| BackgroudCorneal ectasia is a serious complication after excimer laser corneal refractive surgery,which seriously affects the visual function of patients.It is manifested as progressively steepening and thinning of the cornea,resulting in increased myopia and astigmatism.Among different treatment strategies of corneal ectasia,corneal cross-linking(CXL)is the only safe and effective method for the treatment of keratoconus and corneal ectasia,which can effectively prevent the progression of ectasia,but has limited effect on the improvement of visual function.Previous studies focused more on preventing the progression of the ectasia and neglected the improvement of postoperative visual function.With the development of corneal cross-linking technology and the improvement of patients' requirements for visual quality,many researchers are looking for new treatment methods,hoping to further improve patients' visual function while preventing the progression of the ectasia and avoiding complications.Specific corneal refractive surgery can make the corneal shape more regular and has obvious advantages in improving the postoperative visual function of patients,but it ablates part of corneal tissue and affects the biomechanical stability of cornea.Therefore,the application alone of corneal refractive surgery can not be regarded as the standard therapy for keratoconus.The combined application of CXL and corneal refractive surgery avoids the limitations of separate application.In terms of the combined application of CXL,there have been many studies on keratoconus,but few studies on corneal ectasia,and cases were mainly reported.More studies are needed to evaluate the clinical therapeutic effect.In this study,two different combined corneal cross-linking methods were used to treat corneal ectasia after LASIK,and their effects on corneal ectasia and visual quality were evaluated.ObjectiveTo observe the effects of phototherapeutic keratectomy combined with corneal cross-linking(PTK-CXL)and phototherapeutic keratectomy,photorefractive keratectomy combined with CXL(PTK-PRK-CXL)on corneal ectasia after laser in situ keratomileusis(LASIK).To evaluate the safety,effectiveness and postoperative visual quality of these two combined therapies and provide a basis for individualized options for different patients with ectasia.Methods33 patients with keratomileusis after LASIK(25 males,8 females,50 eyes)treated in Shandong Provincial Hospital Affiliated to Shandong University were enrolled.According to the different treatment methods,they were divided into two groups(PTK-CXL group and PTK-PRK-CXL group),PTK-CXL group of 19 patients(14 males,5 females,28 eyes,mean age 29.11±3.84 years)and PTK-PRK-CXL group of 14 patients(11 males,3 females,22 eyes,mean age 28.79±3.38 years).Visual acuity(UCVA,BCVA),diopter(spherical,cylinder,equivalent spherical),corneal topographic parameters(Kflat,Klsteep,Kmean,Kmax),thinnest corneal thickness(TCT),corneal endothelial cell count(ECC),high-order aberrations on the anterior surface of the cornea(total high-order aberrations on the anterior surface of the cornea,spherical aberration,coma,and trefoil aberration)were measured before treatment and 1,3,6,12 months after treatment.The change of each observation index with time was observed in two groups.The result of each observation index of the two groups was recorded at baseline and 1,3,6,12 months of follow-up respectively,and the results at different time points after surgery were compared with the results at baseline to see whether there was statistical significance.Changes in UCVA,BCVA,spherical,cylinder,Kmean,Kmax,TCT and total high-order aberration(THOA)of the anterior corneal surface in the two treatment groups were observed respectively at 6 months and 12 months after treatment and the two groups were compared to see if there was statistical significance.Before operation and 12 months after operation,the correlation between the THOA,spherical aberration(SpAb),coma,trefoil aberration of the anterior corneal surface and visual acuity(UCVA and BCVA)in the two groups was evaluated respectively.The correlation between the changes of different high-order aberrations on the anterior surface of the cornea and the changes of UCVA and BCVA in the two groups was evaluated at 12 months after surgery.Results1.Results in the two groups at 1 month,3 months,6 months and 12 months after surgery were compared to those before surgery.Both PTK-CXL and PTK-PRK-CXL combined therapies can effectively reduce the corneal curvature and improve UCVA and BCVA.This effect tended to be stable from 6 months to 12 months after surgery.(1)The difference of UCVA in PTK-PRK-CXL group at one month after surgery was not statistically significant compared with that before operation(p>0.05).At 3,6 and 12 months after surgery,the differences were statistically significant compared with that before treatment respectively,with 0.161ogMAR at 12 months of follow-up.BCVA decreased significantly at 1 month after surgery and recovered to the preoperative level at 3 months postoperatively.It was significantly improved at 6 months and 12 months after treatment,with 0.001ogMAR at 12months followup and there was statistical significance compared with that at baseline(p<0.05).Spherical refraction,cylinder and equivalent spherical refraction were significantly decreased at each time point after surgery and the differences were statistically significant(p<0.05).Kflat,Ksteep,Kmean,Kmax and TCT were significantly decreased at different time points after surgery(p<0.05).Kmax decreased from 52.89±6.08D at baseline to 46.33±4.76D at 12 months of follow-up.TCT was 425.32±31.71um at baseline and was 333.91±38.36um at 12 months postoperatively.ECC was 3005.13±262.16 cells/mm2 before surgery and decreased in different degrees at 1,3 and 6 months after surgery,with statistically significant difference(p<0.05).ECC was 2925.39±199.73cells/mm2 at 12 months followup and there was no statistical significance compared with that before operation(p>0.05).The THOA and coma of the anterior surface of the cornea were significantly reduced at 1,3,6 and 12 months of follow-up,and there were significant differences compared with those before surgery(p<0.05).The trefoil aberration increased significantly at 1 month and 3 months after operation,and the differences were statistically significant(p<0.05).There was no statistical significance at 6 and 12 months after surgery(p>0.05).The change of SpAb showed no statistical significance at any time points postoperatively.