Factors influencing circumpapillary retinal nerve fibre layer thickness (cRNFLT) in Northern Ireland Cohort Longitudinal Study of Ageing (NICOLA) study

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Purpose: Circumpapillary retinal nerve fibre layer thickness (cRNFLT) is influenced by ocular diseases such as Glaucoma. Demographic and ocular factors including age and refractive error have been shown to influence cRNFLT. To our knowledge the influence of ocular biomechanical properties on cRNFLT as measured by Spectral Domain Optical Coherence Tomography (SD-OCT) has not previously been reported. We report the association between demographic and ocular biomechanical factors and cRNFLT in an adult population based study. Methods: Cross sectional study: The NICOLA study is an ongoing population-based epidemiological study. The ophthalmic assessment includes: SD-OCT cRNFLT scans (Heidelberg Spectralis, Heidelberg Engineering, Germany), colour stereo pairs of the optic disc and Goldmann-correlated intraocular pressure (IOPg), corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH) measured using Ocular Response Analyser (ORA; Reichert, Inc., Depew, NY). Three ORA measurements were taken for each eye and the mean of the measurements with a waveform score >4 were calculated for each eye. Vertical cup-disc ratios (VCDRs) for the first 3001 participants were measured by trained graders who were masked to the cRNFLT measurements. Univariate analyses were conducted then Generalised Estimation Equation (GEE) models were used to enable data from both eyes to be included in multivariable confounder adjusted analysis and the influence of age, sex, IOPg, CH and VCDR were explored. Results: Participants (n=2486) and eyes (n=4375) were included in GEE which demonstrated age (β, -0.139, p<0.001), female gender (β, 2.007, p<0.001), IOPg (β, -0.348, p<0.001) VCDR (β, -1.0817, p<0.001 per 0.1 increase in VCDR) and CH (β, 0.366, p=0.022) were significantly associated with cRNFLT. CRF was not associated with cRNFLT in univariate analysis (r=0.003, p=0.819) and therefore was not entered into the multivariate model. Discussion: Age, gender, IOPg, VCDR and CH were significantly correlated with global cRNFLT in the multivariate analysis. Our study is in agreement with other studies which report significant reduction in cRNFLT with increasing age and male gender.1-3 Our findings are also in agreement with previous studies which report that lower CH is associated with thinner cRNFLT as measured by Heidelberg HRT scanning laser ophthalmoscopy and GDxVCC scanning laser polarimetry.4 Our finding that VCDR and IOPg were significantly associated with cRNFLT in multivariate analysis were not reported in previous studies.2, 3, 5 Study strengths: 1) relatively large sample size, 2) the statistical analysis which utilised available data from both eyes of each participant and accounted for correlations between eyes. Study limitations: 1) cross sectional design which limit the inferences about the effect variables such as age, 2) restricted number of variables explored. Future analysis will include more variables collected from the NICOLA study when data is cleaned and available and longitudinal studies of the effect of age on cRNFLT are recommended. Conclusions: In addition to age, gender and CH we have identified that IOPg and VCDR are significantly associated with cRNFLT when adjusted for other factors. References: 1. Zhang X, Francis BA, Dastiridou A, et al. Longitudinal and cross-sectional analyses of age effects on retinal nerve fiber layer and ganglion cell complex thickness by Fourier-domain OCT. Trans Vis Sci Tech. 2016; 5(2): 1. 2. Zhao L, Wang Y, Chen CX, Xu L, Jonas JB. Retinal nerve fibre layer thickness measured by Spectralis spectral-domain optical coherence tomography: the Beijing Eye Study. Acta Ophthalmol. 2014; 92: e35–e41. 3. Wang YX, Pan Z, Zhao L, You QA, Xu L, Jonas JB. Retinal nerve fiber layer thickness. The Beijing Eye Study 2011. PLoS One. 2013; 8: e66763. 4. Khawaja AP, Chan MPY, Broadway DC, et al. Corneal biomechanical properties and glaucoma-related quantitative traits in the EPIC Norfolk Eye Study. Invest Ophthalmol Vis Sci. 2014; 55: 117–124. 5. Khawaja AP, Chan MPY, Garway-Heath DF, et al. Associations with retinal nerve fiber layer measures in the EPIC-Norfolk Eye Study. Invest Ophthalmol Vis Sci. 2013;54:5028–5034.
Original languageEnglish
Number of pages1
Publication statusPublished - 01 Jun 2017

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