Purpose: To evaluate optical coherence tomography (OCT) parameters in patients with concomitant type-2 diabetes mellitus (DM) and primary open angle glaucoma (POAG) compared with patients with either of these diseases.
Methods: Sixty eyes (52 patients) were divided into three groups. The first group included nonglaucomatous diabetic patients, the second included patients with POAG without DM, and the third included patients with both POAG and DM. Spectral domain OCT evaluation of the retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and optic disc parameters was performed. Visual field (VF) was measured for structural and functional correlation.
Results: Significant differences were found in average RNFL, inferior RNFL, average GCC, inferior GCC, rim area, focal loss volume (FLV%), and global loss volume (GLV%) (P = 0.014, 0.001, 0.027, 0.006, 0.009, 0.043, and 0.001, respectively). The concomitant presence of DM and glaucoma was a risk factor for decreased average RNFL, inferior RNFL, rim area, and inferior GCC, and for increased GLV% (P = 0.034, 0.002, 0.014, 0.015, and 0.003, respectively). The inferior RNFL thickness had the largest significant area under the curve (P = 0.726; 90% sensitivity) at a specificity greater than 80% with a cutoff value of 105.38 μm (P = 0.005) compared with average RNFL, inferior GCC, rim area, and GLV% (P = 0.073, 0.25, 0.23, and 0.1, respectively). VF demonstrated the predominance of nasal scotomata in the diabetic group and arcuate scotoma in the glaucoma group (P < 0.001 and 0.03, respectively).
Conclusions: OCT could be a valuable tool for the detection and follow-up of POAG in diabetic patients. The inferior RNFL thickness could be a sensitive and a specific predictor for glaucoma diagnosis and progression in diabetic patients without retinopathy.
Keywords: Diabetes mellitus; Ganglion cell complex; Primary open angle glaucoma; Retinal nerve fiber layer; Spectral domain optical coherence tomography.