A Simple Subjective Evaluation of Enface OCT Reflectance Images Distinguishes Glaucoma From Healthy Eyes

yesPurpose: We present a subjective approach to detecting glaucomatous defects in enface images and assess its diagnostic performance. We also test the hypothesis that if reflectivity changes precede thickness changes in glaucoma there should be reduced correlation between the modalities in glaucoma compared to controls. Methods: Twenty glaucoma participants and 20 age-matched controls underwent high-resolution OCT scans of one eye. 4 μm-thick enface slabs were constructed through the retina. Enface indices were depths of first gap in visible retinal nerve fiber bundles (RNFBs) and last visible bundle, subjectively evaluated in six sectors of a 3.5 mm circle around the optic disc. Retinal nerve fiber layer thickness (RNFLT) along the same circle was extracted at angles corresponding to enface indices. Between-group differences were tested by linear mixed models. Diagnostic performance was measured by partial receiver operating characteristic area (pAUC). Results: First gap and last visible bundle were closer to the inner limiting membrane in glaucoma eyes (both P < 0.0001). Enface indices showed excellent diagnostic perfor mance (pAUCs 0.63–1.00), similar to RNFLT (pAUCs 0.63–0.95). Correlation between enface and RNFLT parameters was strong in healthy (r = 0.81–0.92) and glaucoma eyes (r = 0.73–0.80). Conclusions: This simple subjective method reliably identifies glaucomatous defects in enface images with diagnostic performance at least as good as existing thickness indices. Thickness and reflectivity were similarly related in healthy and glaucoma eyes, providing no strong evidence of reflectivity loss preceding thinning. Objective analyses may realize further potential of enface OCT images in glaucoma. Translational Relevance: Novel enface OCT indices may aid glaucoma diagnosis

Identifying Glaucomatous Damage to the Macula

SIGNIFICANCE: Measurements of the macula have been increasingly used to diagnose and manage patients with glaucoma. Asymmetry analysis was clinically introduced to assess damage to the macular ganglion cells in patients with glaucoma, but its effectiveness is limited by high normal between-subject variability. PURPOSE: We aimed to reduce the high normal between-subject variability and improve the potential of asymme- try analysis to identify glaucomatous damage to the macula. METHODS: Twenty patients with glaucoma (aged 57 to 85 years) and 30 age-similar control subjects (aged 53 to 89 years) were recruited from a longitudinal glaucoma study. Participants were imaged with the Spectralis OCT using the posterior pole protocol; measurements of the averaged retinal thickness and ganglion cell layer (GCL) thickness were obtained. We established three zones per hemifield within the central ±9°, based on the lowest between-subject variability that we previously found and the course of retinal nerve fiber layer projections. The criteria for flagging abnormality were at least two contiguous zones when P 2.52, P < .01). Asymmetry anal- ysis of retinal and GCL thicknesses flagged 16 and 18 of 20 patients, respectively. CONCLUSIONS: Between-subject variability was reduced in control subjects using the three zones; our criteria identified glaucomatous damage to the macula in most of the patients. We used high-density B-scans to confirm the patterns of the glaucomatous damage we found in this study