OBJECTIVE: To evaluate the outcome and complications after implantation of the Boston type I keratoprosthesis (Kpro) in two groups of eyes.
METHODS: We retrospectively reviewed records of 28 eyes with failed Penetrating keratoplasty (PKP) (Group A) and 31 eyes with severe ocular surface diseases who implanted Kpro. Follow-up was performed for a mean 37 months. Primary outcomes were Kpro retention and visual improvement, secondary outcomes included the occurrence of complications as endophthalmitis, retro-prosthesis membrane (RPM), intraocular pressure (IOP) abnormalities, posterior capsule opacification (PCO), graft thinning and extrusion.
RESULTS: Visual improvement was achieved in 20 eyes in Group A, and in 19 eyes in Group B. In group A, the prosthesis was retained in 25 eyes, while prosthesis retention in Group B was in 26 eyes. Group A had higher rates of PCO, high IOP, soft IOP, and graft thinning. Group B had higher risk of RPM, and endophthalmitis. Two eyes in Group A, and Five eyes in Group B required redo procedure.
CONCLUSIONS: The Boston Kpro type I is an effective procedure in eyes with high risk of keratoplasty failure and in severe ocular surface diseases, it has a high retention rate, higher in cases following failed PKP.

The Boston Keratoprosthesis type I (B-KPro) is widely used in the world, but the lack of donor corneas limits its application. This study aims to prepare the acellular porcine cornea (APC) crosslinked with ultraviolet A (UVA)/riboflavin instead of donor corneas as the scaffold for B-KPro. Decellularization of freeze-thaw combined with biological enzymes resulted in approximately 5 ng/mg DNA residue, the a-Gal removal rate of 99%, and glycosaminoglycans retention at a high level of 46.66 ± 2.59 mg/mg. UVA/ riboflavin cross-linking was adopted to induce the formation of new chemical bonds between adjacent collagen chains in the corneal stroma to improve the mechanical properties and resistance to enzymatic hydrolysis. Through comprehensive analysis of the biomechanics, enzyme degradation, immunogenicity and histological structure of the APC crosslinked at different times, CL3 (irradiation conditions, 365 nm, 3 mW/cm, 80 min, both sides) was selected and transplanted into the rabbit cornea model through interlamellar keratoplasty and penetrating keratoplasty as the scaffold of the B-KPro. Compared with the native porcine cornea (NPC) and APC, the experiment of interlamellar pocket indicated that the structure of CL3 was homogeneous without degradation and vascularization in vivo at 12 weeks after surgery. Simultaneously, the results of transplantation of B-KPro showed complete epithelialization of CL3 within 1 week, and neovascularization of the cornea indicated rejection but could be controlled with immunosuppressants. At 3 months postoperatively, the lens of B-KPro remained transparent, and the structure of CL3 was compact and uniform, accompanied by the migration and proliferation of a large number of stromal cells without degradation, suggesting the CL3 could be a promising corneal substitute.

Type I Boston keratoprosthesis is implanted in patients with severely diseased eyes who are considered poor candidates for traditional keratoplasty. Glaucoma is considered a major visual comorbidity following the implantation of type I Boston keratoprosthesis (KPro). Eyes that receive a Boston KPro are at high risk of progression of pre-existing glaucoma and the development of de novo glaucoma. Both complications can limit best-corrected visual acuity postoperatively. Diagnosis and surveillance for glaucoma in KPro eyes are fundamental to mitigate the risk of visual morbidity. However, managing these patients presents several challenges. The diagnosis of glaucoma after KPro implantation is usually hindered by inaccurate intraocular pressure (IOP) measurements and unreliable ophthalmic investigations such as visual field testing and optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL). In these eyes, medical management of glaucoma with topical medications is usually insufficient, and glaucoma surgery is usually warranted either prior to or during KPro implantation. Options for glaucoma surgery include glaucoma drainage device (GDD) and cyclodestructive procedures. The aim of this article is to highlight the incidence, pathophysiology, diagnosis, and management options of glaucoma in eyes that have undergone type I Boston keratoprosthesis.

OBJECTIVE: Vitreoretinal surgery in eyes with Boston type 1 keratoprosthesis (KPro) is challenging due to narrow optic of the KPro. This study analyzed the results of pars plana vitrectomy (PPV) using a wide-field imaging accessory, Resight®700 Fundus Viewing System (Carl Zeiss Meditec, Inc., Germany), for better intraoperative peripheral retinal imaging.
METHODS: In this retrospective case series, KPro patients who underwent simultaneous or sequential PPV at Dokuz Eylul University Hospital between June 2010 and January 2020 were evaluated in terms of anatomic and visual prognoses, as well as KPro- and PPV-associated complications.
RESULTS: Among 9 KPro eyes that necessitated vitreoretinal surgery, 3 (33.3%) underwent simultaneous KPro and PPV due to proliferative vitreoretinopaties; 6 (66.7%) underwent PPV for retinal detachment or suprachoroidal hemorrhage that appeared after KPro surgery. Retina could be attached in 7 eyes (77.8%), and vision improved in 3 eyes (33.3%). In 1 eye, injected silicone oil moved to subconjunctival area through glaucoma drainage device.
CONCLUSIONS: In eyes with a Boston KPro, wide-angle viewing systems helped handling peripheral retinal problems successfully during PPV, with no observed inadequacy of imaging. Despite anatomical success in most cases, visual prognosis depends on vitality of the macula and the optic disc.

