Early diagnosis in glaucoma

This chapter reviews the evidence for the clinical application of vision function tests and imaging devices to identify early glaucoma, and sets out a scheme for the appropriate use and interpretation of test results in screening/case-finding and clinic settings. In early glaucoma, signs may be equivocal and the diagnosis is often uncertain. Either structural damage or vision function loss may be the first sign of glaucoma; neither one is consistently apparent before the other. Quantitative tests of visual function and measurements of optic-nerve head and retinal nerve fiber layer anatomy are useful to either raise or lower the probability that glaucoma is present. The posttest probability for glaucoma may be calculated from the pretest probability and the likelihood ratio of the diagnostic criterion, and the output of several diagnostic devices may be combined to achieve a final probability. However, clinicians need to understand how these diagnostic devices make their measurements, so that the validity of each test result can be adequately assessed. Only then should the result be used, together with the patient history and clinical examination, to derive a diagnosis.