Efficacy Analysis Of The Regression Formula About Factors That Influence The Intraocular Pressure Of Noncontact Tonometer Following Myopic Lasik

Purpose To establish and validate the regression formula of noncontact intraocular pressure by analyzing the influencing factors of intra-ocular pressure following laser assisted in situ keratomileusis（LASIK）.Methods A prospective case study was performed on 235 myopia patients who had receiving LASIK in the department of Ophthalmology and Optometry center of the second affiliated hospital of University of South China during January 2015 to March 2016.After self-contrast of randomized paired design,the influencing factors of intraocular pressure measured by noncontact tonometer(IOP_NCT)were analyzed.The multiple regression formula for forecasting the changes of IOP_NCT after LASIK was established and verified.Results 1.The average intraocular pressure measured by noncontact tonometer of pre-LASIK and 3 months post-LASIK myopic patients,were16.88 mmHg and 11.62 mmHg,respectively.The intraocular pressure were experienced a mean decline of 5.26 mmHg.2.There were no statistical significant differences between which side eye and age groups of the intraocular pressure measured by noncontact tonometer of perioperative period in LASIK,while statistical significance was found between genders.The male reported higher intraocular pressure than the female.There were statistical significant differences between preoperative and postoperative of the intraocular pressure measured by noncontact tonometer,while no statistical significance was found between 1month and 3 months post LASIK.3.The pre-LASIK IOP_NCT was not related to the average keratometry（P>0.05）,but slightly positive correlated with the absolute value of the spherical equivalent,and medium positive correlated with the central corneal thickness（CCT）.By stepwise regression analysis,a regression formula was given:Preoperative IOP_NCT=CCT×0.041-5.582（R²=0.140,P<0.01）…………………………………………Formula（1）4.The change of IOP_NCT(△IOP_NCT)before and 3 months after myopic LASIK,which was not related to the average keratometry or the stroma bed thickness,was positive related to the preoperative IOP_NCT,the central corneal thickness,the absolute value of the spherical equivalent,the ablation depth and the ablation rate（AR）.On this base,several multiple regressive models were obtained:⑴△IOP_NCT=Preoperative IOP_NCT×0.572-4.388（R²=0.496,P<0.001）……………………………………………Formula（2）⑵△IOP_NCT=Preoperative IOP_NCT×0.552+AR×0.158-6.219（R²=0.561,P<0.001）……………………………………………Formula（3）⑶△IOP_NCT=Preoperative IOP_NCT×0.587+AR×0.168-CCT×0.011-1.103（R²=0.573,P<0.001）…………………………………Formula（4）5.The verification shows that the estimated values of the change of IOP_NCT calculated by the 3 formulae above were not significantly different from the actual measured values（all P>0.05）.Conclusions 1.The intraocular pressure measured by noncontact tonometer of the perioperative period of myopic LASIK,which would be affected by neither left or right eye nor by different age groups,was slightly higher in males.The measured intraocular pressure decreased to a stable state after 3 months postoperative,and decreased by 5.26 mmHg compared with the preoperative mean value.2.The pre-LASIK IOP_NCT was not related to the average keratometry,but positive correlated with the central corneal thickness and the absolute value of the spherical equivalent.The change of IOP_NCT before and 3 months after myopic LASIK,which was not related to the average keratometry and the stroma bed thickness,was positive related to the preoperative IOP_NCT,the central corneal thickness,the absolute value of the spherical equivalent,the ablation depth and the ablation rate.3.This paper established some regression formulae on noncontact intraocular pressure changes after myopic LASIK.The formulae checked by the actual cases could be used to predict the changes of IOP_NCT before and 3months after myopic LASIK.