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The definition of glaucoma has changed over the decades from a simple ocular pressure disease to a systemic disorder of multivariate etiology. Glaucoma may be defined for the individual eye as a chronic ocular disease with various underlying pathophysiologic disorders. However, elevated intraocular pressure (IOP) is still the most important risk factor for an untreated glaucomatous eye to progress to a more severe stage of the disease. As the main risk factor within therapeutic reach, IOP and its appropriate measurement deserve our ongoing interest. Not only has our understanding of glaucoma changed but also our approach to the measurement of the IOP. In this article we focus our attention on the various developments in tonometry from the simple force-tonometers of the late 19th century to the high-technology pressure tonometers that were recently introduced for clinical use.

This set of Viewpoints articles examines the merits of beta-blockers versus other medications as the primary drug treatment for glaucoma. Ophthalmologists must balance issues such as efficacy, compliance, cost, and side effects when deciding on the appropriate medication to prescribe. Dr. Stamper stresses the advantages of tailoring the choice of medication to the needs of the individual patient. Drs. Wigginton and Higginbotham review the benefits of beta-blockers and present some of the disadvantages of the non-beta-blocker class of medications.

Chronic glaucoma has been thought to spare the central vision until quite late in the disease process. This assumption is based on the use of the relatively insensitive Snellen chart to measure central vision and the relatively sensitive kinetic and static perimetry to measure the peripheral vision. In recent years, new measures of visual function have been utilized to assess patients with glaucomatous damage. Sensitive methods of measuring central visual function such as color vision, contrast sensitivity (both spatial and temporal), and macular light sensitivity have demonstrated defects early in the glaucomatous process - sometimes even before perimetry is affected. Since these visual functions are largely mediated by macular fibers, central vision may be affected earlier and more frequently in glaucoma than previously believed. Studies of both the nerve fiber layer of the retina and of quantitative light sense perimetry suggest that glaucomatous damage may occur diffusely across the population of nerve fibers, focally in the arcuate portion of the nerve fiber layer, or in both places. Color vision, contrast sensitivity and macular light sense appear to correlate with the diffuse type of nerve fiber layer damage. The exact utility of the psychophysical tests that assess central visual function for the clinical management of glaucoma has not yet been demonstrated. More work is needed to determine which tests are most useful, what parameters are most efficient, and what the diagnostic and prognostic significance of abnormal values may be. However, the studies of color vision, contrast sensitivity and macular light sensitivity have led to a better understanding of how glaucoma affects visual function.