Optic disc rim area to retinal nerve fiber layer thickness correlation: comparison of diabetic and normal tension glaucoma eyes.

PURPOSE: To compare the correlation between optic disc rim area and retinal nerve fiber layer thickness (rim-RNFL correlation) in diabetic eyes with non-progressive RNFL defects and normal tension glaucoma (NTG) eyes.
METHODS: Seventy-three eyes of 73 patients with preperimetric or early NTG and 25 eyes of 25 type II diabetes patients with a non-progressive RNFL defect for ≥5 years were enrolled in this retrospective cohort study. Rim areas and RNFL thicknesses were measured by Heidelberg retina tomography (HRT II) and by optical coherence tomography (Cirrus OCT), in global and 12 clock-hour parameters. Diabetic eyes were evaluated whether they were above the 95 % prediction interval (PI) for the rim-RNFL correlation of NTG.
RESULTS: A significant linear rim-RNFL correlation was observed in NTG eyes globally and at all clock-hours, except in the 4 and 9 o'clock areas, (0.08 < r (2) < 0.56, P < 0.05). Eighty-four percent of the diabetic eyes were above the 95 % PI of the rim-RNFL correlation of NTG in ≥2 clock-hours, as compared with 36 % of the eyes in the global parameter.
CONCLUSIONS: The eyes of diabetic patients with non-progressive RNFL were well-differentiated from NTG eyes by the rim-RNFL correlation.