Animal models of the Boston keratoprosthesis type 1 (KPro) are needed to study glaucoma damage after KPro implantation to control for confounding comorbidities common in human KPro recipients. The purpose of this study was to determine the feasibility of establishing a reproducible mouse model of glaucoma after KPro surgery, specifically that of a miniaturized mouse model of KPro (mKPro). In the present study, a total of 20 corneas of donor C57BL/6 mice (n = 10) were implanted in one eye of each recipient BALB/C mouse (n = 20), assembled as part of the mKPro, either with or without intraoperative lensectomy. Main feasibility outcomes consisted in incidence rates of loss of tone, capsule nicking, and lens extrusion, as well as acquisition of posterior segment optical coherence tomography (OCT) images. With lensectomy (n = 10), loss of ocular tone and retinal detachment occurred in 100% of mice. Without lensectomy (n = 10), capsule nicking and opening, as well as lens extrusion, occurred in 80% of mice. Causes of these complications included the large proportion of intraocular volume occupied by the lens, the shallow anterior chamber, and thus the lack of available intraocular volume to implant the KPro if the lens remains present. Successful mouse KPro surgery may require a great deal of practice to be useful as a reproducible model. Animal KPro models ought to be pursued further by research teams in future studies.

To evaluate titanium (Ti) sputtering of the poly(methyl methacrylate) (PMMA) stem of the Boston Keratoprosthesis (BK) as a method to enhance interfacial adhesion between the PMMA and the recipient corneal tissue.
PMMA specimens were plasma treated with Ar/O2 and coated with Ti using a DC magnetron sputtering instrument. The topography and hydrophilicity of the surfaces were characterized using atomic force microscopy and a water contact angle instrument, respectively. Scratch hardness and adhesion of the Ti film were measured using a mechanical tester. Biocompatibility assessments were performed using cultured human corneal fibroblasts and whole blood ex vivo. The optical quality of the Ti sputtered BK was evaluated using a custom-made optical bench.
By contact angle studies, the Ti coating improved PMMA hydrophilicity to match that of medical-grade Ti (Ti-6Al-4V-ELI). Ti sputtering of contact surfaces resulted in a plate-like morphology with increased surface roughness, without impacting the transparency of the BK optical component. Scratch testing indicated that the mechanical behavior of the Ti coating was similar to that of casted Ti, and the coating was stable in pull-off adhesion testing. Sputtered Ti film was highly biocompatible based on tests of cell viability, adhesion, proliferation, differentiation, collagen deposition, and keratocan expression, the properties of which exceeded those of uncoated PMMA and did not induce increased complement activation.
Titanium coating of the BK stem generated a mechanically and biologically favorable interface, which may help to enhance corneal stromal adhesion and biocompatibility.
Improving the biocompatibility of the BK PMMA stem may improve long-term outcomes of implantation.

To benchmark the optical performance of Boston Keratoprosthesis (B-KPro).
Back focal lengths (BFL) of B-KPros for various eye axial lengths were measured using an optical bench, International Organization for Standardization-certified for intraocular lens characterization, and compared against manufacturer\'s specification. The modulation transfer function (MTF) and the resolution efficiencies were measured. The theoretical geometry-dependent higher-order aberrations (HOA) were calculated. The devices were characterized with optical profilometry for estimating the surface scattering. Aberration correction and subsequent image quality improvement were simulated in CODE-V. Natural scene-imaging was performed in a mock ocular environment. Retrospective analysis of 15 B-KPro recipient eyes were presented to evaluate the possibility of achieving 20/20 best-corrected visual acuity (BCVA).
BFL measurements were in excellent agreement with the manufacturer-reported values (r = 0.999). The MTF specification exceeded what is required for achieving 20/20 visual acuity. Astigmatism and field curvature, correctable in simulations, were the primary aberrations limiting imaging performance. Profilometry of the anterior surface revealed nanoscale roughness (root-mean-square amplitude, 30-50 nm), contributing negligibly to optical scattering. Images of natural scenes obtained with a simulated B-KPro eye demonstrated good central vision, with 10/10 visual acuity (equivalent to 20/20). Full restoration of 20/20 BCVA was obtainable for over 9 years in some patients.
Theoretical and experimental considerations demonstrate that B-KPro has the optical capacity to restore 20/20 BCVA in patients. Further image quality improvement can be anticipated through correction of HOAs.
We establish an objective benchmark to characterize the optics of the B-KPro and other keratoprosthesis and propose design changes to allow improved vision in B-KPro patients.

