Gelatine stent a useful surgical alternative in refractory glaucoma
The glaucoma surgery device gelatine stent helps reduce intraocular pressure (IOP) and medication use while having a favourable safety profile in patients with refractory glaucoma, providing an attractive minimally invasive surgical alternative to this population, according to the results of an open-label, multicentre study.
In 65 patients (53.8 percent female) who failed prior filtering/cilioablative procedure or had uncontrolled IOP on maximum-tolerated medical therapy, the stent was placed ab interno following pretreatment with mitomycin. Mean age of the cohort was 70 years, with medicated IOP of ≥20 and ≤35 mm Hg and visual field mean deviation of ≤−3 dB.
At 12 months, the stent met the primary endpoints of patients achieving ≥20 percent IOP reduction from baseline on the same or fewer medications (76.3 percent) and mean IOP change from baseline (−6.4 mm Hg; 95 percent CI, −8.7 to −4.2). [Am J Ophthal 2017;doi:10.1016/j.ajo.2017.07.023]
Results were similar in an analysis excluding four patients with missing data and nine who required glaucoma-related secondary surgical intervention, with 75.4 percent reporting ≥20 percent IOP reduction from baseline on the same or fewer medications and −9.1 mm Hg (−10.7 to −7.5) mean IOP change from baseline. The mean number of IOP-lowering medications used decreased from 3.5 at baseline to 1.7 at 12 months.
In terms of safety, no intraoperative complications or unexpected postoperative adverse events (AEs) were reported. Most AEs were mild to moderate in severity, with commonly reported AEs including needling (without sight-threatening complications), nonpersistent loss of best-corrected visual acuity and transient hypotony (requiring no surgical intervention).
Researchers pointed out that the ab interno placement of the gelatine stent appears to a useful minimally invasive surgical alternative to patients with refractory glaucoma, given the present data and recent reports stating that the device can be successfully implanted in a wide range of glaucoma stages (mild to advanced), providing similar IOP lowering with and without cataract surgery, and that the risk of failure is not markedly different between patients given the gelatine stent and those who received trabeculectomy. [AGS 2016:161–162; Ophthalmology 2017;doi:10.1016/j.ophtha.2017.05.004]
“The main reason for the observed needling rate in [the present] study was likely related to opening the conjunctiva, which was required for the application of mitomycin C during implantation and may have induced scar formation,” they added.
Approved by the US Food and Drug Administration in November 2016 for the management of refractory glaucoma, a stent made out of a soft gelatine material derived from porcine dermis swells when hydrated. In doing so, the device is secured in its intended position as it adapts to the shape of surrounding tissues to create a permanent channel from the anterior chamber to the subconjunctival space.
The stent also allows ab interno placement, which lowers the risk of bleb infection or leak, as well as avoids the natural drainage pathways that often become obstructed and cause elevated IOP. Furthermore, the device does not raise unexpected safety concerns, unlike other glaucoma aqueous shunts which have been associated with cases of suprachoroidal haemorrhage, diplopia, severe corneal issues, retinal detachment, flat anterior chamber, loss of light perception and blebitis, among others. [Ophthalmology 2016;123:2103–2112; BMC Ophthalmol 2016;16:83; PLoS One 2015;10:e0118142]
The study has several limitations, including the absence of comparator and the open-label design, and the failure to consider the potential effects on the study eye of changes in the fellow eye.
“In addition, the study population included ≤5 percent of Asian patients, and ≤13 percent of patients with pseudoexfoliation, pigmentary or mixed-mechanism glaucoma. Nonetheless, our findings are generalizable to men and women with refractory glaucoma characterized by uncontrolled IOP on maximum tolerated medical therapy and open angles,” researchers said.