Corneal intrastromal tissue modeling with the femtosecond laser.

Purpose: To determine whether central corneal thinning and flattening can be achieved by intrastromal photodisruption using a femtosecond (fs) laser.

Setting: Institute of Clinical Neuroanatomy, Goethe-University, Frankfurt am Main, Germany.

Methods: Fourteen horizontal, parallel intrastromal cuts were performed on rabbit eyes using a fs laser. Full-grown rabbits (group 1; ten eyes) received bilateral treatment. Growing rabbits (group 2) received unilateral treatment (four eyes). Slit-lamp examination, pachymetry, and keratometry were performed on day 9, 31 and 86 (group 1) or on day 12, 29, 69, 176 and 318 (group 2) after surgery.

Results: Nine days after treatment, corneal swelling was present and a slight increase of mean corneal thickness (group 1: +4.40 ± 5.56 μm) as well as a steeper mean corneal curvature (group 1: -0.18 ± 0.02 mm) were observed. In contrast, 1 month after tissue photodisruption corneas showed an average decrease of thickness (group 2: -21.0 ± 2.5 μm). By 6 months post-treatment, a further decrease (group 2: -36.3 ± 6.9 μm) was seen that remained stable for the rest of the observation period. At 176 days post-treatment, a decrease of corneal curvature (group 2: -0.21 ± 0.10 mm) was found. Slit-lamp examination revealed a transparent cornea. At the site of intrastromal photodisruption a narrow band of increased reflectivity could be detected.

Conclusions: Corneal thinning can be reliably achieved using intrastromal tissue modeling with a fs laser. Tissue modeling was accompanied by a transient opacity and irregularity of the corneal surface.