Purpose: To determine the effect of intraocular pressure (IOP) lowering on the optic disc in patients of the Collaborative Initial Glaucoma Treatment Study (CIGTS) after 5 years. Design: Randomized clinical trial. Methods: The baseline and 5-year stereoscopic optic disc photographs of 348 eyes (patients) randomized to medical or surgical treatment of open-angle glaucoma (OAG) were assessed by 2 independent readers for change in a masked side-by-side comparison, and confirmed by an independent committee. Results: Three hundred and three (87.1%) eyes showed no change, 22 (6.3%) showed enlargement of the cup along any meridian (progression), and 23 (6.6%) showed a reduction in the cup along any meridian (reversal of cupping). Incidence of optic disc progression was higher (P = .007) in the medicine group, 18/185 (10%) than in the surgical group 4/163 (3%); and the incidence of reversal of cupping was higher (P < .001) in the surgical group, 21/163 (13%), than the medicine group, 2/185 (1%), (P < .001). Visual field (VF) worsening (mean deviation) was significantly associated with progression of optic disc cupping (P < .001). Reversal of cupping was also associated with lower postoperative IOP (P < .001). Reversal of cupping was not associated with improvement of either visual acuity or central VFs. Conclusions: Surgery prevents or delays glaucomatous progression as measured by optic disc criteria in patients with early OAG. Reversal of cupping occurs more frequently in the surgical group than in the medical treatment group. Reversal is associated with lower IOP, but is not associated with improved visual function.
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