OPEN-ANGLE GLAUCOMA

The ab-interno gelantine microdevice with subconjunctival drainage (AqueSys Inc.) offers a safe, effective and non-invasive means of lowering intraocular pressure in primary open-angle glaucoma patients, suggest the early results from the first clinical trials.

“The initial results have been very encouraging. The implant (XEN) offers a minimally invasive procedure that is potentially interesting for treating all stages of glaucoma, especially mild to moderate glaucoma and especially in combination with cataract. The mechanism of action is well understood and accepted, with an average IOP reduction of 26 per cent in our study,†Inga Kersten-Gomez MD told delegates attending the XXX Congress of the ESCRS.

Dr Kersten-Gomez, University Eye Hospital, Bochum, Germany noted that the implant is the first ab interno device which works by creating aqueous outflow from the anterior chamber into the non-dissected tissue of the subconjunctival space. The procedure uses a collagen-derived, gelatin implant that is soft and flexible when hydrated and which has been designed to mitigate traditional implant problems such as migration and erosion. Its gelatin material is biocompatible and is very well tolerated by the ocular tissues, she added.

Implanting the device is not particularly difficult and demands only a short learning curve, said Dr Kersten-Gomez. The implant is placed through a small, clear corneal incision using a preloaded inserter similar to those used for intraocular lenses. Using an ab interno approach, the surgeon places the implant with the inserter in the anterior chamber angle through the trabecular meshwork to the desired subconjunctival location.

“The procedure is straightforward and can be performed as a primary procedure or in conjunction with cataract surgery,†she said. Dr Kersten-Gomez’s prospective, openlabel, non-randomised pilot study included 23 patients with or without medications. Patients included non-refractory and refractory cases, with 10 patients receiving the implant in combination with cataract surgery.

Full ophthalmological examinations were performed including clinical assessments of IOP, anterior chamber OCT imaging, visual acuity, visual field and assessment of complications at regular follow-up intervals. Safety parameters were evaluated using IOP, visual acuity and visual field examinations.

To assess the clinical efficacy of the device, the investigators compared the mean IOP changes and the reduction in medication use from baseline to postoperatively. Dr Kersten-Gomez presented the one-year follow-up data, although she stressed that the study is ongoing and follow-up is scheduled for up to three years and that the heterogenous population is a limiting factor. In terms of results, the mean preoperative IOP of 21.0 mmHg was reduced to 16.0 mmHg at one month (-23 per cent), 15.2 mmHg at six months (-27 per cent) and 15.9 mmHg at one year (-26 per cent). The glaucoma medications were reduced from a mean of 2.2 eye drops preoperatively to 0.5 eye drops postoperatively at the 12-month follow-up point.

Dr Kersten-Gomez added that the results from Bochum University Eye-Hospital were very much in line with those reported in the ongoing worldwide multicentre clinical trial at 12 other centres, with 107 patients at the starting point and follow-ups for three years, recruitment still ongoing. Longer follow-ups are needed as well as a larger number of patients and a more homogenous population to fully assess the safety and efficacy of the implant over time, Dr Kersten-Gomez said. This method may be interesting for a broad range of surgeons performing minimal-invasive surgery, especially for mild and moderate glaucoma with or without cataract.

“One obvious advantage of the ab interno to subconjunctival approach is that it bypasses potential aqueous outflow obstructions. A single implant delivers desired effectiveness using a clinical proven outflow pathway,†she said. The fact that the approach is conjunctivasparing also means that alternative surgical options (except canaloplasty) are not compromised.