Purpose: To compare patients becoming legally blind from glaucoma with those who did not go blind.
Design: Retrospective, cohort, and case-control study.
Methods: A retrospective community-based longitudinal study of residents of Olmsted County, Minnesota, who were newly diagnosed with open-angle glaucoma between 1965 and 1980 and followed through 1998. A case-control study was performed comparing patients progressing to legal blindness from glaucoma with aged-matched and visual field-matched patients not progressing to blindness.
Results: Fifty-six of 290 patients progressed to legal blindness in at least one eye over the 34-year period of the study. Most who progressed to blindness had moderate to advanced visual field loss at the time of diagnosis of glaucoma. Those becoming legally blind had mean intraocular pressures (IOP) on therapy lower than or similar to patients who did not go blind, although the variability of IOP was higher in the blind group. Different susceptibilities to IOP were apparent, as some eyes with initially normal disks and visual fields became blind at an IOP of 20 mm, while others did not worsen. Changes in medical therapy after progression of visual field damage were less effective in lowering IOP in the group becoming blind than in the nonblind group.
Conclusions: Patients at greatest risk of blindness had visual field loss at the time of diagnosis of glaucoma. Different susceptibilities to IOP were apparent, with some patients becoming blind at pressures that others tolerated without significant progression. This suggests that continued monitoring of visual fields and reassessment of target IOP levels when field damage occurs are fundamental in the management of glaucoma.