Boston type I keratoprosthesis

Successful corneal solid tissue transplantation,beginning with penetrating keratoplasty(PKP),and evolving to include contemporary lamellar and endothelial keratoplasty,has been a tremendous advancement in the struggle to combat corneal blindness.However,there remain patients with high-risk features predictive of transplant failure,for whom donor keratoplasty is not a viable option.Prosthetic corneas have therefore been developed in order to meet the needs of these patients.The Boston type I keratoprosthesis(BKPro)is the most widely used prosthetic cornea in the treatment of corneal blindness.In the years since the BKPro’s introduction,refinement of surgical technique and clinical management as well as improvements in prosthetic design have contributed to promising patient outcomes,particularly in the short term.As such,patients with keratoprosthesis implants continue to grow in number,and the indications for the BKPro have commensurately increased.However,risks of permanently blinding complications after implantation persist over all stages of follow-up.For the foreseeable future,the success of keratoprosthesis(KPro)implantation will continue to depend on refined patient selection,preoperative optimization,and incisive postoperative management.Here we explore indications,surgical technique and postoperative outcomes as well as several core tenants in the management of BKPro patients:limiting glaucomatous progression,controlling inflammation,and optimizing the ocular surface.The exquisite sensitivity of the BKPro-implanted eye to perturbations in any one of these areas showcases the intimate relationship between the prosthetic device and its surrounding environment.

A novel temporary keratoprosthesis technique for vitreoretinal surgery

AIM:To investigate the safety of vitreoretinal surgery when using a soft contact lens as a temporary keratoprosthesis(TKP)in patients with severe corneal opacifications.METHODS:Three patients with simultaneous corneal and vitreoretinal pathology were treated with a soft contact lens that was used as a TKP to facilitate vitreoretinal surgery.The soft contact lens was fixated with sutures onto the globe so that no leakage was possible.RESULTS:Vitreoretinal surgery with excellent fundus view was possible in all cases.The soft contact lens allowed safe central and peripheral vitrectomy.Surgery was successful in all cases.CONCLUSION:A soft contact lens properly fixated on the globe can successfully replace a TKP.This surgical procedure has several advantages like one size fits all,low costs,and easy access to the material.

Forty-five years of keratoprosthesis study and application at the Filatov Institute: a retrospective analysis of 1060 cases

AIM: To present results of the keratoprosthesis method used at The Filatov Institute of Eye Diseases and Tissue Therapy. ·METHODS: A retrospective case series analysis was used to describe the development of new types of keratoprostheses and methods of implantation as well as different ways of leukoma strengthening. ·RESULTS: Keratoprosthesis was performed in 1 060 eyes of 1 040 patients with leukomas of different etiology: burns, 725 eyes (68.4% ); trauma, 120 eyes (11.3% ); keratitis and ocular pemphigoid, 108 eyes (10.2% ); and bullous keratopathy, 107 eyes (10.1% ). Visual acuity before keratoprosthesis consisted of light perception in 962 eyes (92% ), and 98 eyes (8% ) had minimal visual acuity (1/200-1/50). Both eyes were blind (visual acuity less than 1/200) in 955 patients (91.8% ). The period of blindness varied from 1 to 52 years. As a result of keratoprosthesis, visual acuity of ≥1/200 was restored in 1 023 of 1 060 eyes (96.5%). Visual acuity of 20/200-20/20 was achieved in 716 eyes (67.5%). At the last follow-up visit visual acuity of ≥1/200 was preserved in 806 eyes (76%), visual acuity of 20/200-20/20 was measured in 583 of 1 060 eyes (55%) and good keratoprosthesis fixation in the cornea was achieved in 986 of 1 060 eyes (93%). The minimal follow-up was 12 months (range, 12 months to 37 years, median 5 years). · CONCLUSION: Our techniques of keratoprosthesis effectively restore vision in patients with leukomas that cannot be treated by optical corneal grafting.

