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Lamellar keratoplasty may be an option for patients with keratoconus
ALK for keratoconus treatment allows the surgeon to rebuild normal curvature, replace the stromal scar and preserve endothelium.
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FORLI, Italy — Automated lamellar keratoplasty is a simple and efficient treatment for keratoconus, and patients enjoy fast visual rehabilitation.
Massimo Busin, MD, a professor of ophthalmology in private practice here, reported on a series of keratoconus patients on whom he performed automated lamellar keratoplasty (ALK). He discussed results, indications for the procedure, its advantages and disadvantages at a course sponsored by Moria, prior to the Video Refractiva 2002 meeting in Milan.
“To date I have used this technique in over 20 patients and in my hands it is the technique of choice for moderately advanced to advanced keratoconus,” he told Ocular Surgery News.
“Patients with keratoconus may have distorted curvature and modified transparency of their cornea. The typical therapy for keratoconus in patients with normal corneal transparency includes glasses, contact lenses or conservative surgery,” he said.
Dr. Busin described this conservative surgery as possibly epikeratophakia, intrastromal segment or perhaps an excimer laser procedure.
For keratoconus patients who have scarred corneas, the appropriate therapy would be “destructive surgery,” consisting of penetrating keratoplasty (PKP) or lamellar keratoplasty, he said. A standard PKP intraocular procedure for keratoconus include transplantation of a full-thickness donor button, 8 mm in diameter. A major problem with this, he said, is that it results in relatively frequent immunological rejection.
“Previous studies have shown that about 20% of keratoconus patients undergoing PKP experience an episode of immunological rejection within 7 years after surgery. Still, at the present time PKP is the most used technique for the surgical treatment of keratoconus,” he said.
Rebuild curvature
Using lamellar keratoplasty for keratoconus, the surgeon can rebuild normal curvature, replace the stromal scar and preserve endothelium.
“The procedure is performed at partial thickness, about 9 mm to 9.5 mm diameter, using an extraocular intervention,” Dr. Busin said.
He added that ideally, the technique for performing lamellar keratoplasty should be simple and therefore easily reproducible, safe and come with a reasonable price tag. The currently available dissection techniques for performing lamellar keratoplasty are manual, automated and laser-assisted.
“Manual dissection is technically difficult, with poor optical quality at the interface. Patients often end up with poor visual acuity,” he said.
Another drawback is that in performing a deep anterior lamellar keratoplasty manually, all stroma is eliminated and the endothelium exclusively is preserved. This is technically difficult to do, he said.
A laser-assisted dissection is also difficult, technically and logistically; safety, sterility and cost are all major factors as well with this technique.
Automated dissection
Automated dissection is technically easy, and the surgeon preserves optical quality of the interface.
“Microkeratome-assisted lamellar keratoplasty allows patients to achieve 20/20 vision as seen with LASIK,” Dr. Busin said.
“Keratoconus patients suitable for this type of procedure include all patients who are spectacle- or contact lens-intolerant with scarring of the cone limited to the anterior half of stromal thickness,” he told Ocular Surgery News. “I recommend central corneal thickness to be at least 380 µm. K-readings not higher than 60 D are also recommended, but higher values are not an absolute contraindication.”
The technique is contraindicated in patients with corneas thinner than 380 µm or with opacities reaching the posterior half of stromal thickness, he said.
To perform this automated technique, Dr. Busin uses a microkeratome to remove a lamella 250 µm thick and 9 mm in diameter. A suture tension is placed and a donor button 350 µm thick and 8.5 mm in diameter is obtained, he said.
Dr. Busin performed the results obtained in 10 patients operated on with this technique and followed for up to 3 months postoperatively; eight of the patients had follow-up for 6 months. The patients had the following exams: visual acuity, refraction, keratometry and corneal topography. Postop treatment of these patients consisted of a combination of antibiotics and steroids for 6 to 8 weeks and selective suture removal after 3 months, he said.
The patients’ postop visual acuity results were as follows: At 1 month, one patient was 20/100, three were 20/80, two were 20/60, two were 20/50 and two were 20/40. At 2 months, two were 20/80, three were 20/60, three were 20/50, one was 20/40 and one was 20/30. At 6-month follow-up, one patients saw 20/50, two saw 20/30, three saw 20/25 and two saw 20/20.
“Five patients had postop astigmatism 4.5 D or less at 1 month and eight at 3 months. Seven of the eight patients followed to 6 months had postop astigmatism 4.5 D or less at that time,” Dr. Busin said.
Advantages, disadvantages
The advantages of ALK for keratoconus treatment are that it is simple and efficient, patients enjoy fast visual rehabilitation and there are far less immune rejections, Dr. Busin said. Also, PKP is always available as an additional option, if needed, he said.
“The downsides of the procedure include that there is limited experience with it. It is relatively expensive, as a microkeratome is involved, and it is not applicable for stage IV keratoconus,” 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.