To compare retinal nerve fiber layer (RNFL) thicknesses with two types of OCT in patients with normal tension glaucoma (NTG) and early NTG.

We evaluated the RNFL thicknesses of 101 eyes in 101 patients using Fourier domain OCT and time domain OCT. We compared the measured RNFL thicknesses according to the subject groups and the type of OCT. We calculated the area under the receiver operating characteristic curve (AUROC) to determine the best parameters with which to make a diagnosis of NTG or early NTG.

The RNFL thicknesses measured by 3D OCT were greater than that measured by Stratus OCT for all of the groups. The RNFL thickness in each group was statistically significantly different in the superior quadrant, the inferior quadrant, and the 1 and 2 o'clock positions when using 3D OCT. It was statistically significantly different in the superior, temporal, and inferior quadrant, as well as the 1, 7, 8, 9, 10 and 11 o'clock positions when using Stratus OCT. The largest AUROC was found for the inferior quadrant thickness (0.773) using Stratus OCT and the 1 o'clock thickness (0.712) using 3D OCT when comparing normal patients and those with suspected NTG. The largest AUROC was found for the inferior quadrant thickness (0.888) using Stratus OCT and the superior quadrant thickness (0.802) using 3D OCT when comparing normal patients and those with early NTG. The AUROC was greater in the temporal and inferior quadrants and in the 6, 7, 8, 9 and 10 o'clock thicknesses using Stratus OCT compared to the 3D OCT in differentiating patients with suspected NTG from normal patients. The AUROC found using 3D OCT compared to the Stratus OCT was greater only in the 1 o'clock thickness ( p <0.05). The AUROC differentiating patients with early NTG from normal patients was greater in the temporal, inferior, nasal quadrant, and in the 5, 6, 7, 8, 9, 10 and 11 o'clock positions using the Stratus OCT compared to the 3D OCT ( p <0.05).

The RNFL thicknesses measured using 3D OCT were generally greater than those measured using Stratus OCT. The largest AUROCs for differentiating patients with suspected NTG and early NTG from normal patients were in the 1 o'clock position and the superior quadrant RNFL thickness using 3D OCT and the inferior quadrant RNFL thickness using Stratus OCT. The AUROCs using the 3D OCT parameters were less than those from the Stratus OCT when comparing normal patients and those with suspected or early NTG.