Objective: To compare the rates of retinal nerve fibre layer (RNFL) thinning in subgroups of patients with glaucoma based on spherical equivalent (SE).

Methods: In this retrospective study, patients were classified into three subgroups, namely, non-myopic glaucoma (NMG, >0 dioptres (D)), mild-to-moderate glaucoma (MMG, 0 to -6 D) and highly myopic glaucoma (HMG,<-6 D), according to their SE. Linear mixed effects models were used to evaluate the rate of change of RNFL thickness determined by spectral domain optical coherence tomography, adjusting for potentially confounding factors.

Results: Among 231 glaucomatous eyes from 231 patients (mean followed up 4.5 years), 105 (45.5%) were classified as NMG, 100 (43.2%) as MMG and 26 (11.3%) as HMG. Baseline visual field mean deviation did not differ among the three subgroups (-4.15 vs -5.44 dB vs -4.38 dB, p=0.185). Thinning rate of average RNFL did not differ among the three subgroups (-0.58, -0.52 and -0.54 μm/year, p=0.931). However, RNFL thinning rate at temporal quadrant (-0.85 vs -0.23 μm/year, p=0.046) and eight o'clock sector was greater in the HMG than in the NMG subgroups (-1.72 vs -0.35 μm/year, p=0.003), while that of one o'clock sector was greater in the NMG than in the HMG subgroups (-0.93 vs 0.45 μm/year, p=0.009).

Conclusions: Overall rate of RNFL thinning was not different among the glaucoma subgroups based on refractive error. However, sectoral RNFL thinning showed significant difference.