Abstract
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 μmfor 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.
Highlights
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
It was closely comparable to the mean value of 250.83 ± 17.04 μm obtained using the Spectralis® SD-OCT in a previous study from the same institution; the subjects were normal Filipinos with no-to-low myopia
The central foveal subfield thickness reference values derived from the mean of a normal cohort for each degree of myopia were as follows: low, 264 ± 24 μm; moderate, 258 ± 17 μm; high, 253 ± 25 μm and pathologic, 218 ± 48 μm
Summary
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. Studies have demonstrated the direct relationship between retinal thickness and increased AL due to thinning of the choroid and sclera and elongation of photoreceptor outer segments.[14] Previous investigations have revealed that the optic disc and the peripapillary atrophy start to enlarge at about an AL of ~26.5 mm and that the prevalence of myopic retinopathy and glaucomatous optic neuropathy steeply increased beyond this value.[13] There are several ocular diseases associated with myopia These diseases may develop in part due to the increased AL and the concurrent structural changes induced within the eye. It is sometimes difficult for Filipino ophthalmologists to decide whether abnormal values on macular and RNFL thickness are reliable
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