Purpose: To evaluate the relationship between intraocular pressure (IOP) and the rate of visual field (VF) progression in treated glaucoma.
Methods: In a clinic-based, retrospective study, data of consecutive primary open-angle and angle-closure glaucoma patients with ≥ 5 VFs between 1989 and 2008 were analyzed. The Guided Progression Analysis software, which provides the rate of change of Visual Field Index per year, was used to assess the rate of progression (ROP). IOP measurements during the VF examination visits were extracted, and mean, peak, and fluctuation (SD) of IOP during the follow-up were calculated. Relationships between IOP parameters and ROP were analyzed using regression models. Other risk factors evaluated were age, sex, type of glaucoma, presence of hypertension and diabetes, severity of VF loss at presentation, glaucoma surgery during follow-up, number of antiglaucoma medications, and follow-up duration.
Results: During the study period, 296 eyes of 213 glaucoma patients had undergone ≥ 5 VFs. IOP fluctuation was the only IOP parameter significantly associated with ROP (β=-0.37, P=0.02). Evaluated in a multivariate model with other risk factors, the severity of VF damage at presentation (β=0.08, P=0.002) and IOP fluctuation (β=-0.35, P=0.02) remained significantly associated with ROP. Greater IOP fluctuation was seen in eyes undergoing glaucoma surgery and eyes requiring more antiglaucoma medications during follow-up.
Conclusions: Long-term IOP fluctuation was the most important IOP parameter associated with increased ROP of glaucomatous VF loss. This association is likely due to the confounding effect of enhanced therapy in eyes suspected to be progressing.