Abstract
Abstract: :
Purpose: To evaluate Optical Coherence Tomography (OCT) for diagnosis of early glaucoma. Methods: Early glaucoma was divided into two groups: Early Glaucoma by Visual Field (EGVF) was described as presence of an abnormal automated visual field based on predefined criteria and a mean deviation of – 6.00 dB or better; Early Glaucoma by Disc Only (EGDO) was defined as presence of abnormal disc appearance consistent with glaucoma as judged by two experienced clinicians along with normal achromatic automated visual fields. One eye each from a control group and patients with open-angle glaucoma and visual acuity of 20/30 or better and no other ocular pathology were selected. Established OCT parameters including average nerve fiber layer thickness (NFLT), NFLT in all 4 quadrants, and 12 sectors and 20 other calculated parameters were used for analysis. ANOVA with posthoc Tukey test and linear discrimination analysis (LDA) with ROC curves were used to compare the three groups. P values were adjusted with Bonferroni correction for each set of comparisons. Results: A total of 35 normal eyes, 29 eyes with EGDO and 44 eyes with EGVF were evaluated. Average NFL thickness was 126.8 + 16.8, 103.1 + 26.2, and 86.8 + 28.3 microns in the control, EGDO, and EGVF eyes, respectively (ANOVA, P = 0.000, control group different from both glaucoma groups). Normal eyes were compared to EGDO eyes and a significant difference was observed for the following parameters: NFLT at sectors 3 and 4, and sector 11 (P = 0.001 for all). LDA disclosed NFLT at sector 3 and inferotemporal minus temporal NFLT to be the best discriminating variables. ROC curves derived from LDA showed the area under curve to be 0.834 and 0.960 for EGDO and EGVF groups, respectively (P = 0.00001). With specificity set at 90%, the sensitivity of the OCT for diagnosing glaucoma was 48.6% and 88.6% for EGDO and EGVF groups, respectively. Conclusion: OCT identified early NFL loss in polar regions of the disc in eyes with glaucomatous optic neuropathy and normal achromatic visual fields. Discriminating ability between this group and the control group was fair while performance was significantly better for early perimetric glaucoma.
Keywords: nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • clinical (human) or epidemiologic studies: sys