Peripapillary Retinal Nerve Fiber Layer Thickness and its Ocular and Systemic Determinants in an Elderly Population: A Population-Based Study.

Purpose: To determine the distribution, ocular, and systemic determinants of peripapillary retinal nerve fiber layer thickness (pRNFLT) using spectral-domain optical coherence tomography (SD-OCT) in an elderly population.

Methods: This report is a part of the Tehran Geriatric Eye Study, a population-based cross-sectional study conducted in Tehran, the capital of Iran. The study population was all residents aged 60 years and above in Tehran. The sampling was performed using a multi-stage stratified random cluster sampling method. All study participants underwent ocular examination (including measurement of visual acuity, objective and subjective refraction, and slit-lamp biomicroscopy), anterior segment imaging using Pentacam HR, and ocular biometry using IOLMaster 500. The OCT imaging was performed for a random subsample (1307 individuals) using Spectralis SD-OCT.

Results: Two thousand two hundred and forty-six eyes of 1189 individuals were analyzed for this report. Of these, 691 (58.1%) were female, and the mean age of the participants was 67.3 ± 5.9 years (60-94 years). The mean overall pRNFLT was 98.6 μ (95% confidence interval [CI]: 98.0-99.3). There was a statistically significant difference in pRNFLT between different quadrants; the highest and lowest mean pRNFLT was related to inferior and temporal quadrants, respectively (P < 0.001). The multiple generalized estimating equation model showed that older age (coefficient: -0.15 [95% CI: -0.24 to -0.06], P = 0.001), diabetes (coefficient: -1.69 [95% CI: -2.82 to -0.55], P = 0.004), and longer axial length (coefficient: -0.52 [95% CI: -0.83 to -0.22], P < 0.001) were significantly associated with a decreased overall pRNFLT. Higher body mass index was significantly related to an increased overall pRNFLT (coefficient: 0.19 [95% CI: 0.07 to 0.30], P = 0.002).

Conclusions: The results of the present study can be used as a reference database for pRNFLT in the elderly population. Considering ocular and systemic determinants of pRNFLT is necessary for correct clinical interpretation of this parameter.