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1.  Clinical results of implantation of the Chirila keratoprosthesis in rabbits 
AIMS/BACKGROUND—An ideal keratoprosthesis (KPro) would closely resemble a donor corneal button in terms of its surgical handling, optics, and capacity to heal with host tissue in order to avoid many of the complications associated with the KPros which are currently in clinical use. This study was carried out to assess the long term clinical outcomes on implantation of the core and skirt poly(2-hydroxyethyl methacrylate) KPro in animals.
METHODS—20 KPros were made and implanted as full thickness corneal replacements into rabbits and followed for up to 21 months to date.
RESULTS—80% of the prostheses have been retained, with a low incidence of complications such as cataract, glaucoma, and retroprosthetic membrane formation which are frequently associated with KPro surgery.
CONCLUSIONS—KPros of this type may offer promise in the treatment of patients for whom penetrating keratoplasty with donor material carries a poor prognosis. Refinement of the KPro and further animal trials, including implantation into abnormal corneas, are however mandatory before human implantation could be planned.

 Keywords: complications; keratoprosthesis; optics; PHEMA
PMCID: PMC1722337  PMID: 9536874
2.  Comparative experiments for in vivo fibroplasia and biological stability of four porous polymers intended for use in the Seoul-type keratoprosthesis 
Aims: To evaluate in vivo fibroplasia and biological stability of porous polymers intended for use in the Seoul-type keratoprosthesis (S-KPro).
Methods: Four porous polymers (polypropylene, two kinds of polyethylene terephthalate (PE70 and PE50), and polyurethane) were investigated. Discs of polymers were inserted into the corneal stroma of rabbits for a 2 and 5 month period. Corneal oedema and neovascularisation were evaluated. The fibroplasia and collagen deposition were examined under light and transmission electron microscopy. S-KPros, whose skirt was made of four types of polymer, were implanted into the rabbits' eyes. The retention time and complications were evaluated.
Results: Neovascularisation and corneal oedema were found in all of the disc inserted eyes, but the corneal oedema subsided within 2 months in most of the eyes. The mean number of fibroblasts increased significantly in polypropylene and PE50 disc inserted eyes compared with polyurethane disc inserted eyes. Plentiful collagen deposition was also found in both polypropylene and PE50 disc inserted eyes. Mean retention time in the polypropylene SK-Pro implanted eyes was longer than that of the other eyes (20.7 weeks). The PE70 skirt induced corneal melting around the prosthesis.
Conclusion: Polypropylene encourages fibroblast ingrowth and shows good biological stability when used as a skirt material in S-KPro.
PMCID: PMC1771209  PMID: 12084755
polypropylene; fibroplasia; Seoul-type keratoprosthesis; porous polymers
3.  Novel materials to enhance keratoprosthesis integration 
BACKGROUND—The successful integration of keratoprostheses (KPros) within the cornea depends in part on peripheral host keratocyte adhesion to anchor the implant in place and prevent epithelial downgrowth. The following study incorporated different acrylate co-monomers with poly(hydroxyethyl methacrylate) (p(HEMA)) and measured the suitability of these materials as potential skirt materials in terms of their ability to enhance keratocyte adhesion to p(HEMA