Effect of LASIK on non-contact tonometry

Objective To investigate the reason of intraocular pressure (lOP)decrease measuring by non-contact tonometry (NCT)after LASIK for myopia. Methods Six hundreds and sixty myopias underwent LASIK were enrolled in the study. Their data of IOP,central corneal thickness (CCT)and corneal refractive power (CRP) before LASIK and at 3 months were analyzed by SPSS13.0. The same kind data before and after LASIK were evaluated by the paired, 2-tailed t test. Multiple linear regression and correlation analyses were performed. If the correlation coefficient r≥0.4, P<0.001, an linear regression equation is established. Results Postoperative average IOP, CCT and CRP of 660 eyes decreased by (5.01±2.23 )mmHg(t=57.736 P=0.000), (69.4±26.12)μm (t=68.255 P=0.000)and(4.37±1.72)D (t=65.140 P =0.000),respectively. Multiple linear regression equation between IOP, CRP and CCT is Y(IOP)=3.119-0.204X1(CRP)+0.040X2 (CCT), R2=0.251,Sy.x=2.215,preoperatively, and Y (IOP)=1.981-0.017 X1 (CRP)+0.021X2 (CCT),R2=0.277,Sy.x=1.474,postoperatively. CCT reduce every 21μ m, IOP drop 1 mmHg. Conclusions The drop in IOP after lasik formyopia is mainly related to the reduction in CCT. Key words: LASIK; Cornea;  IOP