Evaluation of scanning resolution on retinal nerve fiber layer measurement using optical coherence tomography in normal and glaucomatous eyes

Purposes: To evaluate the effect of varying the scanning resolution of optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) measurement on diagnostic sensitivity and functional correlation in glaucoma. Patients and Methods: 314 eyes from 182 subjects including 107 normal eyes, 83 glaucoma suspect eyes, and 124 glaucoma eyes were included in this cross-sectional study. Standard automated perimetry and OCT measurement of RNFL thickness were performed. Each individual underwent two scanning protocols: (1) fast RNFL thickness (3.4) scan (with resolution of 256 scan points) and (2) RNFL thickness (3.4) scan (with resolution of 512 scan points). RNFL thickness was compared among the groups. Diagnostic sensitivity was evaluated with Receiver Operating Characteristic (ROC) Curve. Relationship between RNFL thickness and visual field mean deviation was examined using linear regression analysis. Results: Measured RNFL thickness using fast RNFL thickness (3.4) scan was significantly higher compared with RNFL thickness (3.4) scan in average, superior, nasal and inferior RNFL in all diagnostic groups. Comparing normal and glaucoma groups, RNFL thickness (3.4) scan produced the largest area under the ROC curve (0.912) based on average RNFL thickness. A stronger, correlation between average RNFL and visual field mean deviation was found in RNFL thickness (3.4) scan (R = 0.75, R-2 = 0.56). Conclusions: Higher resolution RNFL scan provides better diagnostic sensitivity in glaucoma detection and a stronger correlation with visual function.