A correction formula for real intraocular pressure after LASIK for the correction of myopic astigmatism

The authors performed a prospective study to create a correction formula to determine the real intraocular pressure (IOP) after LASIK procedures. The clinical trial comprised 101 eyes of 59 patients (34 women and 25 men) with a mean age of 32 ± 9 years and a mean preoperative spherical equivalent of −6.3 ± 2.2 diopters (D) (range, −3.0 to 11.5 D). After LASIK, the IOP was reduced from a mean of 16.5 ± 2.1 mm Hg (range, 12 to 22 mm Hg) to 12.9 ± 1.9 mm Hg (range, 8 to 16 mm Hg). Univariate regression analysis showed a statistically significant correlation between central corneal thickness (CCT) and IOP (R2 = 0.531, P < .001, and between keratometry and IOP (R2 = 0.584; P < .001). Multiple linear regression analysis showed a combined influence of CCT and corneal curvature on the measured IOP. The authors developed the following formula to calculate real IOP after LASIK: IOP (real) = IOP (measured) + (540-CCT)/71 + (43-K)/2.7 + 0.75 mm Hg. The authors conclude that the measured IOP after LASIK must be corrected to avoid false low IOP applanation measurements.—Michael D. Wagoner