Challenges in glaucoma diagnosis in small optic discs: An OCT-based analysis

This study aimed to assess how optic disc (OD) size influences structural and functional tests in patients with glaucoma with small and normal-sized discs and to compare the sensitivities of these tests. The study comprised 182 eyes, including 109 eyes of 73 patients diagnosed with glaucoma and 73 eyes of 41 healthy subjects. Eyes were classified according to OD size as either small (<1.6 mm2) or normal (1.6-2.1 mm2). Optic nerve head parameters, peripapillary retinal nerve fiber layer (RNFL) thickness, and macular ganglion cell analysis were assessed using Cirrus 4000 spectral-domain optical coherence tomography. The sensitivities of RNFL, macular ganglion cell-inner plexiform layer (GCIPL), and visual field parameters were evaluated using logistic receiver operating characteristic regression analysis. The mean ages of the patients and controls were 65.48 ± 7.94 years and 65.22 ± 6.55 years, respectively (P = .859). The mean disc diameter was 1.48 ± 0.11 mm in the small-disc group and 1.86 ± 0.16 mm in the normal-disc group. The mean deviation values were -5.52 ± 4.81 and -4.54 ± 3.73 in the small- and normal-disc groups, respectively (P = .268). Among patients with glaucoma and small ODs, GCIPL parameters (mean, minimum, superior, and inferior hemifield values) demonstrated greater sensitivity than RNFL parameters. In contrast, RNFL parameters (average, superior, inferior, and corresponding hemifield values) showed greater sensitivity than GCIPL parameters in patients with normal-sized ODs. Macular structural parameters demonstrated higher sensitivity for glaucoma diagnosis in patients with small ODs. However, a comprehensive assessment integrating both macular and peripapillary structural parameters may improve diagnostic accuracy by providing complementary information in these patients.