Assessing Glaucomatous Damage on Retinal Nerve Fiber Bundles along the Temporal Raphe using OCT-Reflectance and OCT-Angiography

Abstract

Purpose : To assess retina nerve fiber bundle (RNFB) changes along the temporal raphe in glaucomatous eyes and evaluate the use of the temporal retina to detect subtle glaucomatous damage using OCT-reflectance (OCT-R) and OCT-angiography (OCT-A).

Methods : Eight controls and 7 primary open angle glaucoma patients with either superior or inferior arcuate RNFB defects were imaged using a SDOCT system (Avanti RTVue-XR; Optovue). Ten 3x3mm scans centered at 9° temporal to the fovea were obtained and averaged (PMID:28068370). A superficial OCT-R slab located between the ILM and ILM+15µm was used for RNFB contrast and width measurements (Fig. A&B). Five measurements of RNFB intensity and background intensity were obtained between 1.5-3° and 0-1.5° above and below the temporal raphe, respectively. Michelson contrast of RNFB was then computed. RNFB width was measured on an 80-100µm straightened RNFB segment based on the first derivative of the averaged intensity profiles. OCT-Rs were compared to the respective OCT-As to ensure all measurements were performed on the RNFBs not the blood vessels. Glaucoma patient’s relatively healthy regions and regions with RNFB defect were analyzed separately. Axial length was obtained for ocular magnification correction of each eye.

Results : RNFB contrast was significantly higher in the controls (0.35±0.04) than in glaucoma patient’s region without RNFB defect (0.27±0.06) and region with RNFB defect (0.19±0.08) (Kruskal Wallis test, P=0.002). No significant difference was observed in RNFB width between the controls (30.68±9.47µm), glaucoma patient’s region without RNFB defect (28.60±6.53µm), and region with RNFB defect (24.36±4.73µm) (Kruskal Wallis test, P=0.276).

Conclusions : RNFB contrast and width along the temporal raphe were reduced in glaucoma patients, supporting the use of the temporal retina for assessing glaucomatous damage. Further studies should focus on evaluating the temporal retina as a region for early detection of glaucomatous damage as compared to traditional diagnostic methods.

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