Corneal Patch Graft More Likely to Erode Than Scleral Graft

Ingrid Hein

March 03, 2017

In patients who have undergone implantation of a glaucoma drainage device, corneal patch grafts are much more likely to erode than scleral patch grafts, leading to more frequent revision for the prevention of infectious complications, according to a new study.

“We found the risk of graft erosion to be approximately fourfold higher in eyes with a corneal graft,” said Azra Idrizovic, DO, from the Glaucoma Center of Texas in Dallas.

What’s more, the researchers found that corneal grafts erode more quickly.

This is the first study of its size to specifically compare rates of erosion with these two types of patch grafts, said Dr Idrizovic, who presented the findings at the American Glaucoma Society 2017 Annual Meeting in Coronado, California.

“In general, we know that a large number of surgeons now prefer corneal grafts because of their widespread availability, ease of manipulation, superior cosmesis, and aesthetic appeal,” she told Medscape Medical News. “Scleral grafts tend to be thicker, bulkier, and much more visible to the patient.”

She and her colleagues decided to do the comparison after observing a high rate of corneal patch graft erosion with exposed tubes that required revision.

“The overall published rate of late postoperative graft erosion in eyes with glaucoma drainage implants is approximately 5%,” she reported. “We noticed that a significant number of these erosions were occurring in eyes with corneal grafts.”

When her team reviewed the literature to see if they could find any published articles comparing corneal and scleral patch graft erosion rates side by side, they came up empty. “There were smaller studies that compared erosion rates among different patch graft materials and identifiable risk factors for erosion, but none that specifically compared the rates of cornea and sclera in a large population of patients,” Dr Idrizovic explained.

Their retrospective study involved 329 patients (329 eyes) treated at the Bascom Palmer Eye Institute at Palm Beach Gardens in Florida — a tertiary referral center where a large number of glaucoma drainage implants are performed — from September 2011 to March 2015.

The 109 eyes that received a corneal patch graft and the 220 that received a scleral graft were followed for at least 6 months after surgery.

Of the 20 patients (6.1%) who experienced patch graft erosion and tube exposure requiring revision, 13 had corneal grafts and seven had scleral grafts. The erosion rate was significantly higher with corneal grafts than with scleral grafts (11.9% vs 3.2%).

To identify possible risk factors for erosion, the researchers assessed many clinical characteristics, such as age, sex, ethnicity, glaucoma diagnosis, previous intraocular surgeries, concomitant surgery, history of inflammation, prolonged use of topical corticosteroids, and implant location.

Significant risk factors associated with tube erosion were the use of a corneal patch graft (P = .002) and the use of topical corticosteroids (P = .01).

The reduced overall thickness of corneal grafts relative to scleral grafts might predispose to the higher erosion rates, Dr Idrizovic noted. And the prolonged use of topical corticosteroids could be related to tissue atrophy and the reduced wound healing often seen in eyes after chronic corticosteroid use.

“If a patient has a known history of inflammation and might need to be on chronic topical corticosteroids, it might be better to consider using a scleral patch graft instead of a corneal one,” she noted.

Although these findings are limited by the retrospective nature of the study and the fact that selection of patch graft material was not randomized, but instead was based on surgeon preference, they do clearly show a significantly greater rate of erosion with corneal patch grafts, Dr Idrizovic explained.

Until now, the two options have been considered interchangeable, said Steven Gedde, MD, from the Bascom Palmer Eye Institute–Anne Bates Leach Eye Hospital in Miami. “We’ve always had the feeling that both are equally effective; there’s never been any information that one is superior to the other,” he told Medscape Medical News.

Dr Idrizovic has disclosed no relevant financial relationships. Dr Gedde is a consultant for Alcon Laboratories, and has received grant support from the National Eye Institute, Abbott Medical Optics, and Research to Prevent Blindness.

American Glaucoma Society (AGS) 2017 Annual Meeting. Presented March 2, 2017.

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