Drainage device for scleral flap

Placement of the EX-PRESS™ glaucoma drainage implant (Alcon) beneath a scleral flap can provide an IOP reduction equivalent to that of trabeculectomy, possibly with a lower rate of complications, said Carlo Traverso MD, University of Genoa, Genoa, Italy. “Results coming from numerous centres show that the implantation of the EX-PRESS device under a scleral flap is clinically safe and effective in maintaining a durable and large reduction in IOP,†Prof Traverso told the attendees of the EGS-sponsored Glaucoma Day at the XXIX Congress of the ESCRS.

The EX-PRESS implant is a stainless steel device consisting of a 27-gauge shaft with an outer diameter of 0.4mm with either a 50 micron or 200 micron axial lumen and a bevelled tip to allow easy insertion. The shaft terminates in a faceplate that fits under the scleral flap.

“During trabeculectomy there is one part which is a little bit cumbersome in my hands, and that is the ‘ectomies,’ that is, the sclerectomy or corneosclerectomy and the iridectomy. The idea of this implant was that it would allow to perform filtration surgery with still a lot of flow but without the ‘ectomies’,†he said.

Prof Traverso noted that the implant was originally designed to drain from the anterior chamber directly to the subconjunctival space with just a conjunctival flap modulating the flow of aqueous.

The technique initially appeared to be very successful. In a study involving patients undergoing combined phacoemulsification and filtration procedures, the mean IOP remained below 20 mmHg for four years (Traverso et al. Br J Ophthalmol 2005). However, it became clear that when implanted in this way the filtration device would rotate slightly in some cases, resulting in extrusions, Prof Traverso noted.

Elie Dahan MD, from South Africa therefore proposed implanting the device under a scleral flap. The technique is more complicated than the original procedure but is less traumatic to the eye than trabeculectomy in that it does not require an iridectomy or removal of scleral tissue, Prof Traverso said.

In a study involving 37 eyes of 35 primary open angle glaucoma patients, implantation of the device under a scleral flap reduced mean IOP from a preoperative value of 27.2 mmHg to 12.4 mmHg at one year’s follow-up. Nearly 80 per cent of eyes had an IOP below 18.0 mmHg, he noted. Moreover, IOP remained stable throughout follow-up, which reached two years in some patients (De Feo et al, Can J Ophthalmol, 2009; 44:457-462).

Several other studies have yielded similar results, including a prospective randomised study in which primary open-angle patients underwent implantation of the EX-PRESS shunt or trabeculectomy. The study showed that there was no significant difference between the success rates of the two groups (P = 0.594). However, early postoperative hypotony and choroidal effusion were significantly more frequent in the trabeculectomy group (P < 0.001) (Maris PJG, et al. J Glaucoma. 2007; 16:14-19).

“There are still some unresolved issues, for example, we need to see some long-term comparison studies with other devices, and a cost benefit analysis; moreover we need to determine whether it’s better to use the model with the 50 micron diameter lumen or the 200 diameter lumen,†Prof Traverso said.