Corneal intrastromal tissue modeling with the femtosecond laser

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

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

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.

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.

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.