Retinal thickness among normal myopic Filipinos using spectral domain optical coherence tomography
Purpose: To determine mean macular and retinal nerve fiber layer (RNFL) thickness of myopic Filipinos using spectral domain optical coherence tomography (SD-OCT) and to evaluate influence of age, gender, and degree of myopia.
Design: Observational clinic-based cohort.
Methods: Participants were divided into two groups: low-moderate myopia [spherical equivalent (SE) -0.50 D to -6.00 D] and high-pathologic myopia (SE < -6.00 D and AL > 26.5 mm). Subgroup analyses between low myopia (refraction < -3.00 D or less) and moderate myopia (> -3.00 D to -6.00 D), and high myopia (> -6.00 D to -8.00 D) and pathologic myopia (more than -8.00 D) were done. Macular and RNFL thickness were measured by a SD-OCT and axial length (AL) with non-contact biometry.
Results: Of 156 eyes, 88/156 (56%) had low-moderate myopia, 68/156 (44%) had high-pathologic myopia. There were 67/156 (43%) male and 89/156 (57%) female subjects. Mean central foveal subfield thickness measurements were 264 ± 24 μm for low myopia, 258 ± 17 μm for moderate myopia, 253 ± 25 μm for high myopia, and 218 ± 48 μm for pathologic myopia. Mean RNFL thickness measurements were 105.62 ± 3.89 μm
for low myopia, 97.6 ± 2.45 μm for moderate myopia, 85.9 ± 3.87 μm for high myopia, and 75.14 ± 3.89 μm for pathologic myopia. Average SE (p < 0.0001) decreased while AL (p < 0.0001) increased with more myopia. Myopia and age significantly affected macular and RNFL thickness parameters except for the following where only the degree of myopia was a significant factor: central foveal, temporal parafoveal, nasal perifoveal, inferior and nasal RNFL thicknesses.
Conclusion: Retinal SD-OCT thickness measurements decreased with increasing level of myopia and age. Central foveal, temporal parafoveal, nasal perifoveal, inferior and nasal RNFL thicknesses may be more appropriate SD-OCT parameters among myopic Filipino patients to monitor for glaucoma since they may be less influenced by age.