systems Catalys-Pentacam Systems
0.5D to 1.0D 15^o 20^o 17^o
1.0D to 1.5D 14^o 17^o 14^o
Over 1.5D 4^o 8^o 10^o
Mean difference in vector astigmatism:
Astigmatism Lenstar-Pentacam Devices Lenstar-Catalys Systems Catalys-Pentacam Systems
0.5D to 1.0D 0.36D 0.40D 0.44D
1.0D to 1.5D 0.66D 0.57D 0.65D
Over 1.5D 0.48D 0.47D 0.68D

Conclusions : The CATALYS® system was successfully adapted to measure corneal steep meridian with a precision comparable to commercially available keratometers.
© 2016 Abbott Medical Optics Inc. CATALYS is a trademark owned by or licensed to Abbott Laboratories, its subsidiaries or affiliates. All other trademarks are the intellectual property of their respective owners

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.