Device shows promise for glaucoma surgery

September 1, 2008

A miniature shunt (Ex-Press, Optonol) is as effective as standard trabeculectomy procedures in the lowering of IOP in patients with glaucoma, according to a retrospective review. The advantages of implementation of the device over standard trabeculectomy include a greater decrease in the postoperative medications taken by patients, lower levels of hypotony occurrence, and a predictable, even flow reduction of aqueous fluid from the subconjunctival space.

Key Points

Patients who received the novel intraocular implant demonstrated lower rates of hypotony and required fewer medications to control their IOP postoperatively compared with those who were treated with standard trabeculectomy, making the device a viable option in treating IOP in patients with glaucoma.

Lionel Marzette, MD, a research fellow at the Department of Ophthalmology, Duke University Eye Center, Durham, NC, conducted a retrospective review comparing the success and complication rates in patients with glaucoma who received either the shunt (76 eyes of 69 patients) or a conventional trabeculectomy (77 eyes of 65 patients) to lower their IOP. All surgeries were performed by Leon W. Herndon, MD, the principal investigator of the study.

IOP reduction

Results showed that 78% of the patients who received the shunt and 68% who received standard trabeculectomy treatment had a successful treatment in reducing IOP. Data showed that 90% and 81% of the shunt and standard trabeculectomy groups, respectively, had a reduction in preoperative to postoperative medications. Postoperatively, the shunt group had an overall greater reduction in IOP (50.9%) when compared with the standard trabeculectomy group (44.6%). Dr. Marzette said that this value did not reach statistical significance, however. Overall, the procedure was ineffective because of hypotony in six (8%) patients who received the implant and 14 (21%) patients who underwent standard trabeculectomy.

"The [shunt] group did show a statistically significant small but still greater reduction in the medications from the preoperative to postoperative period, showing an 87% reduction where the standard trabeculectomy group had an 81% reduction in the number of medications required," Dr. Marzette said.

The device is a non-valved, stainless steel glaucoma shunt, designed to lower IOP, that is implanted into the aqueous chamber and drains into the subconjunctival space. It has a lumen of either 50 or 200 µm, is approximately 0.5 mm in length, and is much smaller than conventional glaucoma drainage devices.

Implanting the device

To implant the device, Dr. Marzette said, a partial-thickness scleral flap is made around the limbus of the cornea (just as in a traditional trabeculectomy) through the conjunctiva and into the subconjunctival space. Through this flap, a 23-gauge needle is inserted into the anterior chamber through which the shunt is deployed into the anterior chamber. The device then drains aqueous from the anterior chamber into the subconjunctival space.

"In standard trabeculectomies, the drainage site and the lumen created are made with either a Kelly punch or forceps," Dr. Marzette said. "One of the advantages of the . . . device is that it has a fixed lumen size through which aqueous can drain. In my opinion, the . . . device can achieve a more predictable decrease in IOP compared with standard trabeculectomies. Also, different techniques used by different surgeons often can result in non-constant lumen sizes and thus different drainage amounts."

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