A new design of keratoprosthesis may be an option for some severe cases of ocular trauma

Of six patients who received the lens, four are counting fingers and one is 20/200. The other lost a line of acuity.

Issue: October 1, 1999

---The Keratolens showing 16 peripheral perforations.

PUERTO VALLERTA — For patients who have experienced severe, bilateral ocular trauma or who have been diagnosed with Stevens-Johnson syndrome, a keratoprosthesis may offer functional vision when conventional corneal grafts are unlikely to work.

Ana Lilia Pérez-Balbuena, MD, and Cuevas Cancino, MD, of the Asociacion Par Evitar le Ceguera en Mexico at the Hospital Dr. Luis Sanchez Bulnes in Mexico City, has implanted the device — also known as the Keratolens — in six patients with generally good outcomes. Following surgery, four patients were counting fingers from a distance of 1 m. One achieved best corrected visual acuity of 20/200, and one patient lost his preop visual acuity. Dr. Pérez-Balbuena, et al., have been implanting the lens on a limited basis for several years; however, only in 1998 did physicians begin to closely monitor the device with clinical follow-up.

Resembles button

---U-sutures for Keratolens fixation.

The keratoprosthesis, which is manufactured on a case-by-case basis by technicians of the Asociacion Par Evitar la Ceguera en Mexico at the Hospital Dr. Luis Sanchez Bulnes, is not commercially available. It is designed to closely resemble a donor corneal button in terms of its surgical handling, optics and its capacity to heal with host tissue. The PMMA device has a refractive power of 60 D and a refractive index of 1.767.

The Keratolens has an optical zone of 7 mm, surrounded by an area of 3 mm with 16 perforations that allow the device to be securely sutured into the cornea.

The keratoprosthesis is designed not to protrude though the cornea. Implantation is such that the outer surface of the device is flush with the corneal surface. Dr. Pérez-Balbuena reports that cosmetically the lens is difficult to detect. Additionally, she said the lens is well tolerated and comfortable; however, some patients have reported mild foreign-body sensation and tearing.

Implantation

The implantation technique is as follows:

First, a Flieringa ring is placed in the eye. A full thickness corneal trepanation of 7 mm in diameter is made, followed by lens extraction. Vitrectomy, Dr. Pérez-Balbuena said, is necessary in some cases.

Intralamellar stromal dissection of a 3 mm extension all around 360 grades is performed. The Keratolens is inserted and sutured in place.

Sutures are placed through the posterior wall of the recipient’s cornea, through perforations in the Keratolens and in the interior wall of the cornea, where it is tied. Typically, Dr. Pérez-Balbuena said she uses eight sutures of 9-0 Vicryl in a U fashion.

“It is difficult at this point to evaluate the safety and efficacy of the Keratolens because the number of cases and the time of follow-up are not sufficient,” Dr. Pérez-Balbuena said. “To fully evaluate this procedure, we will require a larger number of cases, as well as longer follow-up.”

Dr. Pérez-Balbuena presented a paper on the Keratolens at the 5^th International Course on Cornea and Refractive Surgery held here.

Case 1: preop severe chemical burns.	Case 1: 1 month postop.
Case 2: preop cornea following pemphigoid.	Case 2: 6 weeks postop.

For Your Information:

Ana Lilia Pérez-Balbuena, MD, can be reached at the Asociacion Para Evitar le Ceguera en Mexico, Hospital Dr. Luis Sanchez Bulnes, Vincente Garcia Torres No. 46, Col. San Lucas, Coyoacan 04030, Mexico; (52) 5-659-3597; fax: (52) 5-659-3308; e-mail: apecmex@yahoo.com. Dr. Pérez-Balbuena has no direct financial interest in any of the products mentioned in this article, nor is she a paid consultant for any companies mentioned.