NOV 2012

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

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November 2012 February 2011 EW GLAUCOMA Anticipating IOP elevation after anterior segment procedures by Tony Realini, M.D. E levated IOP is a common occurrence following many ocular procedures, from refractive surgery to cataract extraction to vitre- oretinal procedures. In many cases, the magnitude of the IOP rise is clin- ically insignificant. In others, IOP can rise to levels that may pose a threat to the optic nerve or the posterior segment's vascular supply. Knowing when to expect IOP spikes, and who is at particular risk, can be helpful in assisting perioperative planning, particularly in patients with pre-existing glaucoma who may be most at risk for IOP-related complications. At the 2012 Associa- tion for Research in Vision and Ophthalmology [ARVO] meeting, several investigative teams reported the prevalence and risk factors for elevated IOP following common anterior segment procedures. Cataract surgery "Cataract surgery often results in a long-term lowering effect on IOP," said Daniel Moore, M.D., University of Washington, Seattle. "In the immediate post-operative period, however, IOP may be acutely elevated due to retained viscoelastic devices, intraocular inflammation, or other factors." He and colleagues conducted a retrospective case series of 209 eyes of 209 patients with various forms of glaucoma (the majority of which were primary open-angle glaucoma) who underwent phacoemulsifica- tion. All glaucoma patients routinely received 250-500 mg of oral acetazo- lamide 6 hours after and the morn- ing after surgery. The goal of this study was to identify the frequency of and risk factors for IOP spikes of 10 mm Hg or greater (compared to average IOP at the three immedi- ately pre-op clinic visits) observed on post-op day 1. Despite prophylaxis with an oral carbonic anhydrase inhibitor, 35 eyes (17%) manifested an IOP spike of 10 mm Hg or greater on the first post-op day, he said. "Thirty-four of the 35 patients regained IOP control with additional medications, but one patient required trabeculectomy during the post-operative period." Several easily identifiable factors predicted which patients were most susceptible to an IOP spike. "These included patients who were younger, Intervention for IOP management No change in drops Decreasing steroids, Switching to lower potency steroids or adding a single glaucoma agent Above with 2 glaucoma agents 3 or more glaucoma agents MMT + surgery Total number of patients with IOP spike (>24) The table shows the intervention methods for patients with IOP >24 in Dr. Kirkland's study Source: Wendy Kirkland, M.D. males, those with wide angles on pre-operative gonioscopy, those with a longer axial length, and those who had previously undergone laser trabeculoplasty," Dr. Moore said. In addition, perhaps not surpris- ingly, the patients who elected not to take their acetazolamide tablets also were at higher risk for an IOP spike. Several potential factors were found not to be associated with the risk of an IOP spike. These included ethnicity, type of glaucoma, and severity of glaucoma, he said. "Addi- tionally, no significant difference between the two groups was found with wound placement, intraopera- tive maneuvers and complications, intraocular lens type, or placement of a wound suture at the conclusion of the case." DSAEK surgery Descemet's stripping automated endothelial keratoplasty (DSAEK) can also be associated with IOP elevation, although in this case the IOP rise can be more chronic than acute and may be largely attributa- ble to long-term topical steroid use following this procedure. "DSAEK is a partial thickness corneal transplant technique that is increasingly being performed for corneal endothelial dysfunction in lieu of penetrating keratoplasty," said Wendy Kirkland, M.D., Georgetown University, Washington, D.C. To evaluate the frequency of IOP elevation after DSAEK (defined as IOP greater than 24 mm Hg), she and colleagues conducted a retro- spective case series of 222 patients undergoing the procedure most commonly for Fuchs' endothelial dystrophy or pseudophakic bullous keratopathy, of whom approxi- mately one-third had pre-existing glaucoma. "Post-operatively, 29.7% of all patients developed an IOP eleva- tion," said Dr. Kirkland. The timing of the IOP elevation was quite variable, with some manifesting on post-op day 1 and others as late as 8-13 months after surgery. "The highest prevalence of patients with glaucoma was 16.3% occurring during months 2 through 4." Patients with pre-existing glau- coma were statistically significantly more likely to have uncontrolled IOP at any point during follow-up than patients without glaucoma (48.6% versus 21.1%, respectively, p<0.0001). Peripheral anterior synechiae (PAS) formation was also predictive of IOP elevation, she said. "Overall, 12.6% of patients were noted to have gross PAS post-operatively, and nearly two-thirds of these patients needed more aggressive IOP management during the course of follow-up." Approximately one-third of patients with IOP elevations were adequately controlled by either re- ducing the steroid dosage or adding a single IOP-lowering medication, she said. Another 44% were con- trolled by the addition of two or three IOP-lowering medications. "Twelve patients (18%) required maximal medical therapy or surgery," she added. Clinical implications Not all IOP elevations pose a threat to ocular health, and most eyes can tolerate short-term elevations with- out harm. There is clinical value in identifying the patients most likely to develop an IOP spike, and also those patients most likely to be harmed by one. "Although the clinical implica- tion of a short-term IOP spike has not been clearly defined," said Dr. Moore, "elevated IOP remains a primary risk factor for glaucoma progression." Dr. Kirkland agreed. "Our study suggests careful monitoring of IOP after DSAEK, particularly in patients with pre-existing glaucoma or complicated surgical histories." EW Editors' note: Drs. Kirkland and Moore have no financial interests related to this article. Contact information Kirkland: wkirklandmd@gmail.com Moore: daniel.b.moore@duke.edu 14 (21.2) 15 (22.7) 12 (18.2) 66 (100) 57 3 (4.5 ) 22 (33.3)

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