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David C. Musch, Leslie M. Niziol, Brenda W. Gillespie; A Critical Evaluation of Evidence for Visual Field Improvement in the CIGTS. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4479.
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To evaluate whether the occurrences of visual field (VF) improvement in CIGTS participants is real or due to random variation.
Humphrey 24-2 full threshold VF tests obtained in the CIGTS on 607 enrolled subjects with newly-diagnosed open-angle glaucoma were inspected for change over follow-up in mean deviation (MD). Clinically substantial change (loss or improvement) was defined as any change from baseline of 3 or more decibels in MD. Baseline factors that have been reported to be predictive of long-term VF loss in the CIGTS (Musch DC et al., Ophthalmology 2009; 116:200-7) were inspected to determine the extent and direction of their association with VF improvement in exploratory repeated measures logistic regression models. SAS 9.2 Proc Genmod software was used for regression analyses.
The percentage of CIGTS participants who showed substantial VF improvement over time was similar to that showing VF loss through five years after initial treatment, after which VF loss became more frequent. For example, at 1, 3, and 5 years after initiation of treatment, substantial VF loss/improvement was observed in 6.6%/7.5%, 10.9%/12.7%, and 14.5%/13.9%, respectively. At seven years, occurrences of substantial VF loss (19.6%) were more frequent than VF improvement (13.5%). Significantly predictive factors for VF improvement from regression models included female sex [odds ratio (OR)=1.73, 95% confidence interval (CI) = 1.17, 2.56], visit one year prior to cataract extraction (OR=0.11, 95% CI=0.02, 0.62), and an interaction between treatment and baseline MD in which those with VF improvement were more likely to be treated initially with surgery and, within treatment groups, more likely among those with more VF loss at baseline (a more negative MD). Several measures of IOP control during treatment were also predictive of VF improvement, including a lower mean IOP, lower minimum IOP, and a number of measures relating to maintenance of lower IOP throughout follow-up (e.g., proportion IOP<16 mmHg: OR=2.18, 95% CI = 1.21, 3.93).
In the CIGTS, comparable percentages of participants demonstrated either substantial VF loss or improvement through five years after treatment initiation, after which the percentage that showed VF loss became more frequent. Predictive factors for VF improvement include some that are consonant with the postulate that VF improvement is real, such as measures of better IOP control over time.
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