Analysis Of The Change Of Intraocular Pressure Befor And After Laser In Situ Keratomileusis

Objective:To explore the related influential factors about the value of intraocular pressure measured by non-contact tonometer in myopic people and the changes about intraocular pressure(IOP) before and after laser in situ keratomileusis(LASIK) and the correlated influential factors.Methods:In 3325 myopic patients which will be treated with laser in situ keratomileusis(LASIK),the data of 3325 right eyes and 277 cases with anisometropia in both eyes was achieved and analyzed with T-test,variance,and statistics of relativity.The investigation includes a lot of factors,such as central comeal thickness (CCT),corneal curvature,axis oculi ength,age,sex,diopter and anisometropia and so on.To explore the relation between these influential factors and IOP(intraocular,measured by non-contact tonometer).Then choose 164 patients(164 right eyes) from above-mentioned 3325 myopic patients,which have been treated with LASIK.The intraocular pressure measured by non-contact tonometer,central comeal thickness(CCT), comeal curvature have been measured before and one month and three month after LASIK.Then analysis these measured values.Results:Before LASIK the mean value of IOP is 16.21mmHg±2.73 mmHg (1mmHg=0.133kpa);the mean value of CCT is 541.36μm±28.47μm,IOP is related with CCT,the coefficient r=0.4768;the mean value of curvature of cornea is 44.52Dμ1.11D,which is related with IOP,the coefficient r=0.1010.The IOP is becoming low with the age increasing.When the age≤20,the mean value of IOP is 16.52mmHg±2.86mmHg,21～29,the mean value of IOP is 16.20mmHg±2.84mmHg, the age 31～40,the mean value of IOP is 16.08mmHg±2.84mmHg.Statistice difference appeared in the analysis of variance with the 3group(F=4.4996, p=0.0112).IOP will go up with the increase of diopter,diopter≤3.00D,the mean value of IOP is 16.08mmHg±2.87mmHg;diopter3.25D～6.00D,the mean value of IOP is t6.20mmHg±2.90 mmH;diopter6.25D～9.75D,the mean value of IOP is 16.46mmHg±2.79 mmHg;diopter≥10.00D,the mean value of IOP is 16.84±2.77 mmHg.Statistice difference appeared in the analysis of variance with the 4 group (F=19.6636,p=0.0001).There is not associativity between the value of Intra ocular pressure in myopic people and axis oculi,sex.IOP in myopic which has anisometropia in both eyes is idem(p=0.5637),there is no statistic difference.There is a significant correlation between IOP and CCT pre-LASIK(r=0.4768;p=0.0001). After LASIK the mean value of IOP is 8.97 mmHg±2.34 mmHg (1mmHg=0.133kpa);the mean value of CCT is 452.63μm±29.52μm,IOP is related with CCT,the coefficient is r=0.3221,p=0.0001;corneal curvature 38.89D±1.23D,the coefficient related with IOP is r=0.2032,p=0.0001;This correlation was also found between the changes in IOP and ablation depth of CCT post-LASIK the coefficient is r=0.4139;p=0.0001;the coefficient between the changes in IOP and the changes c in orneal curvature is r=0.2865,p=0.0001.Conclusions:Before LASIK the mensure of IOP is associated with CCT and curvature of cornea.Intraocular tension is becoming low with the age increasing.Intraocular will go up with the increase of diopter.IOP is not related with axis oculi,and sex.IOP is not different in both eyes with anisometropia.Central conceal thickness and conceal curvature are important factors in measuring IOP by NCT.The decrease in IOP after Lasik was related to the decrease in CCT.With the change of the corneal thickness,the value of measuring IOP will have corresponding change.So corneal thickness should be considered in precise measurement, particularly in eyes with previous photorefractive surgery.