The Retinal Nerve Fiber Layer Analysis in Eyes with Small Optic Disc

PURPOSE: Eyes with small optic disc may be infirm to glaucomatous damage but suitable and objective methods for monitoring glaucomatous optic nerve damage in small optic disc are limited. The purpose of this study was to evaluate the usefulness of the retinal nerve fiber layer (RNFL) analysis using scanning laser polarimetry in patients with small optic disc. METHODS: 63 patients with small optic disc were recruited in this study. Eyes with average disc diameter 1.617 mm or less which was 33 percentile by topographic scanning system in our normal population study were enrolled. There were 26 patients with normal tension glaucoma and 37 patients with normal visual fields. Each patient underwent RNFL analysis using GDx VCC. Measurements of axial length, intraocular pressure, refractive error, disc diameter and cup/disc ratio were fulfilled. Findings were compared with independent t-test between 2 groups. GDx VCC parameters were analyzed with multiple logistic regression analysis. RESULTS: No differences in age, axial length, intraocular pressure, refractive error and disc diameter were apparent between the two groups. However, significant differences were detected in GDx VCC parameters including TSNIT average, Superior average, TSNIT standard deviation, NFI, Superior ratio, Inferior ratio, Sup/nasal, Maximum modualation, Superior maximum and Normalized superior area (p<0.001). The RNFL damage of superior area was prominent. CONCLUSIONS: In the patients with small optic disc, it is hard to detect the pathologic glaucomatous change by their disc morphologies. Therefore, RNFL analysis could be useful for a glaucoma screening of the patients with small optic disc.

Retinal Nerve Fiber Layer Thickness and Peripapillary Atrophy in Glaucoma with Small Discs

PURPOSE: To evaluate the usefulness of the retinal nerve fiber layer thickness and peripapillary atrophy in discrimination between normal and glaucoma patients with small optic discs which can be potentially misleading by cup-to-disc ratio. METHODS: Eyes with average disc diameter 1.617 mm or less which is 33 percentile by topographic scanning system (TopSST M, version 2.2, LDT, Inc., U.S.A) in our normal population study were enrolled. 82 eyes of 82normal subjects, 30 eyes of 30 patients with primary open-angle glaucoma (POAG), 16 eyes of 16 patientswith normal tension glaucoma (NTG) were studied. Program 30-2 of the Humphrey Field and scanning laser polarimetry (Nerve Fiber Analyzer II : NFAII, version 2.1., LDT, Inc., U.S.A.) were performed and color optic disc photographs had been taken. The differences in NFA parameters and peripapillary atrophy (zone alpha and zone beta) between normal subjects and glaucoma patients were examined. RESULTS: Considering all the NFA parameters, superonasal ratio of POAG and NTG group was significantly lower than normal group (p=0.002, p=0.043, respectively) and inferonasal ratio of POAG group was significantly lower than normal group (p=0.020). Zone beta atrophy was detected more frequently in POAG and NTG group than normal group (p=0.015, 0.007, respectively). No significant correlation was found between superonasal, inferonsal ratio and visual field indices and the presence of zone beta was not associated with progression of visual field. CONCLUSIONS: In small optic discs which had been presented diagnostic difficulties with optic disc status, retinal nerve fiber layer thickness (superonasal or inferonasal ratio) and/or peripapillary atrophy (zone beta) analysis can be helpful in identifying glaucoma.