Failure to achieve target IOP leads to more rapid visual field worsening

Treated patients who fail to achieve the target intraocular pressure (IOP) are at higher odds of experiencing more rapid visual field (VF) worsening, reports a study. Those with moderate glaucoma have the greatest VF worsening from such failure.

Longitudinal data were used in this retrospective analysis of 2,852 eyes of 1,688 patients with glaucoma-related diagnoses treated in a tertiary care practice. All included eyes had at least five reliable VF tests and five IOP measures on separate visits, along with at least one target IOP defined by a clinician on the first or second visit.

The slope of the mean deviation (MD) over time (decibels [dB]/year) was the primary dependent variable, while mean target difference (measured IOP ‒ target IOP) was the primary independent variable. Simple linear regression models and mixed-effects linear models were used to assess the association between MD slope and mean target difference for individual eyes.

In the mixed-effects models, the investigators included an interaction term to account for disease severity (mild/suspect, moderate, or advanced) and a spline term to account for the differing effects of achieving target IOP (target difference ≤0) and failing to achieve target IOP (target difference >0).

In a simple linear regression model, a 1-mm Hg increase in target difference showed a ‒0.018 dB/year (95 percent confidence interval [CI], ‒0.026 to ‒0.011; p<0.05) effect on MD slope across all eyes. The mixed-effects model demonstrated that a 1-mm Hg increase in target difference resulted in a ‒0.119 dB/year (95 percent CI, ‒0.168 to ‒0.70; p<0.05) worse MD slope across eyes with moderate disease that failed to achieve their target IOP.

“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-mm Hg increase in IOP had a −0.004 dB/year (95 percent CI, −0.011 to 0.003; p>0.05) effect on the MD slope,” the investigators said.