Diagnosing glaucoma in patients with high myopia is still a challenge despite the rapid develop of optical coherence tomography (OCT) in the past 2 decades. One of the reasons was the different geographic anatomies of the retinal nerve fibre layer (RNFL) among the high myopes and the emmetropes. This often resulted in errors when RNFL thicknesses were analysed. As diagnosis of glaucoma relied on the detection of focal RNFL thinning in OCT, this could lead to wrong diagnosis. This study aimed to compare the distributions of superotemporal and inferotemporal retinal nerve fibre bundles among these 2 groups of population.
Retrospective case-control study. Myopic group comprised subjects with a spherical equivalent of ≤-6D and axial length ≥ 26 mm, whereas non-myopic control group consisted of subjects with a spherical equivalent of 0 ± 0.5D and axial length 24 ± 0.5 mm. Cirumpapillary OCT images were retrieved from all subjects and the distances between the peaks of the 2 retinal nerve fibre bundles was measured.
One-hundred-thirty-four highly myopic eyes from 74 subjects were included in the myopic group and 188 non-myopic eyes from 94 subjects were recruited as control group. The mean inter-peak distance of the myopic group 8.89 ± 1.00 mm and that of the non-myopic group was 6.81 ± 0.61 mm. The mean inter-peak distance was significantly larger in the myopic group (p < 0.0001).
Retinal nerve fibres arranged differently in high myopes with a tendency of more temporally arranged superotemporal and inferotemporal retinal nerve fibre bundles. Direct comparison of RNFL thickness with built-in normative database made by most of the OCT machines might lead to false positive diagnoses of glaucoma in patients with high myopia.