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Corneal topography after excimer laser photorefractive keratectomy for myopia
S D Trocmé1, K A Mack, K S Gill
1Department of Ophthalmology and Visual Sciences, Galveston 77555-0787, USA.
Background:
This study was performed to assess and correlate the changes in central corneal power with the changes in manifest refraction after myopic photorefractive keratectomy (PRK) and to measure ablation zone centration.
Methods:
Fourteen patients had computerized videokeratography and manifest refraction performed preoperatively, and than 1, 2, 3, 4, 6, and 12 months after photorefractive keratectomy.
Results:
There was a significant association (r = -0.9; p < 0.0001) between changes in manifest refraction and changes in central corneal power at the 12-month postoperative examination; however, a mean difference of 1.1 D was seen between the two readings. The mean decentration of the ablation zone was 0.47 +/- 0.26 mm (range, 0.08 to 1.05 mm: 0 to 0.49 mm, six patients; 0.50 to 0.99 mm, seven patients; and 1.00 to 1.50 mm, one patient).
Conclusions:
Corneal power-as measured by videokeratography-is not an accurate predictor of manifest refraction, although the two parameters did demonstrate good correlation. Centration of ablations was comparable to previous studies.