Increased vascular permeability in disc swelling produced by ocular hypotony.

Chronic hypotony and swelling of the optic disc was produced in monkey eyes by ciliary body freezing. Associated changes in vascular permeability were detected with horseradish peroxidase (HRP) used as a marker of vascular integrity. Extravascular infiltration of HRP was seen in eyes with disc swelling in the lamina retinalis, lamina choroidalis, lamina scleralis and retrolaminar myelinated portion of the nerve head. In the anterior lamina retinalis, HRP was found in perivascular connective tissue and in interaxonal spaces around some vessels. Our findings suggest that the major source of extravascular HRP in the optic nerve head in disc swelling is leakage from the choriocapillaris through the perineural connective tissues, although focal leakage from vessels in the anterior portions of the swollen disc probably also occurs.