Eyeworld

AUG 2012

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

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64 EW RESIDENTS Los Angeles continued from page 63 cataract surgery when compared to cataract surgery alone. The iStent is a heparin-coated device that traverses the anterior chamber to Schlem's canal and is designed to augment physiologic drainage. There are very few pub- lished studies that have examined the iStent's long-term safety and long-term ability to achieve IOP control. This prospective, randomized, 2- year study looked at data collected from 239 patients randomized to two groups: 116 patients underwent iStent placement during cataract surgery and 123 control patients had routine cataract surgery without iStent placement. All patients in- cluded in the study were identified to have mild to moderate open- angle glaucoma (defined as patients with "visual field defects and/or characteristic optic nerve abnormali- ties consistent with mild to moder- ate glaucoma and cup-to-disc ratio not worse than 0.8"). All patients were subjected to a washout period from all glaucoma medications and were subsequently included in the study if untreated IOP was found to be between 22 and 36 mm Hg. Any patient who suffered a complication during cataract surgery was removed from analysis. As a follow-up to their 1-year results, the primary endpoint at 24 months was defined as ability to maintain IOP <21 mm Hg without the addition of ocular hypotensives. The secondary endpoint was the ability to lower IOP greater than 20% from baseline without the addi- tion of ocular hypotensives at 24 months. The results showed that 61% of patients who underwent placement of the iStent during cataract surgery had an IOP <21 mm Hg without ocular hypotensive med- ications as compared to 50% of pa- tients after cataract surgery alone at the end of 2 years. This difference was statistically significant (p value 0.036). There was also a trend toward the combination surgery achieving >20% reduction in IOP without medications, but these re- sults were not statistically significant (p value 0.09). The overall decrease in IOP from baseline was impressive in both groups. Cataract surgery alone resulted in a mean decrease in IOP of 7.5 mm Hg compared to 8.4 mm Hg in the iStent group. IOP in the iStent group remained stable between 12 and 24 months, while there was a slight increase (0.8 mm Hg) in IOP in the control group in the same time period. The rate of post-op complications was compara- ble between groups, and mostly related to cataract surgery; 2.6% of the iStents had to be repositioned and 4% required procedures to treat obstruction. The main conclusion of the study is that iStent placement in addition to cataract surgery is more effective than cataract surgery alone in the ability to lower IOP <21 with- out use of hypotensive medications. However, half of the control group met this goal with cataract surgery alone. In fact, the absolute extent of IOP reduction with cataract surgery alone in this study is quite impres- sive compared to larger studies. In the Ocular Hypertension Treatment Study, Mansberger et al, IOP lower- ing after cataract surgery was only 16.5%. In addition, the control group experienced a significant decrease in IOP from baseline (7.5 versus 8.4 mm Hg in control versus iStent groups, respectively). It is un- clear whether this 0.9 mm Hg mean difference in IOP reduction is clini- cally significant; in fact, there was no difference in visual field defects at 24 months between groups. August 2012

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