Excimer ablation design and elliptical transition zones.

PURPOSE To describe the rationale behind elliptical and other transition designs used with the excimer laser. SETTING Casey Eye Institute, Oregon Health Sciences University, Portland, Oregon, USA. METHODS Ablation zone designs were analyzed for the number of transition points for myopia and hyperopia. The advantages and disadvantages of elliptical transition zones are demonstrated graphically, with an emphasis on smooth ablation zone design to maximize the optics and biologic tolerance by the eye. RESULTS The use of an individualized elliptical transition maximizes a circular effective optical zone and can enhance the smoothness of the transition zone while minimizing excessive tissue removal. CONCLUSION Elliptical transition zones may improve the optics and biologic tolerance of excimer laser treatments.