The use of ocular coherence tomography in evaluating optic nerve health in eyes with large disc size

Abstract

Large discs are often associated with large cups; in order to exclude glaucomatous cupping a good objective tool is needed. The purpose of this study is to evaluate ocular coherence tomography (OCT) optic nerve head (ONH) parameters as indicators of ocular health in subjects with large discs. Eighty-one eyes of 53 healthy patients were evaluated; 46 eyes had large discs (disc area ≥2.6 mm2) and 35 eyes had regular size discs (disc area <2.6 mm2). All subjects underwent OCT. All ONH parameters were documented, including vertical integrated rim area (VIRA), horizontal integrated rim width (HIRW), rim area, cup area, cup-to-disc (CD) area ratio, horizontal cup to disc ratio (HCDR), vertical cup to disc ratio (VCDR), cup area topography, and cup volume. In addition, OCT retinal nerve fiber layer (RNFL) global mean thickness and four quadrants mean thicknesses were analyzed. All cup parameters were significantly higher in the large disc group compared to the normal disc group. The parameters estimating the rim varied between the groups: in the large disc group VIRA was significantly lower while HIRW was significantly higher, compared to the control group. Rim area was the only parameter with similar values in both groups (1.52±0.24 mm2 and 1.6±0.3 mm2 in the large and regular disc groups, respectively). Correlation analysis revealed significant positive association between disc area and cup parameters in the large disc group. In contrast, in the regular disc group, disc area was positively associated with rim parameters. Rim area might serve as an indicator for ocular health in large discs with large cups.