Hard Graft
Might crosslinking patch grafts placed during glaucoma drainage device implantation eliminate conjunctival erosions?
Glaucoma drainage devices (GDDs) can be a great option for intraocular pressure reduction in some patients with glaucoma or ocular hypertension, with reductions equivalent to those achieved with trabeculectomy in some cases, and with fewer complications (1), although “fewer” does not equal “none.” Conjunctival erosions can occur in 5–10 percent of patients, exposing the tube or shunt, and putting the patient at risk of number of complications, including endophthalmitis (2), (3). One way to lower this risk is to cover the GDD with a “patch graft” during surgery, and short-duration studies have certainly reported good outcomes from using donor cornea tissue (4), (5).
However, this is a precise art: if the graft is too thick, it may lead to bleb formation (or other complications), and if too thin, it may fail (6). Ideally, patch grafts need to be strong enough to provide sufficient and durable support to the cornea to prevent device exposure, yet thin enough to avoid inducing complications. Cue corneal crosslinking…
Recognizing the value that the approach could offer in this scenario, one research group have taken anterior lenticules from Descemet’s stripping automated endothelial keratoplasty (DSAEK) corneas (300–350 µm), and “augmented” the tissue via UV-riboflavin crosslinking. They then implanted the crosslinked grafts over the drainage device in 10 patients undergoing GDD surgery. Interim 6-month results (7) were presented at the recent EVER congress in Nice, France and demonstrated no intra- or post-operative complications, with no grafts becoming eroded or GDDs becoming exposed.
The study is anticipated to last 36 months, but from these interim results, the researchers note “UV-riboflavin crosslinking of corneal tissue appears to be a safe modification of GDD surgery.” Understandably, the team note that “prospective randomized trials are needed to compare augmented tissue with standard corneal grafts, and to define the optimal surgical strategy” – but it’s certainly one strategy to file under “why didn’t we think of that one before?”
- SJ Gedde et al., “Treatment outcome in the tube versus trabeculectomy (TVT) study after five years of follow-up”, Am J Ophthalmol, 153, 789–803 (2012). PMID: 22245458.
- V Trubnik et al., “Evaluation of risk factors for glaucoma drainage device-related erosions: a retrospective case-control study”, J Glaucoma, 24, 498–502 (2015). PMID: 24326968.
- SJ Gedde et al., “Late endophthalmitis associated with glaucoma drainage implants”, Ophthalmology, 108, 1323–1327 (2001). PMID: 11425695.
- YJ Daoud et al., “The intraoperative impression and postoperative outcomes of gamma-irradiated corneas in corneal and glaucoma patch surgery”, Cornea, 30, 1387–1391 (2011). PMID: 21993467.
- O Spierer et al., “Partial thickness corneal tissue as a patch graft material for prevention of glaucoma drainage device exposure”, BMC Ophthalmol, 16 (2016). PMID: 26920383.
- EyeWiki, “Glaucoma drainage devices”, (2016). Available at: eyewiki.aao.org/Glaucoma_Drainage_Devices. Accessed October 20, 2016.
- D Stone et al., “Augmentation of corneal graft tissue with UV-riboflavin crosslinking: a pilot study”. Poster presented at the European Association for Vision and Eye Research; October 6, 2016; Nice, France. Poster #T026.
