Eyeworld

EW RESIDENTS 63 patients may therefore be better identified with Slabaugh's definition of IOP spike. Slabaugh found that those who spiked were more likely to be men and to have eyes with longer axial lengths (25.08 mm versus 24.02 mm), greater anterior chamber depth (ACD), and wider gonioscopy angles. These characteristics were highly correlated; males had longer mean AL than females, and eyes with longer axial lengths had greater ACD and wider gonioscopy angle. The study also found that increased preoperative glaucoma medication use and prior laser trabeculoplasty increased the risk of a postoperative IOP spike. Of note, risk factors were identified by using a nominally significant level of 0.05 without correction for multiple comparisons. Kim et al. also found the inci- dence of IOP elevation after cataract surgery to be higher in those eyes with longer axial lengths. 10 Kim's study, however, defined IOP eleva- tion as IOP greater than 23 mmHg on postoperative day one, and the patient population was not limited to glaucoma patients—only 5.7% (63 of 1,111) of patients studied had glaucoma. Though Kim's study was based on resident surgeons and Slabaugh's study was based on one surgeon's outcomes, the two studies corroborated with each other. Slabaugh hypothesized that the biomechanical differences in longer eyes make them less able to accom- modate the stressors of cataract surgery. Another possibility is that larger eyes with larger ACDs require more viscoelastic material to fill the eye, thus making it harder to com- pletely remove. Unlike previous studies, 10,11 Slabaugh did not find preoperative baseline IOP as a risk factor for IOP spikes likely because the IOP spike was defined as a per- cent change from baseline IOP. The only postoperative pressure lowering medication used that was mentioned in Slabaugh's study was oral acetazolamide. It was given as part of routine postoperative care (500 mg six hours after surgery and the following morning); however, there were various reasons for pa- tients not taking it, such as allergies or failure to fill the prescription. Since this study was a retrospective study, the authors could not control for the use of acetazolamide, but they did find that it was fairly effec- tive in preventing IOP spikes. It did not seem like patients were given any glaucoma pressure-lowering drops immediately after surgery. It is conceivable that these glaucoma patients were spiking post surgically simply because of a one-day hiatus from their usual glaucoma drops while their operated eye was patched. The clinically relevant question is who do we need to prophylacti- cally treat perioperatively? Studies are needed to determine which pa- tient population would suffer long- term clinical consequence from IOP spikes. Glaucoma patients have higher risk of IOP spikes, but up to 8.1% of non-glaucomatous eyes also exhibit IOP spikes. 5 It is not wise to simply treat everyone prophylacti- cally as postoperative hypotony (IOP <5 mmHg) can occur in up to 6.1% of patients. 5 Furthermore, lower IOPs were associated with less tightly sealed cataract wounds, so surgeons should not unnecessarily lower IOPs. 12 Further studies are required to determine what type of postoperative IOP elevation (percent IOP increase versus IOP threshold versus absolute IOP increase) is most able to identify those at risk for long-term damage. It would be inter- esting to know if Slabaugh's results would be similar had an IOP spike been defined differently. Slabaugh's study took an in- depth look at a number of variables and identified certain characteristics in patients whom the surgeon should monitor more closely and carefully postoperatively. Glaucoma patients with longer axial lengths, deeper anterior chambers and wider gonioscopy angles, who had past laser trabeculoplasty, and who are on a higher number of glaucoma medications preoperatively could benefit from prophylactic pressure lowering therapy perioperatively. Oral acetazolamide is one option but perhaps topical agents may be equally effective. EW References 1. Friedman DS et al. Surgical strategies for coexisting glaucoma and cataract: an evidence-based update. OPHTHA 109, 1902–1913 (2002). 2. Mathalone N et al. Long-term intraocular pressure control after clear corneal pha- coemulsification in glaucoma patients. Journal of Cataract & Refractive Surgery 31, 479–483 (2005). 3. Gross JG, Meyer DR, Robin AL, Filar AA, and Kelley JS. Increased intraocular pressure in the immediate postoperative period after extracapsular cataract extraction. AJOPHT 105, 466–469 (1988). 4. Fang EN and Kass MA. Increased intraocular pressure after cataract surgery. Semin Ophthalmol 9, 235–242 (1994). 5. Shingleton B, Rosenberg R, Teixeira R, O'Donoghue MW. Evaluation of intraocular pressure in the immediate postoperative period after phacoemulsification. Journal of Cataract & Refractive Surgery, 1953–1957 (2007). 6. Levkovitch-Verbin H et al. Intraocular pressure elevation within the first 24 hours after cataract surgery in patients with glaucoma or exfoliation syndrome. Ophthalmology 115, 104–108 (2008). 7. Kohnen T, von Ehr M, Schütte E, and Koch DD. Evaluation of intraocular pressure with Healon and Healon GV in sutureless cataract surgery with foldable lens implantation. Journal of Cataract & Refractive Surgery 22, 227–237 (1996). 8. Cekiç O and Batman C. Effect of capsu- lorhexis size on postoperative intraocular pressure. Journal of Cataract & Refractive Surgery 25, 416–419 (1999). 9. Slabaugh MA, Bojikian KD, Moore DB, and Chen PP. Risk factors for acute postopera- tive intraocular pressure elevation after phacoemulsification in glaucoma patients. Journal of Cataract & Refractive Surgery (2014).doi:10.1016/j.jcrs.2013.08.048. 10. Kim JY et al. Increased intraocular pressure on the first postoperative day following resident-performed cataract surgery. Eye 25, 929–936 (2011). 11. O'Brien P, Ho S, Fitzpatrick P, and Power W. Risk factors for a postoperative intraocular pressure spike after phacoemulsi- fication. Canadian Journal of Ophthalmology, 51–55 (2007). 12. Taban M et al. Dynamic morphology of sutureless cataract wounds—effect of incision angle and location. Survey of Ophthalmology 49 Suppl 2, S62–72 (2004). Contact information Srikumaran: dsrikum1@jhmi.edu Wang: awang34@jhmi.edu intraocular pressure patients" April 2014

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