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Mark S. Hansen, Kelly W. Muir, Henry Tseng, Anthony N. Kuo, Pratap Challa, Cecile Santiago-Turla, Alice Ventura, Molly M. Walsh; Pilot Study: The Impact Of Advanced Glaucoma On Changes In Aqueous Outflow After Cataract Surgery. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1992.
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Prior studies have provided evidence for a decrease in intraocular pressure after cataract surgery in patients with advanced glaucoma. Some have proposed cataract extraction as a potential therapy in glaucoma to decrease the intraocular pressure. We hypothesized that the intraocular pressure decreases as a result of increased aqueous outflow. In this study, we measured aqueous outflow facility using tonography before and after cataract surgery in patients with advanced glaucoma and compared them to normal controls. Tonography was established to measure the patency of the pathway of aqueous humor flow and determine if changes in intraocular pressure are due to change in facility of outflow or a change in the net rate of aqueous humor formation.
Tonography was perfomed by a skilled technician on 6 end-stage glaucoma patients and 6 control patients both preoperatively and postoperatively (90 days after surgery). The patient was placed in a comfortable, supine position and the tonometer was cleaned and calibrated. Proparacaine was placed in the appropriate eye prior to tonography measurements. The patient was accustomed to the probe with 3 short trials prior to the beginning of the recorded test. Tonography was recorded for at least 4 minutes using the appropriate tonometer weights according to the initial intraocular pressure recording. After tonography measurements were performed, the Po/C ratios were calculated. A student t-test was performed to determine whether or not the difference between the 2 groups were statistically significant.
The initial results from our pilot study revealed that end-stage glaucoma patients (minus one) had an increase in the Po/C ratios after the surgery, whereas all control patients had a decrease in the Po/C ratio.
Contrary to our hypothesis, the increase in Po/C ratio in the end-stage glaucoma patients indicates a decrease in aqueous outflow after surgery. This is a significant consideration in management decisions with regards to patients with glaucoma. Further studies are warranted to determine whether or not these trends maintain statistical significance with a larger sample size.
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