Clinical relevance of radius of curvature error in corneal power measurements after excimer laser surgery.

PURPOSE

To compare central and paracentral corneal curvature measurements after myopic excimer laser surgery performed using a large optical zone (OZ) (6.5mm).

SETTING

Private practice.

METHODS

The mean simulated keratometry (SimK) value, average central power, corneal power of Placido rings 1 to 9 and the average central corneal power over the central 3.0mm (ACCP(3mm)) were measured using a TMS-2 corneal topographer.

RESULTS

Forty-two patients (mean correction -5.0 diopters [D]+/-2.2 [SD]) were prospectively enrolled. The mean SimK value (38.82 D+/-1.95) and the mean average central power (38.89+/-2.02 D) were not statistically significantly different, even when the sample was stratified according to the amount of induced correction (lower or higher than -5.00 D). The difference between the central and paracentral measurements was statistically significant when considering the ACCP(3mm), whose mean value was lower than the SimK value in eyes with a myopic correction less than -5.00 D (mean 39.53+/-1.92 D versus 39.67+/-1.82 D) (P=.0013) and in eyes with a myopic correction greater than -5.00 D (37.64+/-1.75 D versus 37.9+/-1.69 D) (P<.0001).

CONCLUSIONS

In eyes with a large OZ, the clinical relevance of the radius error was limited, especially with myopic corrections less than -5.00 D. The mean difference between central and paracentral corneal curvature data, although more evident, was still relatively small, even in eyes that were treated for more than -5.00 D of myopia.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.