EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/387844
EW RESIDENTS 106 October 2014 by Akshay Thomas, MD, Nisha Nagarkatti-Gude, MD, Daniel Lattin, MD, David Simons, MD, PhD, Rasanamar Sandhu, MD, MPH, Beth Edmunds, MD, PhD, Andreas K. Lauer, MD, Casey Eye Institute Cataract surgery to lower IOP in narrow angle and chronic angle closure glaucoma The effect of phaco on IOP in eyes with narrow angles or chronic angle closure glaucoma is a special situation. This month, I asked the Oregon Health & Science University Casey Eye Institute residents to review this multicenter study that analyzed this situation. –David F. Chang, MD, chief medical editor T he intraocular pressure (IOP)-lowering effect of cataract surgery in both glaucomatous and non-glaucomatous eyes has been documented in numerous stud- ies dating back to the mid-1990s. 1 In a retrospective case series of patients titled "Cataract surgery reduces intraocular pressure in patients with narrow angles and chronic angle closure glaucoma," published in the Journal of Cataract & Refractive Surgery, Brown and colleagues describe the impact of cataract surgery in chronic angle closure glaucoma (CACG) or patients with narrow angles. They also identify preoperative parameters such as preoperative IOP, anterior chamber depth (ACD), and axial length (AL) that influence the magnitude of IOP reduction. This single-center case series from the private practice of the lead author included 83 eyes of 56 patients with a history of CACG or narrow angles that subsequently un- derwent cataract surgery. All patients in the study previously underwent laser peripheral iridotomy in the study eye, and patients were exclud- ed if they had undergone any other intraocular surgery. Demographic information, preop AL, preop ACD, pre- and postop IOP, and number of glaucoma medications used pre- and postop were recorded. The preop IOP was defined as the average of measurements recorded by Goldmann applanation tonom- etry in the 2 visits prior to cataract surgery. Patients were stratified into 4 groups based on preoperative IOP: IOP >20 mmHg, 18< IOP ≤20 mmHg, 15< IOP ≤18 mmHg, and IOP ≤15 mmHg. The postoperative IOP was defined as the average of the last 3 IOP measurements in the patients' charts. Ordinary least- squares linear regression was used to correlate change in IOP as a func- tion of preoperative IOP, ACD, and AL. The patients were followed for a mean 3±2.3 years (range 0.5 to 10.0 years). Brown et al. found a mean IOP reduction of 3.28 mmHg (18%) in their group of patients, with 88% of patients having a decrease in IOP. The greatest magnitude of IOP reduction of 5.3 mmHg was found in the group with the highest preop IOP. IOP reduction was less pronounced for subsequent groups (4.6, 2.5, 1.4 mmHg, respectively). The mean percentage of IOP reduc- tion was greatest in the group with the highest preoperative IOP and was lowest in the group with the lowest preoperative IOP. The authors also found that 100% of the 2 high- est preoperative IOP groups had a reduction in IOP following cataract surgery compared to 96% and 59% of patients in the third and fourth groups, respectively. The authors clearly demonstrate that preopera- tive IOP correlates with change in IOP after cataract surgery in their group of patients. Additionally, they report that the IOP-lowering effects of cataract surgery were sustained for a mean of 3±2.3 years (range 0.5 to 10.0 years). The standard devi- ation for follow-up in this series is large and the range is broad and therefore qualifies the assertion of sustainability after the intervention. The authors also found that shallow - er preoperative ACD was associated with a greater IOP decrease after cataract surgery (r=0.27, P=0.027). These findings are consistent with earlier studies in which a larger magnitude of IOP reduction following cataract surgery was seen in eyes with normal tension glau- coma (NTG), primary open angle glaucoma (POAG) ocular hyperten- sion whose preoperative ACD were shallower. 2–4 The authors found that 18% of patients required fewer glaucoma medications following cataract surgery. The authors did not find that preoperative AL correlated with IOP change following cataract surgery. This single center study provides useful information about the effect of cataract surgery on IOP lowering in a group of patients infrequently studied for this purpose. Previously published data suggests that patients with angle closure glaucoma appear to have a larger reduction in IOP fol- lowing cataract surgery compared to those with open angle glaucoma. 5,6 Brown et al. used methodology reminiscent to a recently published study where Mansberger et al. 7 retrospectively analyzed 63 eyes from the control group of the Ocular Hypertension Treatment Study (OHTS) that underwent cataract surgery over the course of the trial. These eyes were compared to 743 similar controls that did not undergo cataract surgery. A significant reduction in IOP of Andreas K. Lauer, MD Casey Eye Institute ophthalmology residents, from left to right: Laura Kopplin, MD, PhD, Daniel Lattin, MD, Akshay Thomas, MD, Dong-Wouk Park, MD, Fran Wu, MD, Anthony Grillo, MD, Grant Aaker, MD, Nisha Nagarkatti-Gude, MD, Griffin Ja dine, MD, Erin Boese, MD, Bryce Radmall, MD, Hillary Stiefel, MD, David Simons, MD, PhD, Rasanamar Sandhu, MD, MPH, and Andreas K. Lauer, MD Source: Casey Eye Institute EyeWorld journal club Beth Edmunds, MD, PhD