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EW RESIDENTS 62 April 2014 by Aaron S. Wang, MD, PhD, resident, and Divya Srikumaran, MD, program director, Wilmer Eye Institute, Johns Hopkins University, Baltimore Review of "Risk factors for acute postoperative elevation after phacoemulsification in glaucoma C ataract surgery often has a beneficial long-term low- ering effect on intraocular pressure (IOP) for glauco- matous eyes. 1,2 There is, however, also a risk of early postop- erative IOP elevation. Various explanations for IOP elevation after phacoemulsification include residual viscoelastic materials, trabecular meshwork trauma, and trabecular meshwork obstruction with cortical material or hyphema. Post-surgical IOP spikes can result in complica- tions such as ocular pain, corneal edema, delayed wound healing, central retinal artery occlusion, and optic nerve damage. 3,4 There are no standard guidelines describing which patients should receive pro- phylaxis IOP-lowering therapy, nor guidelines to identify eyes at increased risk for IOP spikes. The majority of studies on post- operative IOP elevations looked at the prevalence of IOP spikes in normal and glaucomatous eyes, the time frame during which such eleva- tion occurs, and the effectiveness of different medical and surgical strate- gies to reduce the risk of spikes. Shingleton et al. found that 8.1% (21 of 258) of normal eyes and 15.6% (5 of 32) of glaucomatous eyes had IOP higher than 30 mmHg at day one postoperatively. 5 Levkovitch-Verbin et al. found that most IOP elevation occurred at 4 hours postoperatively, and IOP >25 mmHg did not occur among normal eyes, IOP >5 mmHg and >30 mmHg occurred in 55% and 28% of glau- coma patients, respectively, and 27% and 11% of exfoliation syndrome patients, respectively. This same study found that instillation of tim- olol maleate 0.5% at the end of sur- gery eliminated IOP >30 mmHg in all groups 4 hours postoperatively. 6 Other studies have indicated that a larger capsulorhexis size and the use of higher viscosity viscoelastic mate- rial are risk factors for IOP elevations and that specific viscoelastic re- moval techniques may reduce the incidence of high IOP. 7,8 To date, only a few studies have investigated patient characteristics that are risk factors for postoperative IOP elevations. Slabaugh et al. re- cently published in the Journal of Cataract & Refractive Surgery a retro- spective case series of 271 glaucoma patients who underwent pha- coemulsification at the University of Washington over a 16-year period. 9 The diagnosis of glaucoma was established by characteristic optic nerve changes and/or visual field loss, not IOP. Patients were excluded if they had previous incisional glau- coma surgery. The authors analyzed many characteristics, including demographics, glaucoma type, cor- rected visual acuity, visual field loss, mean preoperative IOP, preoperative glaucoma medications, and ocular dimensions (axial length, anterior chamber depth, central corneal thickness). A spike was defined as IOP 50% greater at one day postoperatively than the baseline preoperative IOP. The baseline IOP was defined as the mean IOP from three preceding clinic visits. This definition of an IOP spike differed from the usual definition found in similar types of studies, which regarded a spike as IOP greater than a threshold IOP (usually 25 or 30 mmHg). Curiously, Slabaugh and Shingleton were in close agreement with the percentage of glaucoma patients (17% versus 15.6%, respectively) who had pres- sure spikes one day postoperatively, despite different definitions of IOP spikes. 5,9 Percentage change does seem more appropriate for the glau- coma population because treatment goals for glaucoma are often defined as percentage changes from baseline, and glaucoma patients may be sus- ceptible to optic nerve damage at much lower pressure than the preset threshold IOP. Advanced glaucoma Aaron S. Wang, MD, PhD It would be valuable to know which glaucoma patients are most at risk for IOP spikes after phaco. This month, I asked the Wilmer Eye Institute to review this new study that analyzes this question. –David F. Chang, MD, chief medical editor Divya Srikumaran MD, program director, Wilmer Eye Institute, Johns Hopkins University Risk factors for acute postoperative intraocular pressure elevation after phacoemulsification in glaucoma patients Mark A. Slabaugh, MD, Karine D. Bojikian, MD, Daniel B. Moore, MD, Philip P. Chen, MD J Cataract Refract Surg (April) 2014; 40: 538–544 Purpose: To evaluate the risk factors for and frequency of an acute intraocular pressure (IOP) elevation (spike) after phacoemulsification in patients with glaucoma. Setting: Academic glaucoma clinics and operating rooms. Design: Retrospective case series. Methods: Charts of consecutive glaucoma patients without prior incisional glaucoma surgery undergoing phacoemulsification by a single surgeon between August 1996 and July 2012 were reviewed to obtain demographic information, preoperative glaucoma medications, severity and treatment measures, intraoperative course and postoperative outcomes. A postoperative IOP spike was defined as IOP greater than 50% above baseline IOP. Main outcome measures were the number of eyes with postoperative IOP spike, and risk factors associated with IOP spike after phacoemulsification. Results: Of 271 eyes (271 patients) included in the study, 45 (17%) had an IOP spike. Risk factors for postoperative IOP spike by multivariate analysis included longer axial length or associated characteristics (wider angle grade on gonioscopy, deeper anterior chamber, and male sex), higher number of preoperative IOP lowering medications, prior laser trabeculo- plasty, and lack of postoperative oral acetazolamide. One eye (0.4%) required trabeculectomy during the 90-day postoperative period. Conclusion: A significant proportion of glaucoma patients undergoing phacoemulsification experience an IOP spike. Patients requiring a higher number of IOP lowering medications or laser trabeculoplasty for IOP control preoperatively as well as those with greater axial length should be treated more aggressively with IOP lowering medication in the immediate postoperative period. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned. EyeWorld journal club

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