Effect Of Pterygium On The Calculation Of Intraocular Lens Power And Analysis Of Related Factors

Objective:To evaluate the effect of pterygium on the IOL power by bioassay,analyze the relevant factors,and select a more appropriate operation time for patients with pterygium comPlicated with cataract and reduce the error of the degree of intraocular lens before cataract combined with pterygium resection.Methods:A total of 34 patients with pterygium in the ophthalmology department of yijishan hospital from May 2017 to August 2018 were selected(according to the established inclusion and exclusion criteria),including 34 pterygium eyes(study group)and 34 healthy eyes(control group).All patients were treated with pterygium excision and limbal stem cell autograft transplantation.The length and width of the cornea invaded by pterygium were measured preoperatively,the area was calculated,and the best corrected distance visual acuity(BCDVA),corneal astigmatism,corneal curvature radius,corneal curvature,axial length,anterior chamber depth,and intraocular lens degree(SK-T、SK-Ⅱ)of both eyes were collected and analyzed preoperatively and three months after surgery.SPSS 20.0 was used for statistical analysis.Results:1.There were significant differences in the BCDVA,corneal astigmatism,horizontal corneal curvature radius,average corneal curvature radius,horizontal corneal curvature,average corneal curvature,and intraocular lens power(SK-T、SK-Ⅱ)measured before and 3 months after surgery or both eyes before surgery in the study group(P<0.05).There were no significant changes in corneal vertical curvature radius,corneal vertical curvature,anterior chamber depth and axial length(P>0.05).2.The degree of corneal astigmatism before surgery is positively correlated with the length,width and area of pterygium(P<0.05).The postoperative astigmatism is positively correlated with the length of pterygium(P<0.01).3.In the study group,the critical point for the diagnosis of whether pterygium has an effect on the cornea is the preoperative astigmatism of the cornea-1.130D.The difference of corneal astigmatism in both eyes before surgery-0.625D is the critical point to evaluate whether pterygium has an effect on corneal astigmatism.4.The horizontal curvature and mean curvature of the cornea are positively correlated with the length,width and area of pterygium.The length of 2.51mm,the width of5.50mm and the area of 6.77mm~2 are the critical points to evaluate the effect of pterygium on the horizontal curvature of the cornea.5.There were statisticant differences in the preoperative SK-T and SK-Ⅱformula for the calculation of IOL power(P<0.01),and there were no significant difference after operation.There were no statistical difference in the SK-T and SK-Ⅱformula of preoperative and postoperative IOL power difference,and also no difference in the IOL power difference of both eyes after operation(P>0.05).6.The difference of IOL power between both eyes before surgery 0.25D and the difference of IOL power before and after surgery 0.25D are the critical points to evaluate whether pterygium has an effect on the determination of IOL power.7.When the length of pterygium is greater than 2.78mm,the width is greater than5.60mm,and the area is greater than 7.38mm~2,the deviation in the calculation of IOL power is at least equal to or greater than 0.5D.Conclusion:1.Pterygium could cause the decrease of vision,corneal curvature,the increase of corneal astigmatism,and increase the error of IOL power determination.2.A larger pterygium could cause differences in the corneal horizontal curvature,which could further affect the determination of IOL power.3.Corneal astigmatism before surgery,the difference of corneal astigmatism in both eyes before surgery,the difference of IOL power in both eyes before surgery and the difference of IOL power before and after surgery can provide reference for choosing the operation time of pterygium patients with cataract.4.IOL power and related factors are positively correlated with the size of pterygium.5.If the pterygium size is larger than 2.40mm,5.60mm or 7.38mm~2 and simultaneous surgery is planned,the implanted IOL power should be at least 0.50 D smaller than the calculated power.