Effect of Contact Lens Power on Optical Coherence Tomography of the Retinal Nerve Fiber Layer

PURPOSE: To study the effect of contact lens (CL) power on retinal nerve fiber layer (RNFL) thickness measurements using optical coherence tomography (OCT). METHODS: Cross-sectional study on 15 healthy subjects. Peripapillary RNFL thickness was measured using time-domain OCT without CL and with CL of different powers (+4 D, +10, -4D, and -10 D), and again without CL. RNFL thickness measurements were compared statistically. RESULTS: Age of study subjects was 30.5 ± 3.2 (mean ± SD) years. Global RNFL thickness measurements showed good repeatability (average without CL was 107 ± 9.3 μm for the first measurement, and 107.4 ± 7.4 μm for the second [P = 0.8]). There was no significant effect of CL power on global RNFL thickness, although more variability was observed with the -10 D CL. When analyzing individual clock-hour segments, only differences in the 6 o'clock hour segment were statistically significant (between -10 D CL [155.9 ± 22.4 μm] and without CL [143.5 ± 19.3 μm], as well as between -10 D and +4 D CL [138.9 ± 19.9 μm], with P < 0.001). When analyzed for individual quadrants, differences in the inferior quadrant were significant between measurements with -10 D CL and all other CLs. CONCLUSIONS: Refractive error changes at the corneal plane do not significantly affect RNFL thickness measurements using OCT; caution is warranted in inferior segments, where variations may occur. These results may be applicable to RNFL thickness measurements before and after cataract or refractive surgery.