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The Study Of Stromal Lenticule Impantation For Treatment Of Keratoconus And Investigation In New Alternative Stromal Substitutes

Posted on:2020-06-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:W W WangFull Text:PDF
GTID:1364330578980846Subject:Clinical medicine
Abstract/Summary:PDF Full Text Request
Purpose:Keratoconus(KC)is a common non-inflammatory ectasia characterized by progressive thinning and protrusion of the cormea leading to the gradual visual impairment,irregular astigmatism,or even comeal edema and scarring.In order to explore a new idea of keratoconus treatment,the study introduced femtosecond laser assisted lens implantation before comeal crosslinking aiming at the characteristic clinical manifestation of thinning and convex of keratoconus,and explored the safety of the operation and whether it can effectively halt the progression of keratoconus.Meantime,due to the limitation of stromal lenticules used for the operation,this study further explores the application of heterogeneous corneal lenticules and bio-printed 3D corneal lenticules to enlarge the source of altermative stromal substitutes,which has profound impact on the individualized design of keratoconus surgery protocol,and provide the possibility of the further improvement of the patients9 visual acuity.Method:The retrospective analysis was conducted to analyze patients admitted from March 2016 to December 2016,including the group of patients who underwent comeal crosslinking after femtosecond laser assisted lens implantation in our hospital,and the other group of patients who received only corneal crosslinking with follow-up for at least 2 years.General data,vision and refractive status,eorneal thickness and curvature,and other ophthalmic examination results were collected and postoperative and preoperative results were compared within and between two groups to explore whether corneal crosslinking after femtosecond laser assisted lens implantation could halt the progression of keratoeonus and whether there was a differenee in the therapeutic effect with corneal crosslinking only.This study took lenticules from Bama small pigs,SD rats,and human SMILE operations as heterogeneous lenticules,and bio-printing lenticules obtained in cooperation with the School of Engineering.The four kinds of lenticules were implanted separately in the corneal stroma of New-Zealand white rabbits.The results of slit-lamp examination,anterior OCT and pathological analysis were collected to observe the biocompatibility of heterogeneous lenticules(6-month follow-up)and biological printing lenticules(1-month follow-up),to evaluate whether there were rejection reactions.Thus,to explore the feasibility of heterogeneous and bio-printing lenticules as alternative stromal substitutes.Results:Retrospective analysis of 35 eyes including the group of femtosecond laser assisted lenticules implantation before corneal crosslinking(L-CXL group)of 9 eyes,the group of coneal crosslinking with follow-up of at least 2 years(CXL group)of 26 eyes.The corneal thickness of all patients was<500 un.Three months after operation,the equivalent spherical degree increased significantly in L-CXL group and was significantly different from the CXL group.There was no significant change in the optimal correction vision in L-CXL group,but there was a significant difference between two groups.The corneal thickness,K values of the anterior surface and Kmax increased significantly after operation in L-CXL group and the significant difference was detected between two groups.There was no significant change in the K values of the posterior surface in L-CXL group.There was no significant change in the density of endothelial cells in two groups.Postoperative tests showed no significant difference in CXL group compared with preoperative parameters.The results of allogeneic corneal stromal lenticules implantation showed that the cornea was transparent without cell infiltration in the follow-up of 1,3,6 months.In the anterior section OCT,the lenticules were visible with normal position.Comeal morphology was within nornal range without obvious scarring,fibrous hyperplasia or cell infiltration.H&E staining showed there was no significant difference compared with the negative control group.The collagen fiber arrangement was normal with good fit between the implant and the recipient bed.Immunohistochemistry showed the expression of alpha-smooth muscle actin,type Ⅰ collagen and fibronectin was not significantly different from that of negative control group,except that the expression of type Ⅰ collagen in pigs was higher than that in rabbits.The results of short-term observation of 1 month after bio-printing lenticules implantation showed that the cornea was transparent with no cell infiltration observed throughout.In the anterior section OCT,the density of the implant was completely transparent as the aqueous humor without visible degradation,but mild scarring was observed at the junction area.Conclusion:Corneal crosslinking after femtosecond laser assisted lenticules implantation can effectively improve corneal thickness and prevent progression of keratoconus,but it is not superior to comeal crosslinking and will aggravate refractive errors.Heterogeneous lenticules can be applied as substitutes for corneal stroma,but bio-printing lenticules still need further observation.
Keywords/Search Tags:keratoconus, femtosecond laser assisted lenticules implantation, corneal crosslinking, corneal stromal substitute, bio-printing, 3D printing
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