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A. M. Hwang, D. J. Salchow; Effect of Refractive Error on Optical Coherence Tomography of the Retina. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1851. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of refractive error on optical coherence tomography (OCT) measurements of retinal nerve fiber layer (RNFL) thickness, macular thickness and optic disc parameters.
Ten eyes of ten healthy subjects without ocular disease were included (5 females, 5 Caucasian, 5 Asian). Pupils of subjects were dilated with phenylephrine 2.5% eye drops and refractive error determined by autorefraction or manifest refraction. RNFL thickness, macular thickness and optic disc parameters were measured with StratusOCT (software version 4.0.1; Carl Zeiss Meditec Inc., Dublin, CA) using fast scan modes without contact lens (CL), and with soft CL (Proclear Sphere, base curvature 8.6 mm, diameter 14.2 mm, CooperVision Inc., Fairport, NY) of different powers (-10 D, -4 D, +4 D, +10 D), and again without CL. Thus, we assessed the effect of a 20 D change in refractive error on OCT measurements. Statistical analysis was performed using Excel 2003 (Microsoft, Redmond, WA).
Mean age (± standard deviation [SD]) was 30.5 ± 2.2 years. Mean global RNFL thickness without CL was 110.0± 7.4 µm; with +10 D CL it was 108.4 ± 7.5 µm; with -10 D CL it was 111.2 ± 10.3 µm (differences not statistically significant). Mean horizontal cup-to-disc (C:D) ratio without CL was 0.59 ± 0.18. With +10 D CL it was 0.61 ± 0.16, and with -10 D it was 0.60 ± 0.14 (differences not statistically significant). The difference between RNFL thickness measured without CL and with -10 D CL at 5 and 6 o’clock was significantly different (P = 0.0005 and P = 0.001, respectively). A statistically significant difference was also found when comparing RNFL thickness in the inferior quadrant between measurements with +10 D CL and -10 D CL. Mean vertical C:D ratio without CL was 0.53 ± 0.11. With +10 D CL it was 0.54 ± 0.12, and with -10 D it was 0.53 ± 0.11 (differences not statistically significant). Mean foveal thickness was 212.2 ± 26.2 µm and mean total macular volume was 7.18 ± 0.41 mm3 without CL. With +10 D CL it was 210.6 ± 26.5 µm and 7.18 ± 0.44 mm3, and with -10D it was 212.9 ± 25.3 µm and 6.98 ±0.41 mm3 (differences not statistically significant).
RNFL thickness, macular thickness and optic disc parameters, measured with StratusOCT, were not significantly affected by a 20 D change in refractive error induced at the corneal plane. Significant differences in RNFL thickness were found in the inferior quadrant, possibly due to contact lens decentration. We conclude that OCT measurements of the retina and optic disc before and after cataract or refractive surgery, as well as with and without CL may be used for comparison.
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