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Visual recovery takes place as early as one month after surgery with endokeratoplasty
Only the posterior part of the cornea is replaced, hosted under the patient’s own anterior corneal lamella.
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RAVENNA, Italy – A new technique of transplantation of the corneal endothelium preserves the recipient anterior cornea, significantly reducing the time to achieve useful vision. The procedure, named endokeratoplasty (EKP), was presented by its co-author, Massimo Busin, MD, at the meeting of the Italian Society for Corneal Transplantation here. Prof. Busin’s co-author is Robert C. Arffa, MD, of the University of Pittsburgh Medical Center.
“EKP is based on the fact that, although the functional integrity of the endothelium is necessary to maintain corneal transparency, the refractive characteristics of the cornea are determined by its anterior surface. Traditional penetrating keratoplasty (PKP), replacing the central corneal in its entire thickness, restores endothelial functions but at the same time strongly affects the refractive features of the corneal surface,” Prof. Busin said.
In PKP, he noted, corneal distortion results from many factors, such as host-graft disparity, suturing technique and the slow healing of the vertical corneal wound. In the majority of cases, useful stable vision is achieved many months after surgery and often not before suture removal.
To prevent these problems, EKP replaces only the posterior part of the cornea, including the endothelium and the posterior stroma. The graft is hosted under the patient’s own anterior corneal lamella, including the Bowman’s layer, which is then sutured back into its original position.
Procedure
The procedure uses the LASIK technique to perform a corneal flap. After the patient has been given local anesthesia, the inferior limbal cornea is marked and the loose corneal epithelium is gently scraped off. A centered, hinged flap of 9.5 mm, 160 µm thick, is performed with a microkeratome. Prof. Busin uses the Carriazo-Barraquer microkeratome (Moria) and the down-up technique. The flap is open and a 6.5-mm button is removed from the underlying cornea, using a trephine and corneal scissors.
The donor cornea is fitted in an artificial anterior chamber device (Moria) and an SLK I microkeratome is used to remove a superficial lamella of 160 mm. Then the cornea is placed on a Kaufman teflon block with the endothelium facing up and a 7-mm button is punched out by means of a hand-held trephine.
“At the beginning of my experience with EKP, I used to transplant the entire thickness of the donor button without cutting a superficial flap. I thought the presence of the Bowman’s layer could prevent scarring and opacification. We only removed the epithelium. However, two cases of interface epithelial ingrowth persuaded me to remove the donor anterior stroma,” Prof. Busin said.
The donor button is then placed into the recipient bed. “Initially we thought that success of surgery depended on tight suturing of the deeply located donor button to the recipient bed,” Prof. Busin said. “On the contrary, we found that this caused peripheral tissue rolling and consequent central flattening of the donor button. As a result, the donor button was kept away from the overlying flap and the cornea did not clear unless we removed the deep sutures within few days.”
“For this reason we started to place just an interrupted 10-0 nylon suture at the 12 o’clock position and lately we have completely abolished the deep sutures. Somewhat to our surprise, despite the absence of any suture anchoring the donor button to the recipient bed, it is perfectly adherent to the overlying corneal flap. At the end of surgery, the corneal flap is flipped over, back into position, and fixed with a running 10-0 nylon suture,” he said.
“With this procedure, it is not necessary to apply a high suture tension to close the wound and make it watertight,” Prof. Busin said. “That’s why corneal distortion is minimized and there is only a little difference in refraction before and after suture removal.”
Fast, promising results
At the meeting, Prof. Busin performed EKP on an 83-year-old male patient affected by bullous keratopathy secondary to cataract surgery and IOL implantation. His previous experience encompasses more than 20 patients.
“Complications were very few,” he said. “The already mentioned case of flap melting was easily recovered by removing the diseased flap and resuturing the donor button. We had a case of traumatic dehiscence and three cases of astigmatism greater than 4.5 D before suture removal. In all the other cases, results were very rewarding and surprisingly rapid. Complete re-epithelialization and clearing of the cornea occurred within 2 weeks, and the internal sutures, when present, were removed early after surgery or spontaneously dissolved within 2 months. The external nylon suture was removed 3 to 4 months postoperatively.”
“After 1 month only, patients had useful uncorrected visual acuity of at least 20/400 and best corrected visual acuity between 20/100 and 20/40. Suture removal did not affect these values substantially. Astigmatism had a regular morphology and was within 4 D. Sphere was between –1 D and –4 D.”
Prof. Busin suggested that the corneal flap might also act as a soft contact lens, smoothing the underlying irregularities.
“This is another one of the many advantages of the technique. I am also fairly convinced that the deep location of the donor button might reduce the risk of immune reaction, but this will have to be proved by further studies,” he said.
For Your Information:
- Massimo Busin, MD, can be reached at +(39) 0543-799033; fax: +(39) 0543-68826; e-mail: mbusin@alinet.it or mbusin@yahoo.com.