This application describes a competitive renewal for an additional five years of funding for an ancillary study to the Ocular Hypertension Treatment Study (OHTS), a multicenter clinical trial sponsored by the National Eye Institute, to determine the effectiveness of confocal scanning laser ophthalmoscopy to objectively evaluate the optic disc in ocular hypertensive patients. The OHTS is currently funded through 2002. Specific Aims: 1. To evaluate the use of confocal scanning laser imaging techniques to detect glaucomatous optic nerve damage and change in ocular hypertensive patients. 2. To investigate the quantitative temporal relationship between optic nerve topography and measurable visual field loss. 3. To evaluate the effect of treatment on optic nerve topography. 4. To compare topographic optic disc parameters in African-American and White ocular hypertensive patients. Methods: Seven of the 21 OHTS study centers will participate in this ancillary study; 450 ocular hypertensive patients have consented to participate in the study. At least 389 (86 percent) are still active in the study; 137 (30 percent) have over 3 years of follow-up. Confocal laser scanning ophthalmoscopy is being used to measure optic disc and peripapillary topography at the randomization visit, and annually thereafter for the duration of the study. The Confocal Scanning Laser Ophthalmoscopy Reading Center at University of California, San Diego is responsible for processing and analyzing the images. The CSLO Reading Center provides the OHTS Data Coordinating Center with topographic optic disc data monthly. To ensure that this ancillary study will not jeopardize recruitment, retention, implementation of the primary trial or assessment of the primary findings, the reading center is masked to identity and treatment status of all patients. These data will be evaluated quantitatively for evidence of glaucomatous damage and change, and compared with other structural and functional measures of glaucomatous optic neuropathy obtained in the OHTS. This study will evaluate whether these advances in fundus imaging technology can improve the precision with which we can detect and monitor glaucomatous optic neuropathy.