Ability of cirrus HD-OCT optic nerve head parameters to discriminate normal from glaucomatous eyes

Abstract

Purpose: To determine the ability of optic nerve head (ONH) parameters measured with spectral domain Cirrus HD-OCT (Carl Zeiss Meditec, Inc., Dublin, CA) to discriminate between normal and glaucomatous eyes and to compare them with the discriminating ability of peripapillary retinal nerve fiber layer (RNFL) thickness measurements performed with Cirrus HD-OCT.

Design: Evaluation of diagnostic test or technology.

Participants: Seventy-three subjects with glaucoma and 146 age-matched normal subjects.

Methods: Peripapillary ONH parameters and RNFL thickness were measured in 1 randomly selected eye of each participant within a 200 × 200 pixel A-scan acquired with Cirrus HD-OCT centered on the ONH.

Main outcome measures: Optic nerve head topographic parameters, peripapillary RNFL thickness, and area under receiver operating characteristic curves (AUCs).

Results: To distinguish normal from glaucomatous eyes, regardless of disease stage, the 6 best parameters (expressed as AUC) were vertical rim thickness (VRT, 0.963), rim area (0.962), RNFL thickness at clock-hour 7 (0.957), RNFL thickness of the inferior quadrant (0.953), vertical cup-to-disc ratio (VCDR, 0.951), and average RNFL thickness (0.950). The AUC for distinguishing between normal eyes and eyes with mild glaucoma was greatest for RNFL thickness of clock-hour 7 (0.918), VRT (0.914), rim area (0.912), RNFL thickness of inferior quadrant (0.895), average RNFL thickness (0.893), and VCDR (0.890). There were no statistically significant differences between AUCs for the best ONH parameters and RNFL thickness measurements (P > 0.05).

Conclusions: Cirrus HD-OCT ONH parameters are able to discriminate between normal eyes and eyes with glaucoma or even mild glaucoma. There is no difference in the ability of ONH parameters and RNFL thickness measurement, as measured with Cirrus OCT, to distinguish between normal and glaucomatous eyes.

Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Illustration of Cirrus HD-OCT Optic Nerve Head (ONH) Parameters (1A) and Determination of ONH Edge and Rim Width (1B, 1C and 1D). Figure 1A shows a sketch of an optic disc, as presented in the 2-dimensional en face view. The shaded region represents the neuro-retinal rim area (mm2), the patterned region is the area of the cup (mm2); the total area of the optic disc is the area of the rim plus the area of the cup (mm2). The cup-to-disc ratio (CDR) is given by the square-root of the ratio of the area of the cup to the area of the optic disc. The vertical cup-to-disc ratio (VCDR) is the ratio of the cup diameter to the disc diameter in the vertical meridian; VC/(VC+V1+V2). The horizontal cup-to-disc ratio (HCDR) is the ratio of the cup diameter to the disc diameter in the horizontal meridian; HC/(HC+H1+H2). Vertical rim thickness (VRT) is the disc diameter minus the cup diameter in the vertical meridian, or simply V1+V2, expressed in microns. Horizontal rim thickness is the disc diameter minus the cup diameter in the horizontal meridian; H1+H2 (microns). Cup volume (mm3) is a 3-dimensional measurement defined as the volume between a plane created by the cup outline at the vitreous interface and the posterior surface of the ONH. Figure 1B displays the disc perpendicular to viewing angle, where the optic disc and cup area are calculated in the plane of the ONH. The disc and rim areas are the same in Figures 1C and 1D. If the same disc is viewed from a different angle after entering the pupil from a different point, the displayed cup and disc are shortened as displayed in Figure 1C. However, the measurements are unaffected if they are calculated in the plane of the optic as in Figure 1B (Figure 1D).

Figure 2

Receiver Operator Characteristic Curves of the Best Parameters for Discriminating between Normal and Eyes with Moderate to Severe Glaucoma (2A) and of the Overall Best Six Parameters for Discriminating between Normal and Eyes with Mild Glaucoma (2B). VRT - Vertical Rim Thickness, Inf. - Inferior, VCDR - Vertical Cup-to-Disc Ratio, RNFL - Retinal Nerve Fiber Layer, Sup. - Superior, CDR - Cup-to-Disc Ratio, HCDR - Horizontal Cup-to-Disc Ratio.

Figure 3

Trend of the Ability of Vertical Rim Thickness (VRT), Rim Area, Average Retinal Nerve Fiber Layer (RNFL), and RNFL Thickness of the Inferior (Inf) Quadrant to Discriminate between Normal and Glaucomatous Eyes, Normal and Mild Glaucoma, and Between Moderate and Severe Glaucoma.