Corneal tunnel creation with laser simple, effective

November 1, 2007

Creating channels using a femtosecond laser (IntraLase FS, IntraLase Corp.) to insert a corneal implant (Intacs, Addition Technology Inc.) has some advantages, but the procedure also has the potential for complications. Both are detailed.

Key Points

Istanbul, Turkey-Creating corneal tunnels using a femtosecond laser (IntraLase FS, IntraLase Corp.) to insert a corneal implant (Intacs, Addition Technology Inc.) to treat keratoconus is simple and effective, according to Efekan Coskunseven, MD.

"Creating channels using [femtosecond laser] has some advantages: stable depth up to 400 μm, adjustable channel width, short surgical time of 6 to 8 seconds, and the surgery is simple to perform, comfortable, and effective for patients. However, patients with keratoconus should be informed about the potential for complications," he concluded.

Surgeons, however, should be aware of possible complications associated with the procedure, he added. These include, migration of the segments, vascularization of the wound, corneal melting, and exposure of the segments.

Dr. Coskunseven, director, refractive surgery department, Dunya Eye Hospital, Istanbul, Turkey, discussed results of a study enrolling 300 eyes in 200 patients with keratoconus. Patients were aged 18 to 50 years. To be included in the study, patients had to have grade 1, 2, or 3 keratoconus; be aged more than 18 years; have eyes that could not tolerate contact lenses; and have corneal thickness of at least 350 μm at the thinnest point and at least 450 μm at the site of the incision.

Patients were followed postoperatively on days 1, 7, 30, and 90, and then every 6 months. At the follow-up examinations, the uncorrected and the BCVA levels were recorded. Topography (Orbscan IIz, Bausch & Lomb; Allegretto Wave Topolyzer, WaveLight) and ultrasound pachymetry (CorneoGage Plus, Sonogage) were performed.

Segments implanted superiorly were larger than those used inferiorly.

Creating channels

Using the laser, the time to create channels was about 8 seconds. The length of the incision was 1 mm, and the depth was 75% of the corneal thickness measured at 7 mm and up, to 400 μm. The incision site chosen was the steep meridian.

"Implantation was harder than when done mechanically because, in this surgery, the channel width was 0.35 mm," he said.

All surgeries were performed with patients under topical anesthesia. One 10-0 nylon suture was placed at the end of the procedure. Dr. Coskunseven said he believes that a "U suture technique" can be effective to stop migration of the segments.

"When we analyzed the uncorrected visual acuity [UCVA], there was a one-to two-line loss of vision in 4.6% of eyes," Dr. Coskunseven reported. "The visual acuity remained unchanged in 9% of eyes. There was a one-to two-line gain in 32% of eyes; 46% of eyes had a gain of three to five lines; 8% of eyes had a six-line or greater gain in vision. In this study, lines of UCVA gained was seen in more than 85% of the eyes."

A one-to two-line loss of BCVA occurred in 13.3% of the eyes, he said. The BCVA did not change in 25% of the eyes. There was a one-to two-line gain in 32%, a three-to five-line gain in 26%, a 6-line or greater gain in 2.6%.

"More than 60% of eyes had a gain in BCVA in this study," Dr. Coskunseven stated.

The mean UCVA increased from 0.12 preoperatively to 0.38 postoperatively, and the mean BCVA increased from 0.42 postoperatively to 0.55 postoperatively. The mean spherical equivalent decreased from –6.5 D preoperatively to –2.02 D postoperatively. The mean K-readings decreased from 48.7 to 44.2 postoperatively.

Complications

Several complications were associated with the procedure. The segments migrated in 14 eyes (4.6%), vascularization of the wound developed in three eyes (1%), corneal melting and exposure of the segments was seen in 17 eyes (5.6%), and the segments had to be explanted in 20 eyes (6.6%), according to Dr. Coskunseven.