Clinical Study On Surgical Correction Strategies Of Different Degrees Of Astigmatism

BackgroundAstigmatism refers to a refractive state in which eyeballs have different refractive powers on different meridians,and two focal lines and the circle of least confusion at different positions in the space are formed after a parallel light is refracted by the eyeball.Astigmatism not only affects visual quality,but also reduces the ability to perform tasks with high visual demands.With the development of refractive surgery,more and more people choose surgery to correct astigmatism.At present,intraocular surgery such as Toric ICL or Toric IOL or corneal ablation such as FS-LASIK,SMILE and non-corneal ablation such as LRIs,AK,etc.are often used for moderate and high astigmatism correction.Intraocular surgery and corneal ablation are different in terms of surgical principles,techniques and design.There are few literature reports on the comparison of the effects of astigmatism correction between the two surgical methods,and there is no relevant clinical research basis.Corneal ablation is often used for low astigmatism correction.However,if there is axial deviation when low astigmatism is corrected,not only does it fail to correct astigmatism effectively,but it also creates new astigmatism.In addition,individual tolerance to astigmatism is different.For patients who have been used to low astigmatism for a long time,it may be more conducive to their rapid recovery after surgery if the physiological astigmatism is maintained properly.Therefore,surgical correction of low astigmatism is controversial.Non-corneal ablation does not ablate corneal tissue,but the expected effect of surgery is uncertain.With the introduction of femtosecond laser technology,AK has improved the accuracy of arc-shaped incision and has gradually become an effective auxiliary means for correcting astigmatism in recent years.Therefore,this study observed the current refractive state of patients with myopia operation,including the distribution of astigmatism of varying degrees.For the moderate and high astigmatism correction,the vector analysis method was used to evaluate the correction effect of FS-LASIK and Toric ICL.For low astigmatism,the effect of low astigmatism on visual quality was discussed,and the effect of surgical correction of low astigmatism on postoperative visual quality was observed.Combined with femtosecond laser assisted AK,corneal topography guided FS-LAISK was used to correct compound myopic astigmatism,which provided a new choice for some special patients with astigmatism.A series of studies provided clinical reference for surgical correction of different degrees of astigmatism.Section ? Distribution and characteristics of refractive state in patients with myopia surgeryObjective:To observe the distribution of refractive state in patients undergoing corneal refractive surgery and summarize the distribution characteristics of myopia and astigmatismMethod:A retrospective study included 834 cases(834 eyes)of patients who underwent corneal refractive surgery from June 2016 to July 2016 at the Myopia Refractive Surgery Center of the Department of Ophthalmology,Research Institute of Field Surgery,Daping Hospital,Army Military Medical University,with an age of 20.83±3.88 years(18 to 43 years old),including 606 males(72.7%)and 228 females(27.3%).After using 0.1%Compound Tropicamide Eye Drops to paralyze the ciliary muscle,an experienced optometrist performed a retinoscopy optometry to record the best corrected visual acuity,the diopter of cylindrical power and the axial direction,which were recorded in the form of a negative cylinder and included in the study.The distribution characteristics of myopia,astigmatism and compound myopic astigmatism of patients with corneal refractive surgery were analyzed.Results:1.1 In this study,myopia degree was-4.76+1.79D,of which-4.51+1.77D for the male group and-5.41+1.68D for the female group,and the difference between the two groups was statistically significant(t=6.67,p<0.01).Low myopia,moderate myopia and high myopia accounted for 19.3%,57.8%and 22.9%,respectively.The male group was23.43%,57.92%and 18.65%,and the female group was 8.33%,57.46%and 34.21%;the difference in myopia distribution between different sex groups was statistically