Compensation of retinal nerve fibre layer thickness as assessed using optical coherence tomography based on anatomical confounders

Abstract

Background/AimsTo compensate the retinal nerve fibre layer (RNFL) thickness assessed by spectral-domain optical coherence tomography (SD-OCT) for anatomical confounders.MethodsThe Singapore Epidemiology of Eye Diseases is a population-based study, where 2698 eyes (1076 Chinese, 704 Malays and 918 Indians) with high-quality SD-OCT images from individuals without eye diseases were identified. Optic disc and macular cube scans were registered to determine the distance between fovea and optic disc centres (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.ResultsRetinal vessel density reduced significantly with increasing age (1487±214 µm in 40–49, 1458±208 µm in 50–59, 1429±223 µm in 60–69 and 1415±233 µm in ≥70). Compensation reduced the variability of RNFL thickness, 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). Compensation reduced the age-related RNFL decline by 55% in all participants (β=−3.32 µm vs β=−1.50 µm/10 years; p<0.001). Nearly 62% of the individuals who were initially classified as having abnormally thin RNFL (outside the 99% normal limits) were later reclassified as having normal RNFL.ConclusionsRNFL thickness compensated for anatomical parameters reduced the variability of measurements and may improve glaucoma detection, which needs to be confirmed in future studies.

Modelling normal age-related changes in individual retinal layers using location-specific OCT analysis

“…Finally, as OCT is essentially an analysis of reflectance profiles, changes in retinal thickness do not confer information about which specific cellular structures are affected. This limitation was significant in the RNFL, as the main retinal arterioles and venules cause significant variability in thickness measurements 88 and may explain why we, along with another histological study, found the RNFL to be thickest inferiorly 44 as opposed to other studies which found the RNFL to be thickest superiorly [40][41][42][43] . The ambiguity of reflectance profiles in OCT is also evident in analysis of Henle's fibre layer which we kept as part of the ONL segmentation to maintain consistency with other studies and OCT auto-segmentation protocol, despite anatomically being part of the OPL.…”

A Wide-Field Optical Coherence Tomography Normative Database Considering the Fovea-Disc Relationship for Glaucoma Detection

“… 21 Although there was no statistical difference in diagnostic power, it may be more logical to use parameters reflecting the FDD and disc area rather than a constant of 3.4 mm. Additionally, different blood vessel positions may have different effects on each individual 22 , 23 ; however, this was ignored to construct an average normative database.…”

Focal Structure–Function Relationships in Primary Open-Angle Glaucoma Using OCT and OCT-A Measurements

“…In addition, the previous approaches have used standardized definitions of the peripapillary sectors or quadrants for OCT-A analysis and do not account for anatomical individual variations in the relative positions between the optic nerve head and the fovea. These anatomical variations, which have been shown to affect the discriminative ability of peripapillary RNFL measurements in glaucoma, [40][41][42][43] are likely attributed to relative shifts in the positions of the nerve fiber bundles and could affect capillary measurements. An advantage of the focal approach is that we were able to use the actual VF losses at the test locations without averaging over a larger sector.…”