Achieving clinician-defined target IOP affects change in visual field
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Patients with glaucoma who did not achieve clinician-defined target IOP had more rapid visual field worsening, according to data published in Ophthalmology.
While other studies have explored the effects of achieving prespecified target IOP, few have studied the clinician-set target.
“The tertiary objective of this study is to understand whether target difference is more strongly associated with VF worsening than the absolute level of IOP,” Gabriel A. Villasana, of the Malone Center for Engineering in Healthcare at Johns Hopkins University, and colleagues wrote. “We hypothesize that target difference will have a stronger influence on VF worsening than absolute IOP levels and that the stage of glaucoma and absolute level of target difference will modify the effect of target difference on VF worsening.”
In a retrospective analysis of longitudinal data, the researchers assessed 2,852 eyes of 1,688 participants who were evaluated at Wilmer Eye Institute between 2013 and 2020. All participants had a glaucoma-related diagnosis, and all eyes had at least five visual field (VF) tests and five IOP measurements from separate visits, in addition to one target IOP defined by a clinician at the first or second visit.
Using simple linear regression models and mixed effects linear models, the researchers observed the relationship between mean deviation (MD) slope and mean target difference for individual eyes.
The primary outcome of the study was rate of change in MD slope per 1 mm Hg change in target difference at different stages of glaucoma severity, according to the study.
A 1 mm Hg increase in target difference had a –0.018 dB per year effect (P < .05) on MD slope in all eyes. Data from the mixed effects model revealed that eyes with moderate disease that did not achieve target IOP had the largest effect, with a 1 mm Hg increase in target difference resulting in a 0.119 dB per year worse MD slope (P < .05). Meanwhile, the effect of absolute level of IOP on VF worsening was less pronounced, with a 1 mm Hg increase in IOP having a –0.004 dB per year effect on the MD slope.
“On the whole, we demonstrated that failing to achieve clinician-defined target IOP was associated with VF worsening, more so than absolute levels of IOP,” Villasana and colleagues wrote. “Furthermore, there was a difference in effect across disease stages, with moderate eyes experiencing stronger effects on VF worsening when failing to achieve clinician-defined target IOP.”
Perspective
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In addition to being an important risk factor for glaucoma, IOP) is also the only modifiable risk factor, and lowering IOP is the only proven treatment for this sight-threatening disease. Although it sounds straightforward, setting a treatment goal is not an exact science, and some elect not to set target IOPs for their patients.
To evaluate the potential benefit of setting target IOPs, Villasana and colleagues performed a retrospective analysis of longitudinal data and determined that failing to achieve target IOP was associated with more rapid VF worsening. Additionally, eyes with moderate glaucoma experienced the greatest VF worsening after failing to achieve their target IOP.
Target IOPs are typically chosen based on either the desired IOP reduction from baseline or by using fixed levels that are predetermined by the severity of the disease. These recommendations are fluid (no pun intended) and should be altered if further progression is noted despite achieving your target.
The key to success in setting target IOPs is to remind yourself (and your patients) that glaucoma is a disease of the optic nerve, and, while IOPs matter, it's the actual progression (or lack thereof) that is our primary concern.
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