Eyeworld

MAY 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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56 EW RESIDENTS May 2012 EyeWorld journal club Wills Eye Institute residents' review of intraocular pressure using phakic by Matthew Dykhuizen, M.D., Mila Heersink, M.D., Laura Heinmiller, M.D., Teri Kleinberg, M.D., and Tara Uhler, M.D. Tara Uhler, M.D. Director, Resident Education Wills Eye Institute, Philadelphia This month, the Wills residents reviewed a very important paper on the effect of phaco on IOP, which concur- rently appears in this month's Journal of Cataract & Refractive Surgery. —David F. Chang, M.D., chief medical editor P hacoemulsification is one of the most commonly performed ophthalmo- logic procedures; glau- coma is one of the most prevalent ocular diseases and a major cause of visual impairment worldwide. Several long-term stud- ies, clinical case series, and meta- analyses have suggested that phacoemulsification decreases IOP in patients with angle-closure and open-angle glaucoma (Friedman 2002; Lam 2008; Nonaka 2005, 2006; Poley 2009; Shrivastava 2010). However, the magnitude of IOP-low- ering effect in patients with open- angle glaucoma and ocular hyper- tension is still controversial. We applaud the efforts of Chang et al (2012) to help answer this important clinical question. The authors present a retrospec- tive, comparative case series evaluating the long-term effect of phacoemulsification on IOP in 29 patients with ocular hypertension or open-angle glaucoma followed for 3 years and using the unoperated, fel- low eye as the control. Complete 3- year follow-up data was available for 17 of the 29 subjects. No statistically significant difference in IOP be- tween operated and fellow eye was identified at any study time point (pre-op: N=29, P=0.98; week 1: N=23, P=0.76; month 4.5: N=25, P=0.06; year 1: N=25, P=0.67; year 2: N=19, P=0.37; year 3: N=17, P=1.00). There was no statistically significant difference in the mean number of IOP-lowering medications between surgical and fellow eyes either pre- or post-op (pre-op: surgical 2.13±1.13, fellow 1.90±1.23, P=0.76; post-op at mean follow-up of 27.7 Long-term effect of phacoemulsification on intraocular pressure using phakic fellow eye as control Ta C. Chang, M.D., Donald L. Budenz, M.D., M.P.H., Anthony Liu, M.D., Won I. Kim, M.D., Tam Dang, M.D., Chan Li, M.D., Andrew G. Iwach, M.D., Sunita Radhakrishnan, M.D., Kuldev Singh, M.D., M.P.H. J Cataract Refract Surg (May) 2012; 38:866-870. Purpose: To investigate the long-term effect of phacoemulsification on IOP in patients with ocular hypertension and open-angle glaucoma. Setting: Three multispecialty ophthalmology practices and one glaucoma specialty group. Design: Retrospective comparative case series. Methods: Review of medical records of patients with open-angle glaucoma or ocular hypertension who had had unilateral phacoemulsification (without prior or concurrent ophthalmic procedure) with the fellow eye remaining phakic at least 3 years post-operatively. Results: Pre-operatively, the IOP in the surgical and fellow eyes in the 29 patients was 15.66 mm Hg±3.33 (SD) and 15.64±4.24 mm Hg (P=.98), respec- tively. Post-operatively, it was 13.56±2.04 mm Hg and 14.92±2.85 mm Hg, respectively, at 4.5 months (P=.06); 14.88±3.20 mm Hg and 15.27±3.19 mm Hg, respectively, at 1 year (P=.67); 14.16±2.61 mm Hg and 14.95±2.79 mm Hg, respectively, at 2 years (P=.37); and 14.68±3.44 mm Hg and 14.68±2.68 mm Hg at 3 years (P=1.00), respectively. There was no significant difference in the mean number of IOP-lowering medications used in the surgical (1.96±1.40) and fellow eyes (2.08±1.44) post-operatively (P=.77). Conclusions: In a cohort of ocular hypertensive and glaucoma patients, uncomplicated phacoemulsification had no significant IOP-lowering effect compared with the phakic fellow eye for up to 3 years post-operatively. There was also no difference between the mean number of post-operative IOP- lowering medications used in the surgical and fellow eyes. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned. Front row (left to right): Michael Tibbetts, M.D.; Sonya Shah, M.D.; Teri Kleinberg, M.D.; Fatima Ahmad, M.D.; Laura Heinmiller, M.D.; Sarah Driscoll, M.D.; Kristina Pao, M.D.; Kristin DiDomenico, M.D.; Anthony Farah, M.D. Back row (left to right): Brandon Johnson, M.D.; David Lally, M.D.; Mila Heersink, M.D.; Dave Perlmutter, M.D.; Tim Johnson, M.D.; Vik Setlur, M.D.; Jared Peterson, M.D.; Doug Wisner, M.D.; Ali Khan, M.D.; Dave Salz, M.D.; Matt Dykhuizen, M.D.; Chris Brady, M.D. Missing: Andy Batchelet, M.D.; Amanda Matthews, M.D.; Adi Smith, M.D. months: surgical 1.96±1.40, fellow 2.08±1.44, P=0.77). The authors' use of the fellow eye as a control to evaluate the IOP- lowering effect of phacoemulsifica- tion is laudable and is the first reported study to do so. Coupled with the retrospective design, this caused inherent limitations related to patient selection and sample size, clinical definitions, missing data, and length of follow-up. The small sample size is the major limitation and a direct result of the strict inclu- sion criteria (ocular hypertension or open-angle glaucoma and uncompli- cated phacoemulsification in one eye with fellow eye remaining pha- kic for at least 3 years post-op). The authors enrolled from four different sites and reported great difficulty in finding patients who fulfilled inclu- sion criteria. In particular, it is uncommon for patients to remain phakic in the fellow eye 3 years after cataract extraction without underly- ing pathology causing asymmetric cataract formation. Of 1,683 medical records identified by ICD-9 and CPT codes, 29 (1.72%) could be included. The authors employed strict exclu- sion criteria (history of trauma to ei- ther eye, secondary causes of ocular hypertension or glaucoma, and nar- row angles on exam). However, as they acknowledged, the treated eye may have had underlying pathology that was unrecognized or undocu- mented or could not be discerned from record review. It would be interesting to know the time frame of this study, which included both scleral-tunnel and clear-corneal techniques. The differ- ent approaches may reflect advances in surgical technique over many years or surgeon preferences at dif- ferent sites and may have influenced the results. Additionally, a table of the raw data for the 29 subjects would have been useful to identify outliers and further evaluate IOP variability and ranges. Study subjects were selected using ICD-9 codes and not clearly defined with respect to clinical defi- nitions of ocular hypertension and open-angle glaucoma. Also, as the authors noted, documentation of gonioscopic findings or data regard- ing anterior chamber depth was un- available for the majority of patients. Without strict definitions and clear documentation, it is diffi- cult to determine the exact pathol- ogy of the study population and therefore the clinical application of the results. However, given the low mean pre-op IOP as well as the mini- mal difference in medications or need for previous or subsequent glaucoma interventions in either the treated or control eye, the subjects most likely had early glaucoma or borderline ocular hypertension. The effect of intervention on IOP is pro- portional to starting IOP. With lower pre-op IOP, the effect of phacoemul- sification would be expected to be small, and differences would be especially difficult to detect with a small sample size.

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