Outflow obstruction in pigmentary and primary open angle glaucoma

J. A. Alvarado and C. G. Murphy
Department of Ophthalmology, University of California School of Medicine, San Francisco 94143.

To localize the site of outflow obstruction in glaucoma, we evaluated the trabecular meshwork tissues by morphometric methods. Thirty-three specimens from 27 patients with primary open angle glaucoma (n = 13), pigmentary glaucoma (n = 4), and pigment dispersion syndrome (n = 2), and from nonglaucomatous normal subjects (n = 8) were compared. In these specimens, the extent of aqueous channels and the area occupied by these channels where they terminate in cul-de-sacs were measured. In 32 nonglaucomatous normal specimens (six of the eight mentioned plus an additional 26), we discovered that 94% of the surface area of the cul-de-sacs is lined by trabecular cells. These measurements were used to calculate the resistance to aqueous outflow offered by cul-de-sacs. Three new concepts are advanced in this report: (1) the cul-de-sacs provide a major portion of the normal outflow resistance, (2) the cul-de-sac area is markedly reduced in pigmentary glaucoma and primary open angle glaucoma, accounting for a major portion of the increase in resistance in these conditions, and (3) macrophages are the major cell type responsible for trabecular meshwork clearance of pigment and debris. A common pathophysiologic sequence of events is proposed for the development of glaucoma in pigmentary glaucoma and primary open angle glaucoma.

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