Experimental study on the biocompatibility of keratoprosthesis with improved titanium implant

AIM：To investigate whether hydroxyapatite（HAp）coating can improve keratoprosthesis（KPro）implant biointegration,ultimately to decrease the risk of implantassociated complications.METHODS：The modified titanium implant was designed and prepared for artificial cornea.The titanium implant was treated with sandblasting and hydroxyapatite coating by acid-base two-step method.Surface was analyzed by scanning electron microscopy（SEM）,KPro implants coated with HAp and KPro implant sandblasted were implanted in rabbits.Tissue adhesion to the implant was assessed and compared to an unmodified implant by histopathology（HE）,transmission electron microscopy（TEM）and SEM.RESULTS：SEM demonstrated successful deposition of HAp on titanium implant sandblasted（HA/SB-Ti）.The hydroxyapatite coatings caused enhancement of keratocyte proliferation compared with unmodified implant surfaces.HAp coating significantly increased adhesion forces.HAp coating of implants reduced the inflammatory response around the KPro implants in vivo.CONCLUSION：HAp-coated surfaces for use in titanium KPro implant greatly enhanced adherence of the titanium KPro implant in the rabbit cornea.

Implantation of Iakymenko keratoprosthesis in patients with severe ocular injury

AIM: To present the results of implantation of Iakymenko keratoprosthesis in five patients with vascularized corneal leukoma caused by severe ocular injury. METHODS: Iakymenko keratoprosthesis was implanted into 5 eyes of 5 patients: 4 patients were suffered from chemical burns and 1 patient from explosive injury. The preoperative visual acuity ranged from light perception to hand motion. The implantation surgery was composed of two-stage procedures. The follow-up period was from 9 months to 11 years. The outcome measures were visual acuity, retention, and complications of the keratoprosthesis. RESULTS: Vision improvements were achieved in most patients. All keratoprosthesis were retained within the follow-up period. Corneal melting occurred in one patient and fibrous closure in another patient, both of which were successfully treated. Retinal detachment occurred in one patient after surgery. CONCLUSION: Iakymenko keratoprosthesis seems to be a promising alternative for the patients with severe corneal injury, but further investigation is needed to evaluate the role of Iakymenko keratoprosthesis.

Osteo-odonto keratoprosthesis in Stevens-Johnson syndrome:a case report

·AIM:To report a successful osteo-odonto keratoprosthesis(OOKP) procedure in a case of end stage of corneal blindness due to Stevens-Johnson syndrome (SJS).·METHODS:An interventional case report.·RESULTS:We describe a 35-year-old Indian woman,a known case of SJS with bilateral dry eyes and corneal blindness (failed corneal graft with vascularised total corneal opacity in the right eye and non-healing corneal ulcer in the left eye).Vision was hand movement only in both eyes.The corneal ulcer healed with medical treatment resulting in vascularised total corneal opacity with no improvement in vision.OOKP was performed in the right eye and the vision was improved from hand movement to 6/6.The same vision was maintained in the right eye at the last follow-up 5 years after surgery.·CONCLUSION:OOKP provides good visual rehabilitation with long-term anatomically stable prosthesis in patients with end-stage of ocular surface disorders and corneal blindness secondary to SJS.·

AB088.Quality of life and visual function in patients with Boston type I keratoprosthesis

Background:To determine patient-reported vision-related quality of life(VR-QoL)following Boston type I keratoprosthesis(BI-KPro)surgery and its association with postoperative best-corrected visual acuity(BCVA).Methods:Descriptive cross-sectional study.Consecutive consenting patients with BI-KPro were included.The French National Eye Institute Visual Function Questionnaire-25 administered at 51±18 months postoperatively measured VR-QoL.Clinical charts were reviewed for demographics,indications for BI-KPro,baseline and postoperative(at time of interview)BCVA.For patients operated unilaterally,stratification of VR-QoL scores based on BCVA in the non-operated eye was performed.Multivariate linear regression was carried out,using VR-QoL scores as dependent variables,and demographics and postoperative BCVA as covariates.For patients operated bilaterally,Spearman correlation between VR-QoL scores and BCVA was performed.P<0.05 indicated statistical significance.Results:Sixty-four patients,aged 59±14 years,52%male,with a follow-up of 54±19 months,were included.Postoperative BCVA increased from baseline in all operated eyes(P=0.000).In patients with unilateral BI-KPro(n=52),the VR-QoL overall score was 70.7±25.1.Scores on all questionnaire subscales were greater when BCVA in the non-operated eye was>20/200 compared to 20/200(P=0.000).BCVA in the non-operated eye was positively associated with all subscales(P<0.01)independently of age,sex,follow-up duration and postoperative BCVA in the operated eye.In patients with bilateral BI-KPro(n=12)the VR-QoL overall score was 63.0±18.7.BCVA in the best eye positively correlated with Near/Distance activities,and social functioning subscales(P<0.05).There was no significant difference between VR-QoL scores of patients operated unilaterally vs.bilaterally.Conclusions:We describe VR-QoL more than 4 years after BI-KPro surgery.Compared to data at 1 year previously reported,our results suggest that,as vision progressively deteriorates in the operated eye,patients increasingly rely on their non-operated eye.VR-QoL after bilateral BI-KPro is assessed for the first time,and appears comparable to that after unilateral surgery.Larger,prospective,long-term studies,with assessment at baseline,are warranted.

