The Effect of Achieving Target Intraocular Pressure on Visual Field Worsening

Abstract

To estimate the effect of achieving target intraocular pressure (IOP) values on visual field (VF) worsening in a treated clinical population. Retrospective analysis of longitudinal data. A total of 2852 eyes of 1688 patients with glaucoma-related diagnoses treated in a tertiary care practice. All included eyes had at least 5 reliable VF tests and 5 IOP measures on separate visits along with at least 1 target IOP defined by a clinician on the first or second visit. The primary dependent variable was the slope of the mean deviation (MD) over time (decibels [dB]/year). The primary independent variable was mean target difference (measured IOP - target IOP). We created simple linear regression models and mixed-effects linear models to study the relationship between MD slope and mean target difference for individual eyes. In the mixed-effects models, we included an interaction term to account for disease severity (mild/suspect, moderate, or advanced) and a spline term to account for thediffering effects of achieving target IOP (target difference ≤0) and failing to achieve target IOP (target difference >0). Rate of change in MD slope (changes in dB/year) per 1 mmHg change in target difference at different stages of glaucoma severity. Across all eyes, a simple linear regression model demonstrated that a 1 mmHg increase in target difference had a-0.018 dB/year (confidence interval [CI],-0.026 to-0.011; P < 0.05) effect on MD slope. The mixed-effects model shows that eyes with moderate disease that fail to achieve their target IOP experience the largest effects, with a 1 mmHg increase in target difference resulting in a -0.119 dB/year (CI,-0.168 to-0.070; P< 0.05) worse MD slope. The effects of missing target IOP on VF worsening were more pronounced than the effect of absolute level of IOP on VF worsening, where a 1 mmHg increase in IOP had a-0.004 dB/year (CI,-0.011 to 0.003; P > 0.05) effect on the MD slope. In treated patients, failing to achieve target IOP was associated with more rapid VF worsening. Eyes with moderate glaucoma experienced the greatest VF worsening from failing to achieve target IOP.