The Optimal Diameter for Circumpapillary Retinal Nerve Fiber Layer Thickness Measurement by SD-OCT in Glaucoma.

Purpose: To evaluate the diagnostic power for glaucoma detection using circumpapillary retinal nerve fiber layer (cRNFL) thickness in 3 diameter sizes from the center of the optic nerve head (ONH) by spectral domain optical coherence tomography.

Patients And Methods: In this cross-sectional study, case-control, 437 eyes diagnosed with glaucoma and 183 eyes of healthy controls underwent spectral domain optical coherence tomography of the ONH, visual field testing, and a clinical examination. cRNFL was measured by circular scans in 3.5 (C1), 4.1 (C2), and 4.7 mm (C3) distance from the center of the ONH. Receiver-operator characteristic analysis was used to assess diagnostic power to detect glaucoma; furthermore, patient-specific maximum localized damage was analyzed.

Results: In C1, mean global cRNFL was 70.03±18.2 μm in glaucomatous eyes and 93.46±9.9 μm in controls. Respectively, cRNFL in C2 was 61.39±14.9 and 80.43±8.4 μm as well as 55.25±12.8 and 70.70±6.7 μm in C3. Using receiver-operator characteristic analysis, the area under the curve (AUC) for cRNFL was 0.855 in C1, 0.850 in C2, and 0.843 in C3. Mean AUCs in ONH sectors ranged from 0.699 to 0.846 and did not exceed AUC of the best scoring global parameter.

Conclusions: Comparing 3.5, 4.1, and 4.7 mm diameters for cRNFL measurement, the inner circle at 3.5 mm distance showed the highest AUC to differentiate glaucoma from healthy controls. However, levels of diagnostic power from wider circular scans were not significantly different and were comparable. Moreover, sectorial cRNFL measurements were nonsuperior. The use of the ONH sector with the highest localized damage seems not to increase diagnostic power.