Cataract Surgery and Intraocular Pressure (IOP)
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PURPOSE: The effect of cataract surgery on IOP in patients with glaucoma is not well understood. We sought to analyze fluctuations in IOP in controls, glaucoma suspects, and patients with mild, moderate, and severe primary open angle glaucoma (POAG) undergoing cataract surgery in a well-diversified population. METHODS: In an IRB-approved retrospective study, 236 controls (Group A), 37 glaucoma suspects (Group B), and 96 patients with POAG (mild, moderate, severe; Groups C-E) were recruited. One eye was randomly selected per patient. Exclusion criteria included: <18 years, secondary glaucoma, one functional eye, or follow-up <3 months. Data collected included age, race, gender, glaucoma family history, CCT, axial length (AXL), anterior chamber depth (ACD), lens thickness (LT), IOP, and visual acuity (VA). Post-operative IOP and VA were determined at several intervals. Linear trends over groups A-E were made with a Jonckheere-Terpstra test. χ2 analyses were used to evaluate differences between groups A-E. Wilcoxon Rank-Sum test was used to evaluate postoperative changes. Multiple linear regression was used to evaluate predictors of IOP change at 1 year. RESULTS: IOP reduction at 1 year in groups A-E were 8.6%, 8.1%, 10.8%, 18.3%, and 9.1%, respectively. Medications at 1 year did not change significantly. In POAG eyes, higher pre-op IOP and more medications were predictive of a higher reduction in IOP at 1 year (β= -0.62, -1.60; p<0.05). In control eyes, higher pre-op IOP and higher CCT were predictive of more IOP reduction at 1 year (β= -0.53, -0.02; p<0.05). DISCUSSION: In this population, all groups showed reduction of IOP after cataract surgery. Among the glaucoma groups, severe glaucoma patients had the lowest reduction of IOP (9.1%), most probably due to reduced outflow facility. However, the medication load stayed unchanged in all groups. In the control group, pre-op IOP and thicker CCT determined post-op IOP reduction. CONCLUSION: IOP reduction one year after cataract surgery in glaucomatous eyes is dependent on higher pre-op IOP and increased glaucoma medications. In non-glaucomatous eyes, higher pre-op IOP and thick CCT determine the degree of post-operative IOP reduction.