Thinner retinal nerve fibre layer in healthy myopic eyes with thinner central corneal thickness.

Abstract

Thinner central corneal thickness (CCT) is a risk factor for conversion from ocular hypertension to glaucoma and for disease progression. However, little is known about the relationship between CCT and characteristics of the optic nerve and the retinal nerve fibre layer (RNFL) in non-glaucomatous eyes. Because myopic eyes may pose diagnostic challenges when assessed for glaucoma, characterising the relationship between CCT and RNFL in these eyes is clinically relevant. Our aim was to investigate the relationship between CCT and RNFL thickness in non-glaucomatous eyes with small/moderate myopia. This was a single-centre, observational, prospective, assessor-masked study. Consecutive eligible patients (myopia ≤ - 6.0 dioptres, astigmatism ≤ 2.0 dioptres) without other ocular or neurodegenerative diseases were included. Based on their CCT, the participants were allocated to group 1 (CCT > 555 μm) or group 2 (CCT < 555 μm). Peripapillary RNFL measurements were performed by a masked observer using the Spectralis OCT platform. Sixty eyes were included in group 1 and 63 in group 2. The CCT in the two groups was significantly different (584.27 ± 22.8 μm vs 522.23 ± 20.03 μm, p = 0.0001). There were no other significant differences in the groups in terms of age, refraction, or intraocular pressure. The peripapillary RNFL thickness was higher (all p < 0.005) in group 1 at several sectors: superior-temporal, inferior-temporal, inferior-nasal, and average. A significant positive correlation between CCT and average RNFL thickness was found for the whole population (r = 0.31, p = 0.0001). Otherwise, healthy myopes with thinner CCT have thinner RNFL compared with participants of similar age and refraction with thicker CCT.