Discrimination between glaucomatous and nonglaucomatous eyes using quantitative imaging devices and subjective optic nerve head assessment

Abstract

Purpose: To compare the diagnostic ability of the confocal scanning laser ophthalmoscope (HRT-II; Heidelberg Engineering, Heidelberg, Germany), scanning laser polarimeter (GDx-VCC; Carl Zeiss Meditec, Inc., Dublin, CA), and optical coherence tomographer (StratusOCT, Carl Zeiss Meditec, Inc.) with subjective assessment of optic nerve head (ONH) stereophotographs in discriminating glaucomatous from nonglaucomatous eyes.

Methods: Data from 79 glaucomatous and 149 normal eyes of 228 subjects were included in the analysis. Three independent graders evaluated ONH stereophotographs. Receiver operating characteristic curves were constructed for each technique and sensitivity was estimated at 80% of specificity. Comparisons of areas under these curves (aROC) and agreement (kappa) were determined between stereophoto grading and best parameter from each technique.

Results: Stereophotograph grading had the largest aROC and sensitivity (0.903, 77.22%) in comparison with the best parameter from each technique: HRT-II global cup-to-disc area ratio (0.861, 75.95%); GDx-VCC Nerve Fiber Indicator (NFI; 0.836, 68.35%); and StratusOCT retinal nerve fiber layer (RNFL) thickness (0.844, 69.62%), ONH vertical integrated rim area (VIRA; 0.854, 73.42%), and macular thickness (0.815, 67.09%). The kappa between photograph grading and imaging parameters was 0.71 for StratusOCT-VIRA, 0.57 for HRT-II cup-to-disc area ratio, 0.51 for GDX-VCC NFI, 0.33 for StratusOCT RNFL, and 0.28 for StratusOCT macular thickness.

Conclusions: Similar diagnostic ability was found for all imaging techniques, but none demonstrated superiority to subjective assessment of the ONH. Agreement between disease classification with subjective assessment of ONH and imaging techniques was greater for techniques that evaluate ONH topography than with techniques that evaluate RNFL parameters. A combination of subjective ONH evaluation with RNFL parameters provides additive information, may have clinical impact, and deserves to be considered in the design of future studies comparing objective techniques with subjective evaluation by general eye care providers.

Figure 1

ROC curves were constructed for stereophotograph grading and for the best parameter from each imaging technique.

Figure 2

Venn diagrams showing the number of eyes classified as glaucomatous by stereophotograph grading and by the best parameter from each imaging technique. Imaging data were divided into (A) disc and (B) retinal nerve fiber layer (RNFL) parameters. n = 79 glaucomatous eyes, on the basis of standard perimetry alone. None of the techniques correctly identified all glaucomatous eyes. A combination of stereophotograph grading+GDx-VCC NFI+StratusOCT RNFL identified most glaucomatous eyes (70/79).