توپوگرافي قرنيه بعد از جراحي برشهاي شعاعي قرنيه

Corneal Topography after Radial Keratotomy

Background and Objectives: Radial keratotomy is one of the current techniques in correction of myopia which has high prevalence in general population. The main purpose of this study was to evaluate changes in pattern and profile of corneal topography before, one week and third months after surgery. Secondary aims of this study were to record the subjective complaints and their correlation with topographic changes after surgery. Materials and Methods:In a clinical trial, comparison of corneal topography before and after RK was done in 50 eyes of 26 patients from 19/3/1997 to 20/9/2001. In all patients, routine eye examinations were performed before surgery along with determination of pattern and profile of corneal topographies (asphericity coefficient). Surgery were done under topical anesthesia with 0.2 mm diamond knife. Incision technique was as the American method with present standard nomograms. Corneal topography in first week and third months after surgery was done with special attention to central optical zone (COZ) pattern, presence of multifocality and asphericity coefficient. Patientʹs complaints also were recorded. Results: The mean age of patients was 29 (18-60) years. 74% out of patients were male and 26% female. The mean duration of follow up was 10.5 months. The most common patterns of topography before surgery were asymmetric bow-tie (44%), symmetric bow-tie (40%), and spheric (8%). Corneal profile was prolate in 92% and spheric in 8% of cases. No case of oblate profile was found before surgery. Prevalent corneal patterns after surgery were regular polygonal (circular or elliptic) in 50% , Band like in 22%, and split in 28% of cases. Corneal multifocality was found in 38% of cases after surgery. Corneal profile was oblate in 94% and prolate in 6% of cases. Conclusion: Radial keratotomy induces various changes in corneal pattern and profile after surgery. Increased corneal asphericity and switching from prolate to oblate profile were noted. MultifocaIity in central flat zone can increase uncorrected visual acuity without considerable optical complications. Split pattern of central optic zone can cause diurnal fluctuation of vision.