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Editors Selection IGR 8-3

Surgery: Cataract extraction after GDD

Comment by Tarek Shaarawy on:

14072 Effect of temporal clear corneal phacoemulsification on intraocular pressure in eyes with prior Ahmed glaucoma valve insertion, Sa HS; Kee C, Journal of Cataract and Refractive Surgery, 2006; 32: 1011-1014

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The effect of phacoemulsification on IOP in eyes with prior Glaucoma Drainage Devices was investigated in two studies. Sa and Kee (916) report that mean IOP immediately before phacoemulsification was not significantly different from the mean IOP at any follow-up point. Although the changes were not significant, mean IOP 1 month after phacoemulsification increased by 4 mmHg or more in 6 patients (46.2%), and 1 of them had an IOP spike of 10 mmHg. The number of glaucoma medications prescribed after phacoemulsification was significantly greater than that before phacoemulsification in eyes with prior Ahmed glaucoma valve insertion. After phacoemulsification 6 patients (46.2%), who had not required medication before phacoemulsification, subsequently required 1 or 2 glaucoma medications for IOP control. Five of these 6 patients needed glaucoma medication approximately 1 month after phacoemulsification, and 1 patient needed medication at 5 months. All eyes with additional glaucoma medication continued to require the same number of medications.

Erie et al. (944), also reported that the mean IOP did not significantly change at 1st month, 1 year and the last follow-up. What was interesting, though, was that the mean number of glaucoma medications used did not change, in contrast with the previous study.

The answer might be found in patients' demographics. The first paper included 78% neovascular glaucoma, and 22% uveitic glaucoma patients. While the second paper had a total of 25% for both neovascular and glaucoma patients, and 75% multiple other pathologies, notably juvenile glaucoma and PEX glaucoma. It is conceivable, as Ho-Seok and Changwon mention, that postoperative fibroblastic activity secondary to phacoemulsification, could access the subconjunctival space through tubular flow, especially in uveitic and neovascular cases, where the blood-aqueous barrier is already destabilized. Perhaps a good take home message here would be that although results of IOP control in post-phacoemulsification |in patients with GDDs are acceptable, special attention should be given to certain pathological subgroups that might be associated with a higher risk of loss of IOP control. This of course has to be validated by further studies. And in light of the relatively few numbers cases available to studies in such specific situations, this should encourage multi-centric and multinational collaboration.

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