JUN 01, 2012
Refractive Mgmt/Intervention
This prospective study in the March issue of Clinical and Experimental Ophthalmology investigated the level of agreement between intended and measured ablation of the wavefront optimize profile corrected by the Wellington nomogram in myopic spherocylindrical corrections and its impact on refractive outcomes. The results suggest that this profile overablates corneal tissue both in photorefractive keratectomy (PRK) and LASIK, but this significantly impacts refractive outcomes only in high myopic spherocylindrical corrections.
The study included 86 patients (86 eyes) undergoing PRK and 86 patients (86 eyes) undergoing LASIK. The authors found significant overablations in both groups (16.7 µ ± 8.5 µ in the PRK group and 11.8 µ ± 18.5 µ in the LASIK group; P < 0.001 for both).
Intended ablation was the primary determinant of this difference, with greater preoperative error and higher intended ablations producing higher differences. PRK corrections of more than 100 µ significantly affected postoperative spherical equivalent, postoperative defocus equivalent, correction index, difference vector and index of success (P = 0.044, P = 0.05, P = 0.019, P = 0.016, P = 0.006, respectively). LASIK corrections greater than 100 µ significantly impacted only postoperative defocus equivalent, difference vector (P = 0.04) and index of success (P = 0.05).
The results suggest that intended ablations above 100 µ, which correspond to intended myopic spherocylindrical corrections of 6.5 D and above, are likely to produce suboptimal results.
The authors recommend further studies to confirm these results and provide the necessary data for optimal ablations for high myopic spherocylindrical errors.