JUL 07, 2009
The authors of this study used TOSCA II (Topography Supported Custom Ablation) with the MEL 80 excimer laser and CRS-Master software platform (Carl Zeiss Meditec) to treat 48 eyes of 32 patients with high corneal aberrations and refractive errors following previous ocular surgery. The results indicated that TOSCA II treatment appears to be effective for decentrations, optical zone enlargement and reduction of higher order aberrations following previous refractive surgery with unsatisfactory outcomes, as well as topographic irregularity associated with corneal transplantation. However, the authors concluded that it was less effective for other types of irregularly irregular astigmatism, including corneal scars, postoperative cataract wound gape (incisional) and postoperative conductive keratoplasty irregularities.
The TOSCA II algorithm is designed to smooth corneal irregularities, control refraction to a specified target and induce fewer aberrations while correcting residual refractive error. All treatments were performed by one surgeon at one clinic over a 22-month period. Seven patients (14 eyes) required retreatment after primary surgery for high myopia at the clinic. Twenty-five patients (34 eyes) self-referred due to difficulties linked to irregular astigmatism following refractive surgery at other locations.
The patients presented with problems, including small optical zone, decentered ablation, subjective visually significant higher order aberrations, wound gape following cataract surgery, irregular high myopic or mixed cylinder induced after deep lamellar keratoplasty, and irregularly irregular astigmatism induced by LASIK, photorefractive keratectomy, radial keratotomy or conductive keratoplasty. In patients with residual myopia, TOSCA II was used to optimize the size of the optical zone and reduce aberrations induced by the previous procedures.
Median follow-up was 9.4 months. Seventy-seven percent of eyes (37/48) obtained results within 1.00 D of intended correction and 60 percent (29/48) within 0.50 D. The average higher order root-mean-square decreased significantly by 21 percent and the average spherical aberration decreased significantly by 41 percent. Mean logMAR UCVA improved significantly from 0.220 to 0.069. Significant improvement in contrast sensitivity was seen in eyes with below-normal contrast sensitivity preoperatively.
Dr. Stahl is a consultant for Alcon Laboratories, Inc., and Bausch & Lomb Surgical.