How should diagnostic tests be evaluated in glaucoma?

Clinicians are faced each day with the challenge of deciding appropriate management for patients suspected of having glaucoma. This decision is, at least in part, based on the results of diagnostic tests. The continuing proliferation of medical technology and introduction of new diagnostic tests renders the clinician’s ability to critically evaluate these tests more important than ever. In the study by Reus and colleagues,1 published in this edition of the Journal, they evaluated the diagnostic accuracy of two imaging technologies – GDx VCC and HRT I – and compared that with subjective assessment of stereoscopic photographs of the optic nerve head. These three methods were evaluated in their ability to discriminate subjects who had glaucomatous visual field loss and corresponding optic nerve head changes from healthy individuals with normal visual fields and normal optic nerves. Their comparison provides further insight into the ability of these technologies to detect known glaucomatous damage and provides an important comparison with subjective methods that have long been in use such as stereophotograph evaluation.

Most diagnostic studies in glaucoma have employed a case-control design similar to the one used in the work by Reus et al,1 including glaucoma patients (cases), defined based on the presence of repeatable characteristic glaucomatous visual field defects; and normal subjects (controls), generally required to have normal visual fields, normal intraocular pressures and healthy appearance of the optic nerve. These studies are clearly important to provide an initial exploratory …