LaserVision.gr | Managing Severe External Disease and Corneal Trauma

TREATING OCULAR CHEMICAL INJURY and severe external disease is very different outside the United States. The scarcity and relatively poor quality of donor corneas combined with unique environmental conditions challenge ophthalmologists in managing these patients.

One common problem throughout Europe, especially southern Europe, involves the widespread use of lye at construction sites. The material, which is deposited on streets during construction, is hazardous for children and causes a relatively high rate of ocular chemical burns.

We have treated several patients who have suffered monocular chemical burns with autologous conjunctival grafts from the healthy eye onto the chemically injured eye. This is followed by adjunctive grafting of amniotic membrane to serve as a biologic bandage contact lens.


Left: A 68-year-old male with a long history of pemphigoid. This eye had hand-motion vision. Right: The same eye six months following type 1 Dohiman keratoprosthesis. Visual acuity is 20/50.

We istill topical anesthesia in the donor eye and use peribulbar anesthesia for the host eye. I incise a 25-30 degree arc strip of Jimbal tissue 2 to 3 mm adjacent to the conjunctiva from the superior and inferior aspects of the donor eye under topical anesthesia.

A side view of a PMMA Dohiman
keratoprosthesis type I

We perform extensive cicatricial tissue debridement in the injured eye and, if necessary, symblepharon lysis. The corresponding host sites for theconjunctival limbal autografts are prepared. We use wet-field cautery for hemostasis, which can be quite challenging in these eyes, depending on the degree of chemical scarring.

I suture the conjunctival autografts, oriented to correspond exactly to their harvested sites from the donor eye, in place with 10-0 nylon. The ocular surface is then covered with an amniotic membrane graft, which acts as a biological bandage contact lens for the newly transplanted limbal stem cells. The graft also helps to avoid symblepharon reformation. A topical fluoroquinolone is used for four weeks postop.

The results of this procedure, first described in 1977 1 and further popularized in the late 1980s, 2 appear very promising. Within several months new limbal stem cells repopulate the conjunctival surface, which undergoes a significant reduction in scarring and haze caused by severe external disease. Although the treated eye rarely regains the corneal clarity and health of the donor eye, improvements in comfort, aesthetics, and visual rehabilitation are quite dramatic.

If the corneal, scarring is deep and significant, a conjunctival autograft performed before a penetrating graft achieves a much better outcome in these chemically injured eyes. I perform the conjunctival autograft at least three months before the corneal transplantation to prepare the host bed, and to treat the external disease resulting from the chemical burn. 3

Due to the scarcity of good-quality corneal donor tissue, we sometimes resort to deep lamellar keratoplasty, a time-consuming and technically challenging technique rarely used in the United States. Easy access to well-preserved donor corneas makes a penetrating corneal keratoplasty a highly successful and much less time-consuming procedure in the United States than in areas of the world where corneal tissue is less available. When it is available, donor tissue is usually of poorer quality due to excessive preservation-to-transplantation time, as well as the individual indices of the donor tissue.

For these reasons, ophthalmologists have turned to deep lamellar keratoplasty to treat corneal opacities not due to corneal endothelial dysfunction. The procedure's advantages include a very low incidence of rejection and, because no corneal endothelial cells are transplanted, the preservation-to-transplantation time and donor endothelial cell count are less critical. But deep lamellar keratoplasty is not without problems:

The technique is lengthy and requires significant surgical skill. Additionally, debris can be trapped in the host/donor interface during the. procedure and the interface itself can become epithelialized, impeding visual rehabilitation.

A new technique introduced outside the United States involves the use of microkeratomes to facilitate deep lamellar keratoplasty. One variation of the technique includes a 400-pm microkeratome pass of the host cornea, followed by a similar procedure on the whole donor eye. The donor comeal lenticule is sutured on the host cornea, either with interrupted or interrupted and running sutures.

Although allograft limbal-scleral transplantation has shown promise in managing severe, visually debilitating external disease, keratoprosthesis remains an effective tool to restore vision in these eyes. Such severe and advanced disease is rare in the United States, but it accounts for a significant portion of visual debilitation in other parts of the world.

This patient underwent limbal stem cell autotransplatation, and five months later, a penetrating keratoplasty. Visual activity is now 20/40

Keratoprosthesis is the treatment of last resort for short- or long-term visual rehabilitation in cases of severe external disease, including advanced ocular cicatricial pemphigoid, chemical burns, Stevens-Johnson syndrome and idiopathic corneal opacifications. Therefore, the practical indication for a keratoprosthesis is to provide a transparent "window" to replace an irreversibly scarred and opadfied cornea.

There are several keratoprosthetic devices in use, including the Dohiman, Worst, Stampelli, and Cardona keratoprostheses. Most of these devices have a PMMA central optic, usually embedded owithin a vehicle "material." The vehicle material in the Dohiman keratoprosthesis is partially PMMA and donor corneal tissue. The diameter of the PMMA insert is 3 mm and provides a postoperative visual field of 25 to 30 degrees.

I have had good success with the Dohiman keratoprosthesis. Grafting the device is a lengthy procedure that usually involves a reconstruction of the anterior segment of the eye.

First, all cicatricial tissue is removed. Then I implant an Ahmed valve to control the glaucoma that usually accompanies keratoprosthesis surgery. Next, I perform a penetrating trepbrnation of the central comeal host and a total iridectomy, lensectomy and/or IOL removal. Depending on the host's phakic status, I perform a generous anterior vitrectomy.

At this point, the Dohiman keratoprosthesis, previously placed onto a large host-donor graft, is transplanted. I suture the keratoprosthesis/donor cornea complex in place, similar to a penetrating keratoplasty, with interrupted sutures. A total conjunctival flap is used as a final step to minimize problems with keratoprosthesis/host interface melts. I prefer to use an amniotic membrane graft as a biologic bandage lens.

Depending on the state of the posterior segment, a keratoprosthesis can significantly restore visual acuity. Several of my patients 4 have achieved visual acuities ranging from 20/20 to 20/40. Some of the disadvantages of the device include a tedious and meticulous followup; the treatment and prevention of glaucomatous damage; the avoidance of secondary infection due to the prosthesis itself; and maintaining the integrity and adhesion of the tissue around the keratoprosthesis.

Thoft RA. Conjunctival transplantation. Arch Ophthalmol 1977;95:1425-9.
Kenyon KR, Tseng SCG. Limbal autograft transplantation for ocular surface disorder. Ophthalmology 1989;96:709-14.
Kanellopoulos AJ, Pamel GL, Nejat M. Clinical evaluation of human amniotic membrane transplantation in the surgical management of severe ocular surface disease. Presented at the 103rd annual meeting of the American Academy of Ophthalmology; October 25. 1999; Orlando, Fla.
Netland PA, Terada H, Kanellopoulos AJ, Dohiman CH. Glaucoma associated with keratoprosthesis. Poster presented atthe 100th annual meeting of the American Academy of Ophthalmology; October 27-31, 1996; Chicago, III.