Lamellar keratoplasty: do it, but deep

Loose adherence between the stroma and Descemet’s membrane is an ideal cleavage plane for lamellar cuts.

Issue: March 1, 2000

ByMichela Cimberle

PAVIA, Italy — Deep lamellar keratoplasty (Sugita technique) is an effective, far less invasive and safer alternative to penetrating keratoplasty, according to Prof. Fernando Trimarchi, MD, of Pavia University Eye Clinic here.

“In 1 year, 50 of my patients have been treated with this technique and, comparing their results with those of penetrating keratoplasty patients, I can see a remarkable difference,” he said.

Deep lamellar keratoplasty removes only the tissue above the level of Descemet’s membrane, thus sparing the endothelium of the recipient. Since the stroma is loosely attached to Descemet’s membrane, the excision can be carried out evenly and easily, obtaining a smooth surface.

“Lamellar keratoplasty was almost entirely dismissed after the first attempts, about 50 years ago, because the technology of those days was insufficient to produce smooth, even surfaces and, consequently, good visual acuity. That’s why the majority of corneal transplants have since then been performed with penetrating keratoplasty,” Prof. Trimarchi said.

“It was thanks to the microkeratomes, which were first conceived and manufactured for refractive surgery, that lamellar keratoplasty could be resumed,” he continued. “A few years ago, however, Sugita observed that the loose adherence of the stroma to Descemet’s membrane offered the ideal cleavage plane for lamellar keratoplasty, resulting in even smoother surfaces than those obtained with microkeratomes.”

Maintaining the endothelium

The first cross incision is performed, penetrating to two-thirds of corneal thickness, dividing the cornea into four quadrants.	The four segments are removed with a diamond knife
The stroma is separated from Descemet’s membrane with a blunt spatula.	The graft is sewn in place with a double running nylon suture.

The first and most important advantage of deep lamellar keratoplasty is that it maintains the endothelium of the recipient.

With penetrating keratoplasty, the recipient’s endothelium, which may be young and healthy, is removed and often replaced with an older endothelium.

“As is well known, endothelial cells are postmitotic,” Prof. Trimarchi said. “They gradually decrease in number during the course of adult life and cannot reproduce themselves. Donor corneas are often older than the recipient’s and, therefore, have a lower number of endothelial cells. A good 80% of our cases are keratoconus patients, aged between 20 and 35 years. Maintaining their own endothelium, which still has a high number of cells, is very important. If we implant young people with older corneas, we condemn them to suffer all the problems of an impoverished, decompensated endothelium at a much earlier age.”

Maintaining the recipient’s endothelium also is an advantage from an immunological point of view, he said, as most immunological problems connected with corneal transplants originate from endothelial tissue.

“The lamellar layer on its own, devoid of the immunologically active endothelial layer, is less liable to develop antigenic reaction than a penetrating graft,” Prof. Trimarchi said. “Rejection, which is a threat in penetrating keratoplasty, does not occur when patients are left with their own endothelium.”

The mean level of postoperative astigmatism is lower with deep lamellar keratoplasty (2.5 D) than with penetrating keratoplasty, and patients “rapidly regain good vision within 2 weeks after surgery,” Prof. Trimarchi said, “whereas penetrating keratoplasty requires an average of 7 to 8 months.”

Surgical technique and results

In 1 year, Prof. Trimarchi has performed deep lamellar keratoplasty on 50 patients. They all suffered from corneal pathology that did not involve the endothelium. He described his surgical technique.

First, he performs a circular incision on the cornea with a diameter of 8 mm and trephination to two-thirds of the corneal thickness. At one-third deep, a cross-shaped cut is performed, dividing the corneal button into four quadrants, Prof. Trimarchi explained. The four segments are removed with a diamond knife.

“At this point, I perform a penetrating cut on the vertical meridian, reaching Descemet’s membrane, which can be recognized by its transparency,” he said. “The stroma is then separated from Descemet’s membrane with a blunt spatula.”

Again, two perpendicular cuts are made with Vannas scissors, delimiting four quadrants that are then removed.

A donor graft of 8.25-mm diameter is cut and, after Descemet’s membrane has been removed, it is stitched onto the eye with a double running nylon suture.

“We are systematically comparing the results of patients undergoing deep lamellar keratoplasty with the results of penetrating keratoplasty on patients of the same age, sex and pathology,” Prof. Trimarchi said. “So far we have compiled the data on 50 patients in each group, so our statistics are incomplete and limited. However, we perform an average of 170 to 180 transplants a year and, as I believe that at least 100 of them will be deep lamellar keratoplasty, we will be able to have more significant statistics by the end of this year.”

The results of deep lamellar keratoplasty and penetrating keratoplasty are presented in the accompanying table. Three parameters are compared: endothelial cell count, astigmatism and visual acuity. The mean values and standard deviation have been calculated and the data have been analyzed using the T-test.

“Comparing the data, we can see that all parameters are better in the deep lamellar keratoplasty group,” Prof. Trimarchi said. “Deep lamellar keratoplasty is certainly not an easy technique: it requires a fairly long learning curve and longer surgical times than penetrating keratoplasty. The advantages, however, make the extra effort worthwhile.”

For Your Information:

Prof. Fernando Trimarchi, MD, can be reached at Istituto Clinica Oculistica Universita di Pavia, 27100 Pavia, Italy; (39) 0382-526213; fax: (39) 0382-527006. Dr. Trimarchi has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

For deep lamellar keratoplasty, Prof. Trimarchi uses a set of instruments manufactured by E. Janach Ltd.: Trimarchi microspatula for deep lamellar keratoplasty (J2406A); and J2406.1A Trimarchi microscissors for deep lamellar keratoplasty (straight blunt blades).

E. Janach Ltd. can be reached at (39) 031-57-4088; fax: (39) 031-57-2055.