According to researchers from United States and Ireland, thinning of gamma-irradiated sterile cornea (GISC) patch grafts exposes the tube followed by the aqueous drainage devices (ADDs) surgery.

In an article published in JAMA Ophthalmology, Dr. Jampel from Johns Hopkins Hospital, Baltimore and colleagues noted that GISC patches are the most popular choice, because it reduces the risk of disease transmission. Also, it offers improved cosmesis due to its transparency. Further they added, the extrusion of tube through the conjunctiva is a serious complication of ADD implantation surgery.

Dr. Henry D. Jampel mentioned in his email that their findings that demonstrate thinning of corneal patch grafts followed by ADD surgery provides an insight into the grafts that does not represent a conclusive solution for the tube extrusion.

The research team conducted a transversal study of graft thickness using anterior-segment optic coherence tomography to evaluate the potential for subsequent tube exposure. The team focused on patients who underwent the surgery with GISC patch grafts in the time period of 2010 to 2016. A total of 107 patients (120 eyes and 120 ADDs) with GISC patch grafts were evaluated for the graft thickness vs. time after ADD surgery.

They found 410 micrometers median graft thickness within two weeks of post-surgery and 1.7 years as mean measurement time after surgery. Also observed, a gradual thinning of GISC patches grafts after surgery. During the study period, 16.6% of eyes (20 ADDs) were found with no GISC patch graft.

Dr. Andrew Rabinowitz of Phoenix, Arizona commented that, different materials were used in the devices to reduce the rate of tube erosion through the sub-conjunctival space to the extra ocular environment. Exposure of the tube could be a disastrous consequence of ADD surgery.

"Although surgeons are always looking for better ways to improve surgical outcomes, it does not appear as though the use of GISC offers any major advantages to the historically used tissues. The durability of GISC appears to decrease steadily with time," Dr. Rabinowitz said. The GISC has high erosion potential, which leads to the exposure of tube through the conjunctiva. "The integrity and protective benefit of GISC wane dramatically in just a few short years following the ADD surgery. The study leads the reader to realize that materials other than GISC should be considered when placing an ADD for glaucoma management."