This study aimed to describe the clinical features, surgical management of the eyelid and ocular surface, and outcomes of 16 patients implanted with a Boston type I keratoprosthesis (KPro).
A retrospective, single-center, consecutive case series of 16 patients with Stevens-Johnson syndrome (1), ocular chemical burns (12), and ocular thermal burns (3) implanted with KPro was studied. All subjects were men aged 27-51 years. Surgical treatment and outcomes for eyelid malposition, symblepharon, and glaucoma were assessed.
From September 2010 to February 2019, 29 patients were admitted to Zhongshan Ophthalmic Center for KPro implantation, of whom 16 (55%) required eyelid or ocular surface surgeries to maintain hydration and protect the corneal tissue, which is vulnerable to epithelial defects. Forty-one adnexal surgical procedures were performed. The most common indication for surgery was symblepharon, and the most frequent procedures were symblepharon lysis with ocular mucous membrane grafts and amniotic membranes (7) and full-thickness skin grafts to the eyelids (7). Preoperative conjunctival injection and corneal staining were documented in 9 (56%) and 8 (50%) eyes, respectively, and at up to 4 months postoperative follow-up (the last adnexal surgery before KPro) were recorded in 3 (19%, p = 0.03) and 2 (12%, p = 0.02) eyes, respectively. Glaucoma drainage devices were inserted in six patients. One patient with Stevens-Johnson syndrome underwent FP7 Ahmed glaucoma valve (AGV) implantation inferotemporally and developed plate exposure 2 months postoperatively. Five patients underwent FP8 AGV implantation with tube insertion into the vitreous cavity due to the scarred conjunctiva and limited subconjunctival space. In the study period, intraocular pressure (IOP) was in the normal range, and no tube or plate exposure was observed.
The ocular environment is critical for successful KPro surgery. A multidisciplinary approach for any lid and ocular surface abnormality in ocular burns or Stevens-Johnson syndrome is important to improve the quality of the ocular surface and accommodate KPro and AGV, which is vital for maintaining vision after KPro surgery. FP8 AGV may be feasible for IOP control in adult KPro cases with restricted subconjunctival space.

The use of Boston type 1 keratoprosthesis (BKPro) has significantly increased worldwide. It is no longer considered a procedure of last resort but a reasonable option for patients with otherwise poor prognosis for a traditional penetrating keratoplasty. BKPro was approved by the Food and Drug Administration in 1992 for bilateral severe corneal blindness due to multiple corneal transplant failure. Over the years, indications have extended beyond recurrent immunologic rejection to include other conditions such as chemical injury and other causes of bilateral limbal stem cell deficiency, extensive corneal neovascularization, neurotrophic corneas and hypotony, among others. Numerous advances in the design of the BKPro, improvement of preoperative, intraoperative and postoperative management have resulted in favorable outcomes and a reduction in postoperative complications. Accordingly, many studies have shown that implantation of this device is highly effective in restoring vision with very good short-term outcomes. However, due to the lifetime risk of sight-threatening complications after BKPro implantation, a longer follow-up period should provide outcomes that are more realistic. In this review, the authors examined only the results of publications with an average of at least 2 years of follow-up. The overall intermediate to long-term visual outcomes and retention rate in BKPro seem to be favorable. However, autoimmune diseases and cicatrizing conditions continue to show a higher incidence of postoperative complications that require further management.

BACKGROUND: Mooren\'s ulcer is a painful, inflammatory chronic keratitis that affects corneal periphery, progressing centripetally, ultimately ending in perforation. The first line of treatment includes systemic immunomodulators, with surgery being the last option. We present a case of bilateral Boston keratoprosthesis implantation for severe Mooren\'s ulcer that responded differently in each eye.
METHODS: A 32-year-old male with corneal opacification, anterior staphylomas, vision of hand movement, was started on systemic immunosuppression with cyclosporine. After two failed penetrating keratoplasties in each eye, high intraocular pressure despite diode cyclophotocoagulation, and cystic macular edema, we performed Boston keratoprosthesis type 1 in both eyes. The right eye responded initially well, with a best-corrected visual acuity of 20/80 and normal intraocular pressure. The left eye presented high intraocular pressure, which required cyclophotocoagulation, ultimately resulting in hypotony. Boston keratoprosthesis was performed but had peripheral corneal necrosis that progressed despite amniotic membrane transplantation and aggressive intensive treatment with medroxyprogesterone, autologous platelet-rich-in-growth-factors eye drops, and oral doxycycline. Thus, replacement of the semi-exposed Boston keratoprosthesis with tectonic penetrating keratoplasty was necessary. However, both eyes developed phthisis bulbi with final visual acuity of perception of light with poor localization.
CONCLUSIONS: Mainstay treatment of Mooren\'s ulcer is systemic immunomodulation. Surgical treatment must be considered only when risk of perforation, preferably with inflammation under control. Penetrating keratoplasty frequently fails, and Boston keratoprosthesis may be a viable option. However, postoperative complications, especially uncontrolled high intraocular pressure, corneal necrosis, and recurrence of Mooren\'s ulcer may jeopardize the outcomes and need to be addressed promptly with intensive topical and systemic treatment.