Retinal Nerve Fiber Layer Evaluation in Open-Angle Glaucoma

Abstract

Purpose: To determine the optimum criteria for optical coherence tomography (OCT) to discriminate best between healthy and glaucomatous eyes. Design: A prospective cross-sectional study. Methods: In total, 164 eyes selected from clinical practice were included in this study. These were classified into 98 healthy and 66 glaucomatous eyes, depending on the intraocular pressure, appearance of the optic disc and standard automated perimetry results. Only 1 eye per subject was randomly included. The retinal nerve fiber layer (RNFL) was evaluated by means of OCT (Stratus OCT 3000). The sensitivity and specificity values of different diagnostic criteria (4 abnormal quadrants and 1–5 abnormal clock-hours) were calculated with different probability levels (p < 0.05 and p < 0.01). Results: The criterion with the best sensitivity-specificity balance was the presence of ≥2 hour positions with an RNFL thickness outside of the 95% confidence interval (CI; sensitivity = 77.2%, specificity = 91.9%). For the 99% CI, the best criterion was the presence of at least 1 abnormal hour position (sensitivity = 71.2%, specificity = 91%). Regarding retinal quadrants, the presence of at least 1 quadrant with RNFL thickness outside of the CI was the criterion that best discriminated the existence of glaucomatous damage. Conclusions: The definition of diagnostic criteria based on OCT structural parameters may improve its diagnostic ability. The highest diagnostic ability was provided by the presence of at least 2 hour positions or RNFL average thickness outside the 95% CI.