Discrimination between Glaucomatous and Nonglaucomatous Eyes Using Quantitative Imaging Devices and Subjective Optic Nerve Head Assessment

In an effort to detect and document changes indicative of glaucoma at earlier stages, a variety of techniques have evolved to provide quantitative estimates of optic nerve head (ONH) topography, retinal nerve fiber layer (RNFL) thickness, and macular thickness. Several studies have demonstrated that in prior versions each of some of these techniques discriminate between glaucomatous and normal populations with a high degree of sensitivity and specificity.1–5 However, few studies have compared the diagnostic performance of these instruments in the same study population and in comparison to subjective assessment of the ONH.1,3 These prior studies used older versions of the instruments and demonstrated that objective optic nerve imaging modalities were equivalent to subjective assessment performed by masked expert stereophotograph graders. Since the earlier studies, significant modifications have occurred with each of these quantitative imaging techniques that have improved their ability to detect glaucomatous damage. With scanning laser polarimetry (GDx-VCC; Carl Zeiss Meditec, Inc., Dublin, CA), a conversion to variable corneal compensation that provides individualized adjustment of anterior segment birefringence has improved the sensitivity and specificity of this technique.6,7 The current generation of optical coherence tomography (StratusOCT; Carl Zeiss Meditec, Inc.) has increased scan rate and scan resolution and can also be used to obtain macular and ONH measurements.8 The most recent version of the confocal scanning laser ophthalmoscope (HRT II; Heidelberg Engineering, Heidelberg, Germany) has been modified significantly with automation of the examination procedure focused on optic disc topography, which has improved the reproducibility and efficacy of this instrument in the detection of glaucoma.2,4,9,10 A recent study by Medeiros et al.11 using the current version of these instruments has demonstrated that each performs with similar efficacy in the diagnosis of glaucoma. However, there was no comparison between these new versions of objective imaging methods with subjective ONH evaluation or objective evaluation of the optic nerve head with ONH analysis and macular thickness from StratusOCT. The purpose of this study was to compare the diagnostic ability of the confocal scanning laser ophthalmoscopy with the HRT II, scanning laser polarimetry with the GDX-VCC, and retinal nerve fiber layer thickness, ONH analysis and macular thickness measurements with the StratusOCT with subjective masked expert assessment of stereophotographs in the same study population.