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Editors Selection IGR 11-2
Examination methods: Parapapillary autofluorescence
Comment by Brad Fortune on:
13826 Comparison of objective diagnostic tests in glaucoma: Heidelberg retinal tomography and multifocal visual evoked potentials, Balachandran C; Graham SL; Klistorner A et al., Journal of Glaucoma, 2006; 15: 110-116
A recent study by Balachandran et al. (416) compared the diagnostic performance of two 'objective' techniques for detection of
glaucoma. Their cross-sectional study consisted of 41 glaucoma patients recruited from a tertiary referral practice, and 25 age-matched healthy controls. The investigators used an AccuMap instrument to obtain multifocal visual evoked potentials (mfVEPs) and a Heidelberg Retina Tomograph (HRT II) to obtain topographic maps of the optic nerve head and peripapillary retinal surface. They used primarily the proprietary algorithms available within each instrument to determine a diagnosis for one eye of each subject in the study. The results were compared against a 'gold-standard' that was essentially the 'clinical' diagnosis. That is, glaucoma subjects were required to have both a repeatable scotoma on standard automated perimetry (SAP) and glaucomatous optic neuropathy (GON) to be included in the study, while controls were required to have both reliably normal SAP visual fields and a normal appearance of both optic discs.
After comparing sensitivity and specificity, and the area under the receiver operating characteristic (AUROC) curve for each parameter, the authors found that the mfVEP parameter known as the AccuMap Severity Index (ASI) had the highest diagnostic accuracy, followed by three structural diagnostic parameters from the HRT: the Moorfields Regression Analysis (MRA), the RB and the FSM discriminant functions. However, confidence intervals around each parameter's AUROC overlapped slightly, limiting capacity to infer that strong differences exist between parameters. Therefore the authors concluded that both objective tests "can detect glaucomatous damage." They stressed that "it remains important to look for both functional and structural changes in order to detect all glaucoma cases," because some cases were missed by one or the other technique.
Future studies are needed to further address the fundamental goal underscored by the title of this well-written paper. Although likely to be aided by a larger sample size, they might also need to overcome challenges such as differences between normative databases, limitations imposed by an imperfect gold-standard, and capture of information unaccounted by the current diagnostic algorithms.
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