Does the visual field improve after initiation of intraocular pressure lowering in the United Kingdom Glaucoma Treatment Study?

Abstract

PurposeEvidence to support the hypothesis that visual field (VF) status can improve after initiation of intraocular pressure (IOP) reducing treatment is controversial. We take advantage of participant eligibility data from the United Kingdom Glaucoma Treatment Study (UKGTS) to test this hypothesis in newly diagnosed glaucomatous patients randomised to IOP lowering therapy or placebo. DesignMulticentre, randomised, triple-masked, placebo-controlled trial. ParticipantsNewly diagnosed open-angle glaucoma patients in the UKGTS with eligibility and baseline data (n = 202 and n = 205 participants from the treatment and placebo groups, respectively). MethodsUKGTS eligibility data, including two reliable VFs (Humphrey 24-2 SITA Standard) and IOP measurements were compared to UKGTS trial baseline data acquired after allocation to treatment (topical prostaglandin analog) or placebo eye drops. Mean change in VF mean deviation (MD) and proportion of eyes that improved MD by more than different thresholds were compared across this interval in the treatment and placebo groups. Secondary analyses included stratifying the groups by level of IOP, level of VF loss and age along with pointwise analyses including change in subsets of VF locations. Main outcome measureMean change in VF MD. ResultsMean (standard deviation [SD]) time between eligibility/baseline visits and reduction in IOP was 12 (3) weeks and 4.8 (4.2) and 1.0 (3.6) mmHg for the treated and placebo eyes, respectively. Mean (SD) change in MD was almost the same for the treated (-0.03 (1.45) dB) and placebo groups (+0.08 (1.72) dB) (P=0.47). Proportion of participants with an MD improvement of 1 dB or more were similar for both groups (P=0.25). No association was found between MD improvement and magnitude of IOP lowering. Stratifying data by IOP, level of VF loss and age did not reveal any differences between the treated and placebo groups and neither did any of the pointwise VF analyses. ConclusionInitial short-term VF changes in the treatment and placebo arms of UKGTS were the same. In these newly diagnosed patients (non-advanced glaucoma) we found no evidence to support the hypothesis that VF status improves after initial lowering of IOP by medical therapy.