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Analysis of astigmatic keratotomy with a 5.0-mm optical clear zone
S Chavez1, A Chayet, L Celikkol
1Department of Ophthalmology, University of California, San Diego School of Medicine, La Jolla 92093-0684, USA.
Purpose:
To investigate the surgically induced refractive change after astigmatic keratotomy with a 5.0-mm optical clear zone in patients with severe naturally occurring astigmatism.
Methods:
We analyzed surgically induced refractive change in 40 consecutive eyes undergoing astigmatic keratotomy with a 5.0-mm optical clear zone. The surgically induced refractive change was calculated according to the method of Holladay, Cravy, and Koch with some modifications. Eyes were divided into two groups: Group I included eyes with mixed astigmatism and a maximum preoperative spherical equivalent of +1.25 diopters that underwent arcuate keratotomy, and Group II included eyes with compound myopic or simple myopic astigmatism (maximum preoperative spherical equivalent of -3.00 diopters) or mixed astigmatism with low minus spherical equivalent that underwent four-incision radial keratotomy and arcuate keratotomy.
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 refractive astigmatism of surgically induced refractive change was 3.25 +/- 0.90 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 flattening with the wound than steepening against the wound, with a coupling ratio of -0.86 +/- 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 steepening in Group I eyes, and flattening of the circumference of the eye 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 25 eyes in Group II.
Conclusions:
A 5.0-mm optical clear zone arcuate keratotomy is an effective method for correcting moderate to severe naturally occurring astigmatism. Further investigation of this optical clear zone size on glare and contrast sensitivity testing is necessary and is underway.
