Improved Detection of Optical Coherence Tomography (OCT) Structural Abnormality in Glaucoma (GL) with Combined Sectoral Rim and Retinal Nerve Fiber Layer (RNFL) Criteria

Abstract

Purpose : To compare the ability of global and sectoral minimum rim width (MRW) and RNFL thickness (RNFLT) to detect structural abnormality (alone and combined) in 196 GL and 303 Normal eyes.

Methods : Each GL eye (24-2 visual field (VF) pattern standard deviation or glaucoma hemifield test outside normal limits on 2 consecutive tests) and Normal eye underwent a 12° RNFL circle scan and a 24 line optic nerve head (ONH) radial scan with enhanced depth imaging relative to the Fovea-Bruch’s Membrane Opening (FoBMO) axis (Spectralis, Heidelberg Engineering). followed by manual correction of the internal limiting membrane, BMO and outer RNFL segmentations. Global, and sectoral (Garway-Heath (GH) and 30°, Fig. 1) MRW and RNFLT were quantified. OCT abnormality for each parameter was defined as less than the 5^th percentile of the parameter’s Normal eye distribution. OCT abnormality for individual eyes was defined with global, sectoral and combined-parameter criteria that achieved ≥ 95% specificity in the Normal eyes. Criteria achieving ≥ 95% specificity were assessed in all GL eyes and two GL eye subgroups (above and below the median VF mean defect (MD)).

Results : GL eye median MD was -4.95 dB (range, −27.01 to 0.72 dB). Two sectoral combination criteria (1 GH MRW + corresponding GH RNFLT) and (1 30° MRW + any 1 corresponding or adjacent 30° RNFLT) (Fig 1), global RNFLT and global MRW were among the best performing criteria, (99%, 97%, 95% and 95% specificity, and 90%, 91%, 85% and 79% sensitivity, respectively). Among the GL subgroups, these criteria achieved 97%, 97%, 94% and 87% sensitivity for GL eyes with MD worse than -4.95 dB and 83%, 86%, 77% and 71% sensitivity for GL eyes with MD better than -4.95 dB. Among all OCT abnormal GL eyes detected sectorally, abnormal sectors contributing to GL detection occurred most commonly within the inferior temporal sectors (Fig. 2).

Conclusions : Sectoral MRW and RNFLT combination criteria using GH or 30° sectors performed similarly and identified the sectoral location of OCT abnormality with high diagnostic precision. Criteria to integrate OCT sectoral MRW and RNFLT are needed and may enhance the detection and clinical management of eyes with glaucoma once obtained.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.