Clinical Study On Changes Of NCT Measurement Value After SMILE In Patients With Myopia

Objective:To study changes of the normal intraocular pressure?IOP?fluctuation range after the small incision lenticule extraction?SMILE?in patients with myopia and to explore new methods for postoperative IOP(IOP_post)correction.Methods:In this prospective case series study,76 patients?152 eyes?who underwent SMILE at the Affiliated Hospital of Qingdao University from May 2018 to May 2019 were involved,and they were divided into low myopia???,moderate myopia???,and high myopia???groups.The 24-hour IOP measured by non-contact tonometry?NCT?,spherical equivalent?SE?,central corneal thickness?CCT?,corneal curvature,the horizontal corneal diameter?WTW?,corneal volume?CV?,the central 3-mm diameter CV(CCV_3mm),CCV_{3 mm}/CV,the cutting CV??CV?and?CV/CV were measured on 3 days preoperatively and 6 months postoperatively.The 24-hour IOP changes in both eyes and every groups were observed preoperatively and postoperatively.The correlation between the postoperative NCT measurements(NCT_post)and various factors was statistically analysed,and the IOP_post expression model was established by phased multiple linear regression analysis.Results:1.The average IOP_pre in the three groups were 16.25±2.14mmHg?15.91±1.88mmHg?16.74±2.21mm Hg,and the differences were statistically significant in each group?F=12.124,P<0.001?.The average IOP_post were 10.64±1.71mm Hg?10.33±1.6mmHg?10.18±1.62mm Hg,and the differences were statistically significant in each group?F=5.715,P=0.003?.The IOP_pre intervals were 11.7?20.3mm Hg,10.0?19.0mmHg,12.0?20.0mm Hg,and the IOP_post intervals were 8.0?16.0mmHg,7.0?15.3mmHg,7.0?14.0mm Hg.Compared with the IOP_pre,the IOP_post is smaller in value and more concentrated in distribution.2.The trend curves of the average IOP value at each time point of 24 hours before and after SMILE in each group were higher at night and morning,and lower at afternoon and evening.The most of the IOP peaks before and after surgery appeared at 18:00-6:00,and the most of the IOP troughs before and after surgery appeared at 14:00-22:00.3.The average circadian IOP differences before and after operation in group?were 3.91±1.16mmHg and 2.91±0.84mmHg respectively.The paired T test showed that the differences were statistically significant?T=4.44,P<0.001?.The average circadian IOP differences before and after operation in group?were 3.42±1.09mmHg and 2.74±0.90mmHg respectively.The paired T test showed that the differences were statistically significant?T=3.64,P=0.001?.The average circadian IOP differences before and after operation in group?were 3.61±1.45mm Hg and 2.56±1.01mmHg respectively.The paired T test showed that the differences were statistically significant?T=3.68,P=0.001?.The circadian IOP_pre difference intervals in each group were 1.0?6.3mmHg,2.0?7.4mm Hg and 1.3?7.0mm Hg.And the postoperative ones were 1.3?4.4mm Hg,0.6?5.0mm Hg and1.0?5.0mmHg,respectively.Compared with the circadian IOP_pre differences,the circadian IOP_post differences were smaller in value and more concentrated in distribution.4.The mean IOP differences between the eyes before and after SMILE were respectively2.16±1.48mmHg and 1.70±1.24mm Hg,the differences were statistically significant?t=5.177,P<0.001?;the mean IOP difference intervals between the two eyes before and after the operation were 0.0?5.0mm Hg and 0.0?4.0mmHg,respectively.The binocular IOP_postost differences were narrower than the preoperative ones and the distributions were moreconcentrated,the diurnal variations of IOP and binocular differences were irrelevant?F1=1.322 F2=0.257,P1=1.195 P2=0.311?.5.The IOP_post corrected by the Ehlers method after SMILE in group?was lower than the IOP_pre,and the difference was statistically significant?t=3.716 P<0.001?.The IOP_postost corrected by the Ehlers method in?group was statistically higher than that before the operation?t=-2.088 P=0.038?.There was no statistically significant difference between the IOP corrected by the Ehlers method after SMILE in group III and the preoperative IOP(IOP_pre)?t=-1.748,P=0.082?.The NCT_post and the IOP_post corrected by Pentacam?Shah,Dresden,Kohlhaas,Orssengo/pye?in the other groups were significantly and statistically lower than the IOP_pre?P<0.001?.6.The IOP_post in each group was positively correlated with IOP_pre,postoperative CCT(CCT_post),3mm/WTW,postoperative CV(CV_post),postoperative CCV_{3 mm}(CCV_post3mm),and CCV_post3mm/CV_post?P<0.05?,and had negative correlation with WTW?P<0.05?.There was no significant correlation between the IOP_post and the postoperative corneal curvature(corneal curvature_post),?CV?P>0.05?.7.Perform the regression analysis of influencing factors and establish a staged multiple regression model:NCT_{post corrected???}=0.432×NCT_post+3.419×CCV_post3mm-0.679×WTW+7.637?F=76.442,P<0.01?,adjusted R²=0.457;NCT_{post corrected???}=0.552×NCT_post+2.184×CCV_post3mm+0.127×CV_post-4.462?F=128.204,P<0.01?,adjusted R²=0.515;NCT_{post corrected???}=0.721×NCT_post+3.505×CCV_post3mm-2.123?F=126.737,P<0.01?,adjusted R²=0.539.Conclusion:1.The interval of the distribution of IOP measured values,the binocular difference and the range of diurnal IOP fluctuations after SMILE were smaller than those of the preoperative IOP measured values.2.The corneal volume change with a central diameter of 3 mm can be used as an important reference index for the calculation and correction of IOP after SMILE,used to estimate the IOP value after SMILE,so as to provide a reference for screening,diagnosis and treatment of potential glaucoma patients.