We analyzed 34 sets of optic disk photographs from 19 patients with glaucoma who had been followed up for ten years to evaluate changes in the position of the vasculature of the optic disks over time. Each photograph was analyzed by an image analyzer's edge-defining program for optic disk analysis and by three experienced clinicians. Image analysis of the blood vessels in 16 optic disks showed positional centrifugal shifts. The clinicians consistently noted changes in the appearance of seven optic disks. The difference between the results obtained using the image analyzer and those obtained by clinical observation was significant (P less than .05).