Purpose
To classify the appearance of the optic disc seen on fundus photographs of glaucoma suspects and patients with mild glaucoma and to compare these results to those of functional and structural tests.
Methods
One eye of 62 glaucoma patients or suspects was prospectively tested with macular and disc frequency domain optical coherence tomography (fdOCT) cube scans (Topcon Inc, 3D-OCT 2000, Tokyo) and a 10-2 visual field (VF). All eyes had abnormal appearing discs, based upon features below, and a 24-2 MD better than -6.0 dB. Fundus photographs were analyzed by 2 glaucoma specialists and clinical features were classified into one or more of the following 12 categories: Vertical Cup to Disc Ratio (VCDR) >0.6; Disc-Cup Asymmetry >0.2; Small Disc with Significant Cupping; Disc Pit; Focal Rim Thinning; Diffuse Rim Thinning; Disc Hemorrhage; Beta-Zone Peripapillary Atrophy (PPA); Breaks ISNT Rule; Nasal Cupping; Focal Retinal Nerve Fiber Layer (RNFL) Thinning; Diffuse RNFL Thinning. The combined retinal ganglion cell and inner plexiform layers (RGC+) of the OCT macular scans and the RNFL of disc scans were segmented, down-sampled into 64 pixels, and converted to probability plots. The 24-2 VF, 10-2 VF and the RGC+ and RNFL plots were considered normal or abnormal based upon cluster criteria. To minimize false-positives and false negatives, eyes were classified into 3 groups: Normal (all 4 tests in both hemifields within normal limits), Abnormal (both the 24-2 VF and RNFL and/or both the 10-2 and RGC+ were abnormal in at least one hemifield); and Other (the remaining eyes).
Results
The table shows the 8 fundus features observed in ≥3 (4.8%) of the eyes. Overall the VCDR>0.6, Focal Rim Thinning, and ISNT Rule were the most common, occurring in >80% of all eyes. The pattern of results for the Normal (n=14) and Abnormal (n=22) eyes was different (p<0.05, Chi-Sq). The Abnormal group showed a greater percentage of eyes classified as Diffuse Rim Thinning (68 vs. 14%, p=0.002, Fisher’s Exact Test) and PPA (82 vs. 14%, p=0.0001)
Conclusions
Eyes with abnormal structural and functional tests were more likely to have diffuse rim thinning and beta-zone PPA clinically. Focal rim thinning and deviation from the ISNT rule did not differentiate between normal and abnormal eyes.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
627 optic disc •
758 visual fields