Biomechanical evaluation of different hydroxyapatite coatings on titanium for keratoprosthesis

Stable tissue integration is important to keratoprosthesis （KPro）. The aim of this study was to evaluate the tissue bonding ability of hydroxyapatite （HAp）-coated titanium KPro. The samples were divided into three groups： test groups （IBAD group and AD group） and Ti control. The coated samples had a HAp layer created by ion beam assisted deposition （IBAD） or aerosol deposition （AD）. The surface characteristics were analyzed with SEM, AFM, and XRD. The samples were surgically inserted into the muscles of rabbits. Eight weeks after healing, the attachment to the tissue was tested with a universal test device. The three samples exhibited distinctive surface morphology. The force to remove the HAp implants from the muscles was significantly greater than that of Ti group （P〈0.01）, with the AD samples requiring the greatest force （P〈0.01）. After removal, SEM showed that the tissue was firmly attached to the surface of AD samples. Photomicrographs of the peri-implant muscles showed a layer of aligned fibrous tissue without severe inflammation. The AD samples had more fibroblasts. Results indicate that because of enhanced mechanical adhesion of soft tissue to the implants, HAp-coated Ti by AD is a suitable KPro skirt material.

Corneal transplantation outcomes after the extrusion of an intrastromal keratoprosthesis:a pilot study

This short report includes 5 eyes of 5 patients(mean age 63.2±12 years)who underwent a tectonic keratoplasty[deep anterior lamellar keratoplasty(DALK)or penetrating keratoplasty(PK)]in order to rehabilitate the eye after the extrusion of the non-perforating keratoprosthesis(Kpro)KeraKlear(KeraMed,USA).The non-perforating Kpro was extruded after a mean period of 21.4±21.8 months due to melting.In two cases,the keratoplasty was performed the same day of the non-perforating Kpro removal due to a severe melting,while in the other three cases it was performed 1 to 3 months later.Two eyes received a DALK,but in 3 eyes a macroscopic Descemetzs membrane perforation forced the conversion into a PK.The mean follow-up period after the keratoplasty was 16.8±6.6 months.No cases of rejection were recorded.All the 5 eyes achieved"anatomical success"(transparent graft,with no signs of infection or inflammation).Two eyes showed limited functional success"because the achievement of the best visual potential was prevented by the development of glaucomatous optic atrophy during the follow-up period.In conclusion,this short report presents an unexpected success of a keratoplasty performed with a tectonic purpose after the extrusion of the non-perforating Kpro because the corneal graft remained transparent,without neovascularization or scarring during the follow-up period.This initial evidence shows some encouraging results reg a rd i ng graft survival rate and the achievement of a useful visual rehabilitation with keratoplasty after a nonperforating Kpro failure in stead of repeating the Kpro implantation.

