Visual field improvement in the collaborative initial glaucoma treatment study.

Purpose: To evaluate critically visual field (VF) improvement in participants in the Collaborative Initial Glaucoma Treatment Study (CIGTS).

Design: Prospective, comparative case series from a randomized clinical trial comparing trabeculectomy and topical medications in treating open-angle glaucoma (OAG).

Methods: A total of 607 subjects with newly diagnosed OAG were identified for study. Baseline and follow-up VF tests were obtained and mean deviation (MD) change from baseline over follow-up was analyzed. Clinically substantial change (loss or improvement) was defined as change from baseline of ≥ 3 decibels in MD. Baseline factors were inspected to determine their association with VF improvement in repeated measures regression models.

Results: The percentage of participants showing substantial VF improvement over time was similar to that showing VF loss through 5 years after initial treatment, after which VF loss became more frequent. Measures of better intraocular pressure (IOP) control during treatment were significantly predictive of VF improvement, including a lower mean IOP, a lower minimum IOP, and lower sustained levels of IOP over follow-up. Other predictive factors included female sex (odds ratio [OR] = 1.73), visits 1 year prior to cataract extraction (OR = 0.11), and an interaction between treatment and baseline MD wherein surgically treated subjects with worse baseline VF loss were more likely to show VF improvement.

Conclusions: In the CIGTS, substantial VF loss and improvement were comparable through 5 years of follow-up, after which VF loss became more frequent. Predictive factors for VF improvement included several indicators of better IOP control, which supports the postulate that VF improvement was real.