A Correlative Study Of Astigmatism In Compound Myopic Astigmatism Patients With An Excimer Laser

Purpose: To analyze the correlation between total astigmatism,corneal astigmatism and intraocular astigmatism in patients with compound myopic astigmatism undergoing excimer laser surgery and to provide the basis for surgical design for clinical operations such as corneal refractive surgery and refractive lens surgery.Methods: With compound myopic astigmatism patients aged 18 to42 years old,who were treated in the optometry center of the second affiliated hospital of University of South China during 2015 to 2017 were required.A total of 1575 selected subjects,of which 967 were male and608 females.With compound tropicamide eye drops after dilated medical optometry to obtain total astigmatism,Japan’s TMS-4 corneal topography was used to measure the corneal astigmatism.The J0 component(Jackson cross-cylinder value at 180° or 90° axis),J45 component(Jackson cross column at 135° or 45° axis)of total eye,astigmatism and intraocular astigmatism were analyzed by vector analysis,Mirror value)between the correlation.Correlates multiple factors that may affect intraocular astigmatism.Result: 1.After the vector analysis,the values of J0 components of total astigmatism,corneal astigmatism and intraocular astigmatism were 0.230 ± 0.356,0.473 ± 0.362 and-0.243 ± 0.230,respectively.The values of J45 components were-0.010 ± 0.206,0.002 ± 0.218 and-0.012± 0.199,respectively.2.Total astigmatism and corneal astigmatism J0,J45 components were positively correlated(r = 0.794,P = 0.000,r = 0.560,P = 0.000),the linear regression equation were: TJ0 = 0.781CJ0-0.139;TJ45 =0.528CJ45-0.011.3.Total astigmatism was positive related to the corneal astigmatism when corneal astigmatism in 180° axis,90° axis,45° axis,135° axis,and the linear regression equation were: TJ0 = 0.764CJ0-0.127,TJ0 =0.597CJ0-0.205,TJ45 = 0.562CJ45-0.015,TJ45 = 0.466CJ45-0.022,respectively.Intraocular astigmatism were eliminate corneal astigmatism so as to reduce the total astigmatism when corneal astigmatism in 180°axis,45° axis,135° axis,but in 90° axis the intraocular astigmatism will be superimposed corneal astigmatism so that the total astigmatism were increased.4.There was a positive correlation between intraocular astigmatism and total astigmatism J0 and J45(r = 0.297,P = 0.000,r = 0.421,P = 0.000)0.000,r =-0.516,P = 0.000).5.The intraocular astigmatism J0 composition was negatively correlatedwith spherical equivalent(r =-0.149,P = 0.000),and negatively correlated with mean corneal curvature(r =-0.117,P = 0.000).There was a positive ralated to the total eyelid volume(r = 0.176,P = 0.000)and the intraocular pressure(r = 0.075,P = 0.001),but was not ralated to the central corneal thickness(P = 0.051).Intraocular astigmatism J45 components was not ralated to the spherical equivalent,the mean corneal curvature,the intraocular pressure,the central corneal thickness,the total eye volume(P> 0.05).Conclusion: 1.For patients with compound myopic astigmatism undergoing excimer laser surgery,total astigmatism and corneal astigmatism are mainly with the rule astigmatism,but intraocular astigmatism are mainly with the against astigmatism.2.Total eye astigmatism is mainly composed of corneal astigmatism.When the corneal astigmatism is conformal and oblique astigmatism,the intraocular astigmatism acts as a counteracting effect;when the corneal astigmatism is a counter regulation astigmatism,the intraocular astigmatism appears as a superposition effect.3.The astigmatism in patients with low total eye astigmatism is mainly reflected in astigmatism,and the astigmatism in patients with high total eye astigmatism is mainly astigmatism.Contralateral intraocular astigmatism is more common in low myopia than in high myopia.