Long-term intraocular pressure fluctuation and visual field progression in glaucoma patients with low intraocular pressure after post-trabeculectomy phacoemulsification

Background: The aim of this study was to evaluate the association of long-term intraocular pressure (IOP) fluctuation and visual field progression in glaucoma patients with low IOP after post-trabeculectomy phacoemulsification. Methods: A total of 688 eyes with primary open-angle glaucoma (POAG) and chronic primary angle-closure glaucoma (CPACG) were included in this study. The patients always had an IOP below 18 mmHg after post-trabeculectomy phacoemulsification. Visual field testing using the standard automated perimetry was periodically performed at 3 months and for at least 3 years postoperatively. The mean deviation on visual field was compared according to the standard deviation (SD) of the postoperative IOP (SD <= 2 mmHg group vs. SD > 2 mmHg group). Results: Preoperative and postoperative IOPs during the follow-up period did not differ significantly between the two study groups. Even though the mean deviations on visual field at postoperative 3 months were not different between the two groups, the mean deviations at the last follow-up were significantly worse in the postoperative IOP SD > 2 mmHg group than the postoperative IOP SD <= 2 mmHg group. Conclusions: Less postoperative IOP fluctuation was statistically associated with a slower progression of visual field damage in POAG and CPACG patients who kept low IOPs after the post-trabeculectomy phacoemulsification.