ANALYSIS OF ASTIGMATIC KERATOTOMY WITH A 5.0-MM OPTICAL CLEAR ZONE

PURPOSE: To investigate the surgically induced refractive change after astigmatic keratotomy with a 5.0-mm optical clear zone in patients wi th severe naturally occurring astigmatism. METHODS: We analyzed surgic ally induced refractive change in 40 consecutive eyes undergoing astig matic keratotomy with a 5.0-mm optical clear zone. The surgically indu ced refractive change was calculated according to the method of Hollad ay, Cravy, and Koch with some modifications. Eyes were divided into tw o groups: Group I included eyes with mixed astigmatism and a maximum p reoperative spherical equivalent of +1.25 diopters that underwent arcu ate keratotomy, and Group II included eyes with compound myopic or sim ple myopic astigmatism (maximum preoperative spherical equivalent of - 3.00 diopters) or mixed astigmatism with low minus spherical equivalen t that underwent four-incision radial keratotomy and arcuate keratotom y. RESULTS: After refractive surgery, all eyes experienced a reduction of astigmatism when examined three months or more after surgery. Only one eye from each group was overcorrected. The magnitude of refractiv e astigmatism of surgically induced refractive change was 3.25 +/- 0.9 0 diopters for eyes in Group I and 3.25 +/- 0.80 diopters for eyes in Group II. There was minimal axis deviation. Eyes in Group I had more f lattening with the wound than steepening against the wound, with a cou pling ratio of -0.86 a 0.36, whereas in Group II, there was flattening both with the wound and against the wound. The net effect of surgery (sum of the primary and secondary effects) was more flattening than st eepening in Group I eyes, and flattening of the circumference of the e ye in Group II. A decrease of one line of best-corrected visual acuity was observed in one (6.6%) of 15 eyes in Group I and in two (8%) of 2 5 eyes in Group II. CONCLUSIONS: A 5.0-mm optical clear zone arcuate k eratotomy is an effective method for correcting moderate to severe nat urally occurring astigmatism. Further investigation of this optical cl ear zone size on glare and contrast sensitivity testing is necessary a nd is underway.