significant(?2=37.09,p<0.01).1.2 In this study,the astigmatism was-0.74±0.71D,of which-0.73±0.70D for the male group and-0.78±0.73D for female group,and there was no significant difference between the two groups(t=0.95,p>0.05).Astigmatism with rule,against-the-rule astigmatism and oblique astigmatism were 692 eyes(83%),27 eyes(3.2%)and 115 eyes(13.8%),respectively.The male group was 84.82%,2.14%and 13.04%,and the female group was78.07%,6.14%and 15.79%;the difference in astigmatism type distribution between different sex groups was statistically significant(?2=9.99,p<0.01).1.3 In this study,77.9%of myopic patients were combined with myopic astigmatism of different degrees.In the low myopia,moderate myopia and high myopia groups,compound myopic astigmatism was-0.58±0.57D,-0.69±0.70D and-1.00±0.77D,respectively.Compound myopic astigmatism in high myopia group was significantly higher than that in low and moderate myopia groups,and the difference was statistically significant(F=18.88,p<0.01).As the degree of myopia deepened,the proportion of myopic astigmatism below 0.5D decreased gradually and that of myopic astigmatism above 1.0D increased gradually.There was a statistically significant difference in the distribution of compound myopic astigmatism between different degrees of myopia(?2=49.78,p<0.01).Section ? Evaluation of the effects of FS-LASIK and Toric ICL on high astigmatism correction by vector analysisObjective:To compare the effects of FS-LASIK and Toric ICL on moderate and high astigmatism correctionMethod:From January 2016 to March 2017,44 eyes(44 cases)of patients with myopia surgery and preoperative myopia compound myopic astigmatism?1.0D were collected from the Department of Ophthalmology,Research Institute of Field Surgery,Daping Hospital,Army Military Medical University,including 22 eyes(22 cases)of the FS-LASIK group and 22eyes(22 cases)of the Toric ICL group.The ages of the FS-LASIK Group and the Toric ICL group were 22.72±4.85 years and 25.27±5.49 years,respectively.The subjective refraction examination of patients was performed by an experienced optometrist before surgery and 3 months after surgery,and the best corrected visual acuity,negative cylinder,axial direction and spherical equivalent were recorded.Spherical equivalent=spherical lens=1/2 cylinder.The eye with high myopic astigmatism was included in the study,and if both eyes were the same,the right eye was included in the study.Results:2.1 At 3 months after surgery,there were 6(27.27%)eyes of patients whose best corrected visual acuity were improved 1 row and above in both the FS-LASIK group and the Toric ICL group and no patients whose optimal visual acuity decreased 2 rows.2.2 At 3 months after surgery,the proportions of postoperative spherical equivalents at0D,±0.5D,±1.0D and±1.5D in the FS-LASIK group and the Toric ICL group were 18.18%and 36.36%,77.27%and 95.45%,95.45%and 95.45%,100%and 100%,respectively;postoperative astigmatism at 0D,±0.5D,±1.0D and±1.5D were 45.49%and 59.09%,86.36%and 81.82%,100%and 95.45%,100%and 100%,respectively.There was no statistically significant difference in the distribution of postoperative spherical equivalent and postoperative astigmatism between the two groups(?2=4.27,1.09;p>0.05).2.2 At 3 months after surgery,the expected correction of astigmatism,surgical correction of astigmatism,vector error,effective correction rate,error correction rate,diopter error and axial error in the FS-LASIK group and the Toric ICL group were2.00±0.50D and 1.86±0.76D,1.95±0.48D and 1.76±0.81D,0.25and 0.00,1.00 and 1.00,0.12 and 0.00,0.00 and 0.00,0.00 and 0.00(median),respectively.There was no statistically significant difference in vector analysis between the two groups.2.3 At 3 months after surgery,in astigmatism correction,the proportions of undercorrection,full correction and overcorrection in the FS-LASIK group and Toric ICL group were 36.36%and 27.27%,45.45%and 59.09%,18.18%and 13.63%,respectively.There was no statistically significant difference in the distribution between the two groups(?2=0.82,p=0.66).2.4 In the axial deviation of astigmatism correction,the clockwise and counterclockwise directions in the FS-LASIK and Toric ICL groups were 27.27%and27.27%,9.1%and 13.64%,respectively.The difference between the two groups was not statistically significant(?~2=0.24,p>0.05).However,among the patients with axial deviation of astigmatism correction,the deviation angles in the FS-LASIK group and the Toric ICL group were 4.11±3.02°and 8.11±3.82°,respectively,and the difference was statistically significant(t=-2.46,p<0.05).Section ? Effect of 0.25D astigmatism on visual qualityObjective:To observe the effect of 0.25D astigmatism on subjective and objective visual qualityMethod:Self-control study included 20 eyes(20 cases)of patients who received corneal refractive surgery at the Myopia Refractive Surgery Center of the Department of Ophthalmology,Research Institute of Field Surgery,Daping Hospital,Army Military Medical University from July 2017 to October 2017,and had the best corrected visual acuity of myopia combined with 0.25D astigmatism.After routine examination of corneal refractive surgery,in the corrected and uncorrected 0.25D astigmatism state,the contrast sensitivity test in dark environment and OQAS test were performed to record the contrast sensitivity value,OSI value,PVA value,MTFcutoff value and SR value.For patients with both eyes,the right eye was included in the study.Results:3.1 Contrast sensitivity in dark environmentThe contrast sensitivity values in the astigmatism correction group and the uncorrected group were 3c/d:1.64±0.20 and 1.65±0.18;6c/d:1.88±0.15 and 1.91±0.19;12c/d:1.58±0.24 and 1.62±0.18;18c/d:1.07±0.21 and 1.12±0.25.The values of the astigmatism correction group were slightly lower than that of the uncorrected group,but the difference was not statistically significant(t=-0.32,-0.80,-0.9,-1.28,p>0.05).3.2 In the astigmatism correction group and the uncorrected group,MTFcutoff were48.07±8.00 and 43.94±10.27,respectively,and PVA were 1.61±0.27 and 1.48±0.35,respectively,and the difference was statistically significant(t=7.22,0.23,p<0.05).OSI and SR in the two groups were 0.41±0.37 and 0.45±0.37,0.28±0.06 and 0.25±0.08,respectively.The difference was not statistically significant(t=-1.32,0.05,p>0.05).3.3 PVA100 and PVA25 in the astigmatism correction group and the uncorrected group were 1.63±0.26 and 1.48±0.34,1.29±0.26 and 1.13±0.36,respectively.The difference was statistically significant(t=2.47,3.5,p<0.05).PVA9 in the two groups was0.77±0.20 and 0.70±0.28,respectively,and the difference was not statistically significant(t=1.92,p>0.05).Section ? Effect of corneal refractive correction of 0.25D astigmatism on postoperative visual qualityObjective:To observe the effect of corneal refractive correction of 0.25D astigmatism on postoperative visual qualityMethod:In a prospective study,22 eyes(22 cases)were collected from patients with myopia correction and 0.25D preoperative myopia astigmatism at the Department of Ophthalmology,Research Institute of Field Surgery,Daping Hospital,Army Military Medical University from July 2018 to August 2018.The patients were randomly divided into astigmatism correction group and astigmatism uncorrected group by coin toss method.All patients underwent slit lamp examination,CDVA examination and optometry examination before and 1 month after surgery,and OQAS and contrast sensitivity tests were performed in dark environment.If both eyes were astigmatic equivalently,the right eye was included in the study.Results:4.1 Visual acuity and refractive stateThe visual acuity of the astigmatism correction group and the astigmatism uncorrected group were 5.05±0.07 and 5.01±0.06,respectively.The postoperative spherical lenses were0.21±0.60D and 0.18±0.49D,respectively.The postoperative cylinders were-0.25±0.21D and-0.35±0.24D,respectively.Postoperative visual acuity,spherical lens and cylinder were not statistically different between the two groups(t=0.15,0.14,1.03,p>0.05).There was no statistically significant difference between the two groups in preoperative astigmatism and postoperative astigmatism(t=-0.57,1.31,p>0.05).However,the postoperative astigmatism of the astigmatism uncorrected group was higher than that of the astigmatism correction group and its preoperative astigmatism.There was no visual loss of2 rows in either group.4.2 OQAS testPostoperative OSI,MTFcutoff,SR and PVA100,PVA20 and PVA9 in the correction group and the uncorrected group were 0.73±0.35 and 1.03±0.59,37.06±9.52 and32.14±13.78,0.19±0.04 and 0.17±0.07,1.25±0.31 and 1.06±0.46,0.9±0.26 and 0.77±0.39,0.51±1.38 and 0.46±0.24,respectively.There were no statistically significant difference between the two groups(t=1.46,0.99,1.07,1.16,0.93,0.24,p>0.05).4.3 Contrast sensitivity in dark environmentThe contrast sensitivity values of the correction group and the uncorrected group in the dark environment were 1.59±0.19 and 1.56±0.12,1.89±0.21 and 1.87±0.09,1.55±0.24 and1.54±0.29,1.22±0.21 and 1.15±0.24,respectively.The difference between the two groups was not statistically significant(t=0.54,0.32,0.12,0.69,p>0.05).Section ? Corneal topography guided FS-LAISK combined with femtosecond laser assisted AK for the correction of compound myopic astigmatismObjective:To observe the effect of corneal topography guided FS-LAISK combined with femtosecond laser assisted AK for the correction of compound myopic astigmatismMethod:A retrospective study:10 eyes(5 cases)of patients(10 cases)receiving corneal topography guided FS-LASIK surgery combined with femtosecond laser assisted AK at the Myopia Refractive Surgery Center of the Department of Ophthalmology,Research Institute of Field Surgery,Daping Hospital,Army Military Medical University from May 2016 to March 2017.All patients underwent femtosecond laser assisted AK correction of astigmatism at first,and at least 3 months later,a corneal topography guided FS-LASIK surgery was performed.The visual acuity and optometry results before the femtosecond laser assisted AK surgery and before and after the corneal topography guided FS-LASIK surgery were recorded and included in the study.Results:5.1 The spherical lens,cylinder and spherical equivalent before the femtosecond laser assisted AK and three months after the surgery were-6.13±2.15D and-6.47±2.02D,-3.55±1.39D and-1.53±0.57D,-7.90±2.26D and-7.24±2.23D,respectively.There was a slight increase in spherical lens compared with that before operation,and the cylinder and spherical equivalent were significantly reduced compared with the preoperative results;and the differences were statistically significant(t=3.10,-5.04,-2.45,p<0.05).Femtosecond laser assisted AK expected correction of astigmatism:2.95±1.14D,surgical correction astigmatism:1.68±0.38D,vector error:1.80±1.10D,effective correction rate:0.63±0.17,diopter error:1.27±0.77D,angle error:6.86±10.17°.5.2 The spherical lens,cylinder and spherical equivalent before and after the corneal topography guided FS-LASIK surgery were-6.47±2.02D and-0.23±0.49D,-1.53±0.57D and-0.40±0.41D,-7.24±2.23D and-0.34±0.57D,respectively.The spherical lens,cylinder and spherical equivalent were significantly reduced compared with the preoperative results,and the difference was statistically significant(t=-9.83,-7.65,-12.37,p<0.01).Preoperative best corrected visual acuity and postoperative uncorrected visual acuity were 4.9±0.10 and4.95±0.10.There was no statistically significant difference between the preoperative best corrected visual acuity and the postoperative uncorrected visual acuity(t=-1.15,p>0.05).5.3 Expected correction of astigmatism of corneal topography guided FS-LAISK combined with femtosecond laser assisted AK:2.95±1.14D,surgical correction of astigmatism:2.64±1.12D,vector error:0.30±0.48D,effective correction rate:0.89±0.13,error rate:0.09±0.13,diopter error:0.31±0.38D,angle error:-1.10±2.33°.Conclusions:1.Most patients with corneal refractive surgery have different degrees of compound myopic astigmatism before surgery,and the degree of compound myopic astigmatism and the proportion of high astigmatism increase with the increase of myopia degree.2.Both FS-LASIK and Toric ICL can effectively correct high astigmatism in myopia.However,when the axial deviation of astigmatism correction occurs,Toric ICL may have larger angle error.3.Correction of 0.25D astigmatism is conducive to improving visual quality and daytime visual acuity,but 0.25D astigmatism may be beneficial for improving visual quality in dark environment.4.Correction of 0.25D astigmatism has no effect on visual quality after corneal refractive surgery,which may be related to surgical factors.5.The corneal topography guided FS-LAISK combined with femtosecond laser assisted AK surgery can safely and effectively correct compound myopic astigmatism,and reduce the amount of corneal tissue ablation.However,the surgery has a longer treatment cycle and requires higher surgical design.