Corneal transplantation outcomes after the extrusion of an intrastromal keratoprosthesis:a pilot study

This short report includes 5 eyes of 5 patients(mean age 63.2±12 years)who underwent a tectonic keratoplasty[deep anterior lamellar keratoplasty(DALK)or penetrating keratoplasty(PK)]in order to rehabilitate the eye after the extrusion of the non-perforating keratoprosthesis(Kpro)KeraKlear(KeraMed,USA).The non-perforating Kpro was extruded after a mean period of 21.4±21.8 months due to melting.In two cases,the keratoplasty was performed the same day of the non-perforating Kpro removal due to a severe melting,while in the other three cases it was performed one to 3 months later.Two eyes received a DALK,but in 3 eyes a macroscopic Descemet membrane perforation forced the conversion into a PK.The mean follow-up period after the keratoplasty was 16.8±6.6 months.No cases of rejection were recorded.All the 5 eyes achieved“anatomical success”(transparent graft,with no signs of infection or inflammation).Two eyes showed limited“functional success”because the achievement of the best visual potential was prevented by the development of glaucomatous optic atrophy during the follow-up period.In conclusion,this short report presents an unexpected success of a keratoplasty performed with a tectonic purpose after the extrusion of the non-perforating Kpro because the corneal graft remained transparent,without neovascularization or scarring during the follow-up period.This initial evidence shows some encouraging results regarding graft survival rate and the achievement of a useful visual rehabilitation with keratoplasty after a nonperforating Kpro failure instead of repeating the Kpro implantation.

Clinical correlates of common corneal neovascular diseases: a literature review

A large subset of corneal pathologies involves the formation of new vessels(neovascularization), leading to compromised visual acuity. This article aims to review the clinical causes and presentations of corneal neovascularization(CNV) by examining the mechanisms behind common CNV-related corneal pathologies, with a particular focus on herpes simplex stromal keratitis,contact lenses-induced keratitis and CNV secondary to keratoplasty. Moreover, we reviewed CNV in the context of different types of corneal transplantation and keratoprosthesis, and summarized the most relevant treatment available so far.

Evaluation of corneal cell growth on tissue engineering materials as artificial cornea scaffolds

The keratoprosthesis(KPro;artificial cornea)is a special refractive device to replace human cornea by using heterogeneous forming materials for the implantation into the damaged eyes in order to obtain a certain vision.The main problems of artificial cornea are the biocompatibility and stability of the tissue particularly in penetrating keratoplasty.The current studies of tissue-engineered scaffold materials through comprising composites of natural and synthetic biopolymers together have developed a new way to artificial cornea.Although a wide agreement that the long-term stability of these devices would be greatly improved by the presence of cornea cells,modification of keratoprosthesis to support cornea cells remains elusive.Most of the studies on corneal substrate materials and surface modification of composites have tried to improve the growth and biocompatibility of cornea cells which can not only reduce the stimulus of heterogeneous materials,but also more importantly continuous and stable cornea cells can prevent the destruction of collagenase.The necrosis of stroma and spontaneous extrusion of the device,allow for maintenance of a precorneal tear layer,and play the role of ensuring a good optical surface and resisting bacterial infection.As a result,improvement in corneal cells has been the main aim of several recent investigations;some effort has focused on biomaterial for its well biological properties such as promoting the growth of cornea cells.The purpose of this review is to summary the growth status of the corneal cells after the implantation of several artificial corneas.

High-risk corneal allografts: A therapeutic challenge

Corneal transplantation is the most common surgical procedure amongst solid organ transplants with a high survival rate of 86% at 1-year post-grafting. This high success rate has been attributed to the immune privilege of the eye. However, mechanisms originally thought to promote immune privilege, such as the lack of antigen presenting cells and vessels in the cornea, are challenged by recent studies. Nevertheless, the immunological and physiological features of the cornea promoting a relatively weak alloimmune response is likely responsible for the high survival rate in "low-risk" settings. Furthermore, although corneal graft survival in "lowrisk" recipients is favourable, the prognosis in "high-risk" recipients for corneal graft is poor. In "high-risk" grafts, the process of indirect allorecognition is accelerated by the enhanced innate and adaptive immune responses due to pre-existing inflammation and neovascularization of the host bed. This leads to the irreversible rejection of the allograft and ultimately graft failure. Many therapeutic measures are being tested in pre-clinical and clinical studies to counter the immunological challenge of "high-risk" recipients. Despite the prevailing dogma, recent data suggest that tissue matching together with use of systemic immunosuppression may increase the likelihood of graft acceptance in "high-risk" recipients. However, immunosuppressive drugs are accompanied with intolerance/side effects and toxicity, and therefore, novel cell-based therapies are in development which target host immune cells and restore immune homeostasis without significant side effect of treatment. In addition, developments in regenerative medicinemay be able to solve both important short comings of allotransplantation:(1) graft rejection and ultimate graft failure; and(2) the lack of suitable donor corneas. The advances in technology and research indicate that wider therapeutic choices for patients may be available to address the worldwide problem of corneal blindness in both "low-risk" and "high-risk" hosts.

AB092.Database for the anatomopathological,functional and surgical characterization of the cornea

Background:The purpose of this infrastructure is to provide to the Network researchers a database and diverse related tools for the anatomical and functional analysis of the normal,pathological and surgical cornea.Methods:This database is composed of normal and pathological individuals,totaling more than 36,000 patients.It includes anatomical and functional imaging data,physiological optics data,psychometric and clinical data(medical history,surgical parameters,acuteness,etc.).Various corneal topography tools were added,giving the database a unique character:tools for analyzing individual maps,average map tools for the study and comparison of populations,3D modeling and visualization tools,statistical tools,etc.There are also screening tools for detecting various corneal conditions(LASIK,PRK,RK,keratoconus)and for secure data exchange between colleagues.Results:Several studies were made in recent years thanks to this common infrastructure.For example,this database has provided important information regarding the evolution of the 3D shape of the normal cornea with age and ametropia and has confirmed the mirror symmetry of corneas for the right and the left eyes(enantiomorphism).The different stages of Fuchs’dystrophy were also characterized to provide essential knowledge for surgery of the posterior layer of the cornea.Our database also allowed studying the anatomy of the wounds and the shape of the cornea before and after a transfixing transplant or an endothelial transplant(DSAEK and DSEK).The data on the characterization of experimentally transplanted corneas with corneal equivalents generated by tissue engineering and the recent addition of clinical data on the replacement of a diseased cornea with a synthetic corneal equivalent(keratoprosthesis)also resulted in several publications.More recently,the database has allowed to develop innovative algorithms to determine the optimal shape of an implant according to the clinical parameters of the recipient.On the other hand,we also demonstrated that the 3D shape of the cornea can be used as a biometric characteristic(such as fingerprints)for identification of individuals for various applications ranging from forensics to secure border crossings.Consequently,a new multimodal database(cornea+iris+eventually retina)was created for the purpose of biometric identifications.This database provides a unique set of anatomical and functional tools for the analysis of the cornea.It is characterized by the scientific quality and large quantity of accumulated information on the cornea and the high-level tools to exploit its content.Conclusions:The common infrastructure is easily accessible to all VHRN members on request.The database will also be accessible online in 2018(see http://cvl.concordia.ca for more information).

In vivo biological stability of chemically pretreated silicone gel inserts intended for use in keratoprostheses

Background Pretreatment with chemical agents could alter the surface chemistry of the silicone gel, which makes it suitable for epithelial migration onto its surface and thus enhances the cytobiocompatibility. This study aimed to evaluate the biological response of the corneal stroma to porous silicone gel pretreated with different chemical agents in vivo. Methods The porous silicone gels were treated with a mixed acid solution containing 23.2% H2SO4 and 0.8% K2Cr207 for 10 or 15 minutes or with 30% H202 for 15 minutes. Discs （4 mm in diameter） were inserted into interlamellar stromal pockets of New Zealand white rabbits and followed up for a period of 3 months. Clinical evaluations such as corneal infiltration, edema and neovascularization were performed daily. At 3 months, the fibroplasias and collagen deposition were examined under light and scanning electron microscopy （SEM） and by immunohistochemical analysis. Results Pretreatment of the discs obviously decreased conjunctival congestion, discharge, cornea edema, and the extent of neovascularization. More fibroblasts migrated into the pretreated discs than into the control, and collagen was deposited, indicating that the biocompatibility of the corneal replacements was enhanced by the chemical pretreatments. From immunohistochemical analysis, Type I collagen deposition in the pretreated silicone discs was greater than in the control. Conclusions Chemical treatment of silicone gel is effective in decreasing rabbit corneal inflammation, encouraging fibroblast in-growth, and enhancing tissue compatibility. Pretreated gels show good biological stability when used as a skirt material in Keratoprosthesis （Kpros）.