Excimer ablation design and elliptical transition zones

Purpose: To describe the rationale behind elliptical and other transition d esigns 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 p oints for myopia and hyperopia. The advantages and disadvantages of ellipti cal transition zones are demonstrated graphically, with an emphasis on smoo th ablation zone design to maximize the optics and biologic tolerance by th e eye. Results: The use of an individualized elliptical transition maximizes a cir cular effective optical zone and can enhance the smoothness of the transiti on zone while minimizing excessive tissue removal. Conclusion: Elliptical transition zones may improve the optics and biologic tolerance of excimer laser treatments. (C) 1999 ASCRS and ESCRS.