Externalization of Schlemm's canal (sinusotomy) in glaucoma.

IT is evident that ocular hypertension in glaucoma is usually due to an increased resistance to the outflow of the intra-ocular fluid. In about two-thirds of all patients there is no visible obstacle to the outflow in the anterior chamber angle (so-called wide-angle glaucoma); these pathological changes in the intramural pathways, starting from the trabecular mesh- work, are usually held responsible for the circulatory disturbance. Some authors consider the trabecular zone as the site actually affected (Teng, Katzin, and Chi, 1957; Speakman, 1961). Grant (1958) pointed out that this area-accounted for about 75 per cent. of the normal resistance to outflow, but this is not necessarily the site of the pathological process. There are sound arguments in favour of the theory that the outflow is affected in the region of the intrascleral collectors between Schlemm's canal and the anterior ciliary veins (Duke-Elder, 1955; Dvorak-Theobald and Kirk, 1956).