Abstract
Abstract: :
Purpose: To compare RNFL thickness measurements pre- and post-LASIK using fixed and variable corneal compensation scanning laser polarimetry (GDx, GDxVCC; both Laser Diagnostic Technologies, San Diego, CA), and Optical Coherence Tomography (OCT3, Carl Zeiss-Meditec, Dublin, CA) which measures RNFL thickness independent of ocular (retinal and corneal) birefringence. Methods: RNFL thickness was measured pre- and approximately 3 months post-LASIK in one eye each of nine (9) patients using GDx, GDx VCC and OCT 3. Ten (10) normal controls also were tested at baseline and approximately 3 months later. For all subjects, GDx VCC corneal compensation was reset in follow-up scans. Paired t-tests were used to evaluate change from baseline RNFL thickness measurements. Results: At baseline, mean (+ SD) RNFL thickness for GDx, GDx-VCC and OCT3 were 70.4 ± 17.2 µm, 54.0 ± 5.6 µm, and 96.0 ± 17.0 µm, respectively. No significant differences in baseline measurements between LASIK and control eyes were found. In both groups, no significant changes in GDx VCC and OCT 3 RNFL thickness measurements between baseline and follow-up were noted on the overall and in the superior and inferior quadrant (mean change was < 6 µm for each instrument). In the control group there also was no significant change in GDx RNFL measurements between baseline and follow-up. In LASIK patients, significant reductions in GDx average RNFL thickness (mean ± SD change –12.6 µm ± 10.6 µm), superior quadrant (mean ± SD change –12.9 µm ± 9.5 µm) inferior quadrant (mean ± SD change –18.3 µm ± 12.6 µm) were found (all p < .007). Conclusions: At baseline, mean (+ SD) RNFL thickness for GDx, GDx-VCC and OCT3 were 70.4 ± 17.2 µm, 54.0 ± 5.6 µm, and 96.0 ± 17.0 µm, respectively. No significant differences in baseline measurements between LASIK and control eyes were found. In both groups, no significant changes in GDx VCC and OCT 3 RNFL thickness measurements between baseline and follow-up were noted on the overall and in the superior and inferior quadrant (mean change was < 6 µm for each instrument). In the control group there also was no significant change in GDx RNFL measurements between baseline and follow-up. In LASIK patients, significant reductions in GDx average RNFL thickness (mean ± SD change –12.6 µm ± 10.6 µm), superior quadrant (mean ± SD change –12.9 µm ± 9.5 µm) inferior quadrant (mean ± SD change –18.3 µm ± 12.6 µm) were found (all p < .007).
Keywords: imaging/image analysis: clinical • nerve fiber layer • refractive surgery: LASIK