(2)UCVA and BCVA in PTK-CXL group significantly decreased at 1 month and 3 months after surgery and significantly improved at 6 and 12 months of follow-up.The differences were statistically significant compared with those before surgery(p<0.05).UCVA and BCVA at 12 months followup were 0.61ogMAR and 0.11ogMAR respectively.Spherical refraction,cylinder and equivalent spherical refraction increased significantly at 1 month after treatment and recovered to the baseline at 3 months after surgery and decreased significantly at 6,12 months postoperatively(p<0.05).Kflat increased significantly at 1 month after surgery(p<0.05)and was comparable to baseline at 3 months followup(p>0.05)and decreased significantly at 6 months and 12 months after surgery(p<0.05).Ksteep,Kmean and Kmax increased significantly at 1 month of follow-up and decreased significantly at 3,6 and 12 months after surgery(p<0.05).Kmax was 53.72±7.89D at baseline and decreased to 52.12±7.80D at 12 months after operation.TCT which was 431.82±49.75um before treatment increased significantly at 1 month postoperatively and gradually decreased at 3,6 and 12 months followup and kept stabilized beyond 6 months after treatment.TCT was 423.61±48.15um at the last follow-up.Comparing with that before surgery,the differences were statistically significant at each time point after surgery(p<0.05).ECC reduced significantly at 1 month followup and gradually increased at 3,6 and 12 months after surgery,which returned to baseline at 12 months of follow-up(p>0.05).The THOA of the anterior surface of the cornea increased slightly at 1 month after surgery(p>0.05)and gradually decreased at 3,6 and 12 months after treatment.The differences were statistically significant compared with that before operation(p<0.05).The coma increased significantly at 1 month followup and gradually decreased at 3,6 and 12 months postoperatively.Comparing with that before surgery,the differences were statistically significant at any time points after treatment(p<0.05).The trefoil aberration increased significantly at 1 month and 3 months after surgery(p<0.05)and decreased slightly at 6 months and 12 months after operation(p>0.05).The changes of SpAb were slight at 1 month and 3 months postoperatively and there were no statistical significance(p>0.05).SpAb further decreased at 6 and 12 months of follow-up and the differences were statistically significant(p<0.05).2.Changes of UCVA,BCVA,spherical,cylinder,Kmean,Kmax,TCT and THOA of the anterior corneal surface at 6 months after surgery were significantly greater in the PTK-PRK-CXL group than in the PTK-CXL group.The difference between the two treatment groups was statistically significant(p<0.05).At 12 months followup,changes of UCVA,spherical,cylinder,Kmean,Kmax,TCT and THOA were significantly greater in the PTK-PRK-CXL group than in the PTK-CXL group.The difference between the two groups was statistically significant(p<0.05).The change of BCVA was larger in PTK-PRK-CXL group than in PTK-CXL group,but the difference was not statistically significant(p>0.05).3.There was no significant correlation between THOA,SpAb,trefoil aberration of anterior corneal surface and UCVA,BCVA in the two treatment groups at baseline and 12 months of follow-up(p>0.05).In PTK-PRK-CXL group,there was no correlation between coma and UCVA before surgery and 12 months after treatment,while there was significant correlation between coma and BCVA preoperatively(p<0.05)but no correlation at 12 months postoperatively(p>0.05).In PTK-CXL group,there was no correlation between coma and UCVA before surgery and 12 months after operation(p>0.05).But there was significant correlation between coma and BCVA at baseline and 12 months of follow-up(p<0.05).At 12 months postoperatively,there was no significant correlation between the changes of THOA,coma,SpAb,trefoil aberration of the anterior corneal surface and the changes of UCVA and BCVA in the two treatment groups(p>0.05).Conclusion1.Both PTK-CXL and PTK-PRK-CXL combined therapies can effectively prevent the progression of corneal ectasia and improve the visual quality,which have no effect on corneal endothelial cells.It was proved that these two combined treatments were safe and effective in treating corneal ectasia after LASIK.2.UCVA was improved more effectively in PTK-PRK-CXL group than in PTK-CXL group.The changes of Kmean,Kmax,spherical refraction,cylinder,TCT and THOA on the anterior surface of the cornea in PTK-PRK-CXL group were significantly greater than those in the PTK-CXL group.3.After treatment of combination therapy for corneal ectasia after LASIK,the THOA,SpAb,coma,and trefoil aberration on the anterior surface of the cornea showed a downward trend.There was no significant correlation between high order aberrations and visual acuity in the two treatment groups except that there was certain correlation between the coma and BCVA.There was no significant correlation between the changes of high-order aberrations on the anterior sruface of the cornea and the changes of UCVA and BCVA in the two treatment groups(p>0.05).It showed that the change of high-order aberrations was not the key factor in improving visual acuity.4.PTK-PRK-CXL and PTK-CXL have obvious advantages for the treatment of corneal ectasia after LASIK.Different patients with corneal ectasia can choose their individualized treatment plan according to their own characteristics and requirements. |
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