Densitometric Profiles of Optic Disc Hemorrhages in the Ocular Hypertension Treatment Study

PURPOSE: The origin of blood in glaucoma-related disc hemorrhages (DH) remains unknown. A prior clinic-based study of primary open-angle glaucoma (POAG)-related DH showed that they had grayscale pixel intensities more similar to blood from retinal macroaneurysms and adjacent retinal arterioles than to blood from retinal vein occlusions or adjacent retinal venules, suggesting an arterial source. Here we assessed the densitometric profile of DH from fundus photographs in the Ocular Hypertension Treatment Study (OHTS). DESIGN: Retrospective cross-sectional study of prospectively collected images. METHODS: Stereo disc photographs of 161 DH events from 83 OHTS participants (mean age (standard deviation (SD)): 65.6 (9.2) years; 46.6% female; 13.0% black race) were imported into ImageJ to measure densitometry differences (adjacent arterioles minus DH (ΔA) or venules minus DH (ΔV)). Their size as percentage of disc area, ratio of length to midpoint width, and location relative to the disc margin were also analyzed. We performed t-tests to compare ΔA and ΔV, analysis of variance to compare ΔA and ΔV across DH recurrent events, and multivariable linear regression to identify determinants of ΔA and ΔV. RESULTS: Mean (SD) ΔA and ΔV were −2.2 (8.7) and −11.4 (9.7) pixel intensity units, respectively (P