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Superficial keratoplasty an option for anterior corneal disorders
At 1 month follow-up, all eyes had corrected vision of 20/40 or better, and less than 4 D of astigmatism.
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NUREMBERG — A form of lamellar keratoplasty that involves the transplantation of only a superficial layer of corneal tissue appears to be an effective treatment for patients with certain corneal disorders, a small study indicates. The technique also offers patients faster visual recovery compared to other forms of keratoplasty, according to the lead investigator.
Massimo Busin, MD, presented the results of a prospective study evaluating microkeratome-assisted superficial anterior lamellar keratoplasty (SALK) here at the German Ophthalmic Surgeons meeting.
The study included patients with subepithelial corneal scarring, including cases following refractive surgery, patients with subepithelial irregularities, such as Bowman’s membrane dystrophy, and patients with superficial stromal opacities, such as granular dystrophy.
Preoperative image of an eye with granular dystrophy before undergoing microkeratome-assisted superficial anterior lamellar keratoplasty (SALK). Same eye with granular dystrophy 1 day postop after undergoing microkeratome-assisted SALK. Images: Busin M |
Surgical procedure
Because it is essentially an extraocular procedure, SALK can be performed using topical anesthesia. It has the advantage of preventing scar formation, while also allowing for subsequent correction of residual refractive errors using LASIK, Dr. Busin said.
A microkeratome was used to create a donor corneal cap in much the same way a LASIK flap is created. A section of lamella was then removed from the recipient cornea and replaced with one of similar size — 130 µm to 160 µm thick and 9 mm to 9.5 mm in diameter, Dr. Busin said.
Using 10-0 nylon sutures, a donor cornea is mounted on an artificial anterior chamber, and a microkeratome fitted with a 130-µm head is used to create a free cap on both the donor and the recipient cornea, Dr. Busin said.
The anterior surface of the donor graft should be marked prior to cap removal to ensure proper placement onto the recipient, he noted.
The average diameter of the corneal graft is around 9 mm, although the diameter is not as important as graft thickness. A graft of 7.5 mm to 8 mm would be adequate for the procedure, he said.
“The thickness is critical, as thicker grafts would not adhere to the recipient cornea without using traditional radial sutures. This thin graft, which is basically a free cap, requires just overlying sutures or even only a contact lens to keep it in place,” Dr. Busin said.
When overlying sutures are needed, the sutures are applied by passing the needle three times through only the recipient’s superficial cornea, close to the limbus, Dr. Busin said.
“The result is a sort of Star of David pattern. The sides of the star cross over the graft, keeping it in position,” he said, noting the sutures are normally removed 2 to 3 days after surgery, but never later than 1 week postop.
Postoperatively, Dr. Busin usually prescribes a combination of topical dexamethasone and tobramicin drops, which are applied every 2 hours for 10 days. The drops are then tapered over the following 6 to 8 weeks.
Prospective study
Dr. Busin and colleagues in Forli, Italy, have been performing the microkeratome-assisted SALK procedure since July 2001 as part of a prospective study involving 20 eyes — 12 eyes with corneal dystrophy, six eyes with opacities following refractive surgery and two eyes with scars caused by keratitis.
Preoperatively, best corrected visual acuity was 20/40 and 20/50 in one eye each, 20/60 in four eyes, 20/80 in eight eyes, and ranged from 20/100 to 20/400 in the remaining six eyes, according to the study.
At 1 month follow-up, BCVA improved to 20/40 in six eyes, 20/30 in seven eyes, 20/25 in five eyes and 20/20 in two eyes. At 6 months follow-up, BCVA remained 20/40 in four eyes, 20/30 in six eyes, 20/25 in six eyes, and 20/20 in two eyes.
Among 13 eyes available for follow-up at 1 year, three eyes achieved BCVA of 20/40, five achieved BCVA of 20/30, four achieved BCVA of 20/25, and one achieved BCVA of 20/20, according to the study.
In all eyes, postoperative astigmatism remained 4 D or less, Dr. Busin said, noting the most common postoperative complication was epithelial ingrowth at the interface.
“If the epithelium in the interface is isolated from the surface, it can be simply watched and most of the time it will disappear. However, if there is a channel making the surface communicate with the interface, new epithelial cells will continue to ingrow and surgical debridement is mandatory,” he said.
For Your Information:
- Massimo Busin, MD, can be reached at Via Sisa 33, 47100 Forli, Italy; 39-05-4345-4180; fax: 39-05-4345-4300; e-mail: mbusin@alinet.it.
- Michael Piechocki is an OSN Staff Writer who covers all aspects of ophthalmology, specializing in oculoplastics. He focuses geographically on Europe and the Asia-Pacific region.