Several investigators have described significant changes in visual function in ocular hypertensive and glaucoma-suspect eyes even though standard visual fields remain normal. Functional deficits in color vision, color visual fields, contrast sensitivity, flicker sensitivity, resolution, and motion detection have been documented. We review here the results from our laboratory and other laboratories on several of these tests. The relationship of these deficits to underlying physiology and a current theory that magnocellular fibers are damaged early in glaucoma are discussed. The evidence suggests that by the time glaucoma is diagnosed, based on characteristic changes in the optic disc, standard visual fields, and increased intraocular pressure, several visual functions are compromised. It is time to review the implications of these findings for diagnosis and management of glaucoma.