Correlation Analysis Of Area Of Corneal Invasion Of Pterygium And Measurement Diviation With Intraocular Lens Power

Objective:To investigate the correlation between area of corneal invasion of pterygium and measurement deviation with intraocular lens power.To provide references for clinical work and operation timing.Methods:According to the exclusion and inclusion criteria,a prospective study was conducted on 22 pterygium patients(a total of 33 eyes)who were admitted to Shenzhen Second People’s Hospital from November 2018 to December 2020.The length of pterygium invasion into the cornea and the width of the corneal limbus of each patient were measured,and then the area of pterygium invasion into the cornea was calculated.The specific methods were as follows:(1)Length(mm):the distance from the top of the pterygium head to the corneoscleral margin was measured with a angle gauge under a slit lamp;(2)Width(mm):the distance between the two endpoints of the pterygium on the angular margin was measured.(3)Area(mm2):length*width/2=area.Vertical and horizontal K values(D)and anterior chamber depth ACD(mm)were measured by OrbscanⅡ anterior segment analyzer,and vertical and horizontal K values(D),anterior chamber depth ACD(mm)and axial length AL(mm)were measured by IOL-Master500.Then the patients were divided into three groups according to the length of pterygium invasion into the cornea,the width of the corneal limbus and the area of the pterygium:Group a(≤2 mm)with 12 eyes,Group b(between 2mm to 5mm)with 16 eyes and Group c(>5 mm)with 5 eyes.The width of pterygium invasion into the cornea was divided into three groups according to the width of pterygium invasion into the cornea.The width of pterygium invasion into the cornea was ≤4 mm was Group① with 9 eyes,and the width of pterygium invasion into the cornea was 4 mm-6 mm was Group② with 18 eyes,and the width of pterygium invasion into the cornea was>6 mm was Group③ with 6 eyes.According to the area of pterygium invasion into the cornea,the patients were divided into four groups:group Ⅰ(≤5 mm2)with 5 eyes,group Ⅱ(between 5mm2 to 10mm2)with 6 eyes,group Ⅲ(between 10mm2 to 15mm2)with 14 eyes and group Ⅳ(>15mm2)with 8 eyes.Collected each measured value of vertical and horizontal K(D),anterior chamber depth ACD(mm),axial length AL(mm),using appropriate statistical analysis method after comparison between the groups abc,groups①②③and groupsⅠ Ⅱ Ⅲ Ⅳ(vertical and horizontal K value,anterior chamber depth,the axial length AL,ACD);the differences of the data are processed by Excel software to establish a database,SPSS 20.0 software and statistical methods were used to compare and analyze the data measured by IOL-Master500 and OrbscanⅡ in the above groups(groups abc,①②③,Ⅰ Ⅱ Ⅲ Ⅳ).All groups(groups abc,①②③,Ⅰ Ⅱ Ⅲ Ⅳ)were represented by means of mean value(x±s)by IOL-Master500 and OrbscanⅡ.The differences of mean value between groups was tested by F test,namely one-way ANOVA.The corneal horizontal K values,vertical K values and anterior chamber depth measured by OrbscanⅡ and IOL-Master500 were compared by paired t-test.P<0.05 was considered statistically significant.Finally,the corresponding conclusions are drawn according to the statistical analysis results.Results:With the increasing of the length and width of pterygium invasion into the cornea,when the length of pterygium invasion into the cornea were ≤ 2 mm and the width of pterygium invasion into the cornea were ≤4 mm,the horizontal K value measured by IOL-Master500 was the highest.When the length of pterygium invasion into the cornea was between 2mm to 5mm and the width of pterygium invasion into the cornea was between 4mm to 6mm,the horizontal K value measured by IOL-Master500 was the smallest.When the length of pterygium invasion into the cornea was>5 mm and the width of pterygium invasion into the cornea was>6 mm,the anterior chamber depth(ACD)measured by IOL-Master500 was the highest.When the length of pterygium invasion into the cornea was between 2mm to 5mm and the width of pterygium invasion into the cornea was between 4mm to 6mm,the value of anterior chamber depth(ACD)measured by IOL-Master500 was the smallest.The above differences were significant(P<0.05).In this study,we also found that the anterior chamber depth measured by IOL-Master500 was larger than that measured by OrbscanⅡ anterior segment analyzer,and the difference was statistically significant(P<0.05).Conclusion:For cataract patients with pterygium,when the length of pterygium is less than 2mm or the width is less than 4mm,before cataract surgery,IOL-master and corneal topography should be performed to measure the patient’s corneal curvature(pay special attention to the K values of the horizontal corneal curvature of the patients)to ensure the accuracy of the calculation of intraocular lens power.If the length of pterygium invasion into the cornea and the width of pterygium invasion into the cornea develop further(the length of pterygium invasion into the cornea was>2mm or the width of pterygium invasion into the cornea was>4mm),pterygium excision should be performed first,and the intraocular lens power should be measured after the stabilization of corneal epithelial repair about 1 month after the operation,and the intraocular lens power should be calculated based on the IOL-Master measurement data.