Retinal nerve fibre layer thickness measured by Spectralis spectral-domain optical coherence tomography: The Beijing Eye Study

Purpose: The aim of this study was to measure retinal nerve fibre layer thickness (RNFLT) and its associated factors in a population-based setting.

Methods: The population-based Beijing Eye Study 2011 included 3468 individuals. The study participants underwent spectral-domain optical coherence tomography (Spectralis(®) ; Spectralis OCT)-assisted measurement of the RNFLT. For this study, exclusion criteria were glaucoma, pseudoexfoliation, best-corrected visual acuity of >0.5 logMAR, macular diseases, previous ocular surgery and known neurological diseases. The only inclusion criterion was an age of 50+ years.

Results: The inclusion criteria were fulfilled by 2548 participants. Mean RNFLT was 102 ± 11 μm. RNFLT was significantly (p < 0.001) thicker in the temporal inferior sector (153 ± 21 μm) than in the temporal superior sector (138 ± 21 μm), nasal inferior sector (118 ± 24 μm), nasal superior sector (106 ± 21 μm), temporal sector (76 ± 13 μm) and nasal sector (73 ± 15 μm). The mean intereye difference in RNFLT was 4.4 ± 6.0 μm. In multivariate analysis, thicker RNFLT was associated with younger age (p < 0.001), female gender (p < 0.001), urban region (p = 0.003), larger optic disc size (p < 0.001), larger neuroretinal rim area (p < 0.001), hyperopic refractive error (p < 0.001), larger beta zone of parapapillary atrophy (p = 0.008) and thicker subfoveal choroidal thickness (p = 0.02). RNFLT decreased by about 0.2 μm (0.2%) per year of life and by 1 μm (1%) per dioptre of myopia.

Conclusion: Mean RNFLT (measured by Spectralis(®) OCT; 102 ± 11 μm) was associated with younger age, female gender, urban region of habitation, larger optic disc, larger rim, hyperopic refractive error, larger parapapillary beta zone and thicker subfoveal choroidal thickness. Independent of age and refractive error, the RNFL was thickest temporal inferiorly and thinnest temporally and nasally.