FILTRATION SURGERY

An investigational soft collagen implant (XEN Gel Stent, AqueSys) designed to optimise aqueous drainage to the subconjunctival space is showing promise as a safe and effective minimally invasive alternative to traditional filtering surgery, according to preliminary data from ongoing studies presented at the XXXII Congress of the ESCRS in London.

Inga Kersten-Gomez MD, Head of the Glaucoma Department at University Eye Hospital Bochum, Germany, described the stent and reported results from up to 36 months of follow-up for 23 eyes enrolled at a single-centre study at their University Eye Hospital.

She explained that the novel device uses the most effective mechanism for achieving sustained lowering of IOP – the subconjunctival drainage pathway. However, the subconjunctival space remains non-dissected as the device is implanted via an ab-interno technique, either in a standalone procedure or combined with cataract surgery. In addition, it features some unique material and design characteristics that may enhance safety and efficacy early and over the longer term.

The implant is made of porcine gelatin crosslinked with glutaraldehyde, which is a non-resorbable material with an extensive track record for medical use. “The softness and flexibility of the implant material allow the implant to conform to the ocular tissue and for reduced forces between the implant and ocular tissue. These features should reduce risks for erosion and migration,” said Dr Kersten-Gomez.

Aqueous outflow

Measuring 6.0mm in length with a 45-micron lumen, the cylindrical implant’s dimensions are optimised to maintain a standardised rate of aqueous outflow while avoiding hypotony.

Herbert Reitsamer MD, an investigator in a multicentre European study in which the implant is placed with pre-injection of a low dose mitomycin-C, demonstrated the surgery in a video presentation.

“The collagen gelatin stent is preloaded into an IOL-like injector. The implantation procedure is rather simple, and because it is conjunctiva-sparing, it leaves open the opportunity for alternative surgical intervention in the future,” he said.

“The bleb that develops after the collagen gelatin stent procedure is deep in the intra-Tenon’s tissue. Due to the thickness of the tissue above the bleb, it is not irritating like the trabeculectomy bleb, and has a low risk of infection,” said Dr Reitsamer, Professor and Director of the Glaucoma Service at SALK/Paracelsus University of Salzburg, Austria.

Preliminary data from the single-centre study in Germany and the multicentre European trial show IOP reductions of about 30 per cent to 40 per cent at one year after surgery.

Dr Kersten-Gomez reported that the patients enrolled at the Bochum Eye Hospital had a mean preoperative IOP of 21mmHg on one or more medications. It was reduced to 15.4mmHg at 12 months, and was even lower at 24.

Inga Kersten-Gomez: inga.kersten-gomez@kk-bochum.de

Herbert Reitsamer: ha.reitsamer@gmail.com