Strategies for surgical intervention aid in peripheral corneal disease

Take-Home

Peripheral melting disorders require surgical intervention when all else has failed and there is an impending risk of perforation. A peripheral C- or banana-shaped graft can restore tectonic integrity while maintaining a reasonable corneal contour to preserve vision.

By Lynda Charters; Reviewed by Donald Tan, FRCSE, FRCSG, FRCOphth

Singapore-Surgical management of peripheral melting disorders may be required when all else has failed and an impending risk of perforation may exist.

Primary problems associated with peripheral corneal diseases are disease progression in the form of progressive corneal thinning and corneal perforation, as well as secondary infection, irregular astigmatism, and ectasia.

C- or banana-shaped grafts applied in the peripheral cornea can help maintain the corneal integrity and contour.

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“The principle of surgical management of these complications is halting disease progression medically or systemically (by treating inflammatory or infection causes), and surgically restoring corneal integrity and anatomy by tectonic reconstruction of the peripheral cornea,” said Donald Tan, FRCSE, FRCSG, FRCOphth.

Adjunctive procedures are gluing procedures, transplantation of amniotic membrane, and conjunctival resection.

A minimalist approach is suggested in these cases, said Dr. Tan, the Arthur Lim Professor of Ophthalmology Endowed Chair, Duke-National University of Singapore Graduate Medical School, and professor of ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore.

An anterior lamellar patch graft may be the best choice if the endothelium is not affected.

“This will avoid involving the unaffected central cornea,” Dr. Tan said.

“The goal in these cases is to preserve or restore visual function,” he said. “To do so, topographic changes and irregular astigmatism must also be addressed over the long term.”

Though not much information is in the literature concerning tectonic keratoplasty, it has been Dr. Tan’s experience that tectonic grafts do well. However, complications can include active keratitis, postoperative melt, and inflammation.

“The graft survival rate is about 50% [at] 5 years postoperatively after penetrating keratoplasty,” he said. “Lamellar keratoplasty has slightly better outcomes.”

Various approaches to tectonic keratoplasty include using small-patch grafts, mushroom grafts, or onlay of anterior lamellar grafts to correct peripheral corneal disorders. A tuck-in lamellar keratoplasty can be performed to treat peripheral ectasias.

Match-and-patch grafts

Dr. Tan described his approach as “match-and-patch peripheral grafts” that are C-shaped to avoid the central cornea.

“The idea is to have banana-shaped grafts that are essentially anterior lamellar patch grafts shaped to restore integrity of the peripheral melting area,” he said. “The advantages are prevention of endothelial rejection and minimization of intraocular surgery and complications, as well as maintenance of the spherical corneal shape.”

In addition, the procedure can be performed in the presence of a small- or moderate-sized perforation, he explained. This provides tectonic reconstruction of the peripheral corneal anatomy without replacing the central cornea.

“The crescentric-shaped graft also respects the central corneal shape,” he said. “The sutures can be tightened and with subsequent suture removal the astigmatism can be reduced. In addition, the procedure may be repeatable.”

Dr. Tan reported the outcomes in 34 cases of Mooren’s ulceration in 22 patients treated with “banana” grafts who were followed for about 5 years.

“About 50% of these patients required a second graft because of disease recurrence,” he said. “Tectonic success was about 88%.”

Surgical procedure

The procedure to create the recipient bed is not highly difficult, but requires careful attention to detail to reconstruct corneal anatomy, Dr. Tan noted. He described the technique in a patient with a banana-shaped corneal melt. Marking trephines are used to regularize the slightly irregular area of corneal melting. A central trephine is used to mark the central radius. A 13- or 14-mm trephine is used to mark the peripheral radius.

Smaller-diameter dermatological trephines are useful to mark the edges of the banana shape, he noted.

Dr. Tan cautioned against causing a perforation. Free-hand lamellar dissection is performed using a crescent blade.

The donor procedure is performed using a 14-mm orbital glass implant that is covered with cloth. The implant is placed in a punch and sutured, which facilitates any desired tissue shape, he explained.

The corneal tissue is matched to the bed and sutured in place. A lamellar or full-thickness dissection can be performed using the same marking trephines used for the recipient bed.

Some considerations

One factor to consider is whether a patient has ectasia. Cases of classic Mooren’s syndrome, Dr. Tan pointed out, may not have ectasia. However, other peripheral noninflammatory disorders, such as pellucid marginal degeneration, have substantial thinning, protrusion, and bulging.

“In the thin periphery, the same C-shaped lamellar graft can be applied,” he said. “However, ectasia can be prevented by using a smaller-sized donor tissue that is sutured tightly with interrupted 9/0 nylon sutures, which splints the cornea, and negates the ectasia.”

In this situation, the compressive lamellar donor graft is narrower than the recipient bed.

“We can effectively reduce a great deal of astigmatism and ectasia using this type of graft and tight suturing,” he said. “The intended overcorrection can subsequently be reversed with careful sequential suture removal several months later.”

Dr. Tan highlighted the case of a 76-year-old woman with rheumatoid arthritis. In 2006, the left eye of the patient had a corneal melt adjacent to a pterygium, which was excised and a conjunctival graft put into place. In 2008, the corneal again melted and the rheumatoid arthritis was confirmed. The patient was treated for years with a systemic medication. A second lamellar patch procedure was performed, demonstrating the repeatability of the surgery.

Three years later, another melt occurred away from the graft with tapering of the systemic medications. In 2011, another melt occurred and a fourth graft was applied. In 2014, an intrastromal crystalline opacity developed between the four grafts, which was suspected to be a fungal infection and progressed to another melt.

Ultimately, a central deep anterior lamellar keratoplasty was performed that encompassed all the previous grafts. In this ongoing case, the patient currently has 20/200 vision.

Donald Tan, FRCSE, FRCSG, FRCOphth

E: donald.tan.t.h@snec.com.sg

Dr. Tan has no financial interest in the subject matter