Comparative Study Of The Application Of Two Cornea Astigmatism Markers In SMILE

Purpose: The purpose of this study is to explore two methods of cornea astigmatism marker in the application of femtosecond laser small incision lenticule extraction(SMILE)whether the two methods has security,effectiveness and accuracy.According to comparing and analyzing the data variation of corneal higher-order aberrations after using the two cornea astigmatism marker methods.Methods: A prospective randomized controlled study was included 94 eyes of 60 patients whose astigmatism greater or equal to 1.00 diopter(D)and underwent SMILE with between June 2018 to September 2019 in the First Affiliated Hospital of Guangxi Medical University.These patients were using two corneal astigmatism marker methods divided into Group A(used stitch indentation marker,49 eyes of 30 patients)and Group B(used straight-looking horizontal marker,45 eyes of 30 patients).In the meantime,the patients in Group A were according their diopter of cylindrical power divided into the low to moderate astigmatism(A1)(<-2.00 D 38eyes)and high astigmatism(A2)(≥-2.00 D 11eyes).The patients in Group B were according their diopter of cylindrical power divided into the low to moderate astigmatism(B1)(<-2.00D33eyes)and high astigmatism(B2)(≥-2.00 D 12eyes).Marker methods of Group A,under the slit lamp microscope and using medical marker pen to mark two points on 3 and 9 o’clock of cornea limbal,after patient lie on the operating table,then used 10/0 silk thread lightly press on 3 to 9 o’clock of cornea limbal and mark corneal epithelium,to ensure that indentation mark(this mark is too small to effect on the laser scan)could be observed by microscope.Group B marker method is as follows: make sure the patient have been sit up straight and look straight ahead,then surgeon’ sight line and the patient’s has to be on the same horizontal position,after that,use medical marker pen to mark two points on horizontal position of cornea limbal and use the Spirit Level(i Phone Rangefinders APP)to make sure this two marker points on the same level,on the same level,after patient lie on the operating table,according to those marks used medical marker pen marked on margo pupillaris and make sure these two mark on the same horizontal position.Both group’ patients all used those two methods before SMILE,using the SMILE surgical video system to take the immediate digital images of anterior segment,recording all of the surgical procedure.After the operation,analysis of the digital images and assessment of two groups’ patients cyclotorsion.Observed the data of uncorrected distance visual acuity(UCVA),corrected distance visual acuity(CDVA),postoperative cylinder,corneal higher-order aberrations and so on in Group A and Group B after their surgery 1week,1month,and 3months.Results:1.After surgery 3months,the data of all patients’ ophthalmic UDVA can reach 0.8 even better.For example,in Group A,47 eyes’(95.9%)UDVA can reach at least 1.0,and the rest of 33 eyes’(67.4%)UDVA can reach greater than1.2.In Group B,43 eyes(95.6%)of UDVA no less than 1.0,the other part of 32eyes(71.1%)of UDVA are greater than 1.2 or equal.2.Security: In Group A,after surgery 3 months with CDVA ratio of preoperative with CDVA was 1.06±0.09 and in Group B was 1.05±0.09.The result has no significant difference(P>0.05).Effectiveness: In Group A,after surgery 3months with UCVA ratio of preoperative with CDVA was 1.03±0.10,and Group B was1.01±0.10.The result has no significant difference(P>0.05).Accuracy: In group A,all patients’ diopter of cylindrical power less than or equal to-0.50 D,which 44 eyes(89.8%)less than or equal to-0.25 D after surgery3 months.In group B,all patients’ diopter of cylindrical power less than or equal to-1.00 D,which 43 eyes(95.6%)less than or equal to-0.50 D and 36 eyes(80%)less than or equal to-0.25 D after surgery 3 months.3.The cyclotorsion’ data of Group A(stitch indentation marker)were(4.07±3.17)°,Group B cyclotorsion’s data(straight-looking horizontal marker)were(5.98±4.66)°.The difference was statistically significant(P<0.05).The cyclotorsion of the low to moderate astigmatism A1 and B1 were(4.55±2.93)°and(5.89±4.46)°.The result has no significant difference(P>0.05).The data of cyclotorsion in high astigmatism A2 and B2 were(2.75±3.55)° and(6.73±5.14)°.The difference between two groups have statistically significant(P=0.046).4.All group’ of the root mean square(RMS)values of coma aberration,spherical aberration,and total HOAs statistical data were increased in varying degrees after surgery 3 months.Through this statistical of the spherical aberration,by comparison with Group B and Group A,Group B was increased.In the similar comparison,B1 was higher than A1,B2 was more increased than A2.Conclusion1.Two methods of cornea astigmatism marker in the application of SMILE has good security,feasibility and accuracy.2.Both methods could be used before SMILE surgery desalination mark,one of the method was used in Group A which is stitch indentation marker,the research shows this method is accuracy but can be tedious,according this research,patient who had a high astigmatism can be used this method.The straight-looking horizontal marker doesn’t need slit lamp,its more convenient and efficient,basis on that,patient who had he low to moderate astigmatism can be used this method.3.The spherical aberration was significantly greater in straight-looking horizontal marker than stitch indentation marker.4.After using this two cornea astigmatism marker methods,The subjective visual counterpoint is poor or the marker point is too large,then causing some errors with the cyclotorsion measurements.