Newer visual function tests in the evaluation of glaucoma

Conventional visual field testing, with a uniform white-on-white stimulus, is used routinely to diagnose and follow patients with chronic open-angle glaucoma. Many investigators, however, believe that conventional perimetry may not detect the earliest visual dysfunction in patients with chronic open-angle glaucoma. Consequently, much research has been performed over the past decade to develop a visual function test which might diagnose chronic open-angle glaucoma earlier than conventional perimetry. This review discusses the mechanisms, clinical studies and the current usefulness of the most common new visual function techniques. These tests attempt to detect early glaucomatous visual loss, generally by placing the visual system under stress and by minimizing the influence of extensive functional redundancy in the retinal ganglion cell network due to widely overlapping receptive fields. Success of new visual function tests depends on the specificity and the sensitivity of the instrument, excellent patient acceptance, short test duration, standardization of techniques, and limited expense. In addition to searching for newer visual function tests to evaluate glaucoma, we should continue efforts to improve the diagnostic capability and shorten the test duration of conventional perimetry.