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Jacqueline Chua, Florian Schwarzhans, Quang Nguyen, Josh Tjunrong Sia, Tien Y Wong, Tin Aung, Georg Fischer, Ching-Yu Cheng, Clemens Vass, Leopold Schmetterer; Compensation of retinal nerve fiber layer thickness as assessed using optical coherence tomography based on anatomical confounders. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1866. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Variations in ocular anatomical parameters are important sources of measurement error of retinal nerve fiber layer (RNFL) thickness. We propose a novel method to compensate the RNFL thickness measures for anatomical confounders.
This is a population-based study of 5221 persons aged 40 and above who received eye examination, including spectral-domain (SD) optical coherence tomography (OCT). Systematic selection process identified 2698 eyes (1076 Chinese, 704 Malays and 918 Indians) with high-quality OCT images from individuals without ocular disease. Optic disc and macular scans were registered to determine the distance between fovea and optic disc centers (fovea distance) and their respective angle (fovea angle). Retinal vessels were segmented in the projection images and used to calculate the circumpapillary retinal vessel density profile. Compensated RNFL thickness was generated based on optic disc (ratio, orientation and area), fovea (distance and angle), retinal vessel density, refractive error and age. Linear regression models were used to investigate the effects of clinical factors on RNFL thickness.
Compensated RNFL was thicker than measured RNFL for all (95μm vs 94μm; P<0.001), Chinese (98μm vs 97μm; P=0.002) and Indians (91μm vs 88μm; P<0.001) whereas it was similar for Malays (96μm; P=0.517). Compensation narrowed the variability in RNFL thickness for all (9.6%; P<0.001), where the effect was greatest for Chinese (10.9%; P<0.001), followed by Malays (6.6%; P=0.075) and then Indians (4.3%; P=0.192). Half of the individuals in the 1% high-risk category (with very thin RNFL) were reclassified into the normal category. Older persons tended to have reduced density of retinal vessels, long-sighted, thin RNFL (all P-trends<0.05). Retinal vessel density was correlated with measured RNFL (β=0.01; P<0.001) but not with compensated RNFL (β=0.01μm; P=0.063). Age become less correlated with compensated RNFL (β=-1.50μm; P=0.004) compared to measured RNFL (β=-3.32μm; P<0.001).
This anatomy-based compensation method narrowed the variability of RNFL measures and reclassified “high-risk” individuals. Age-dependence of RNFL seemed to be largely related to the narrowing retinal vessels rather than loss of retinal ganglion cell axons. Compensated RNFL thickness may improve glaucoma detection, which needs to be confirmed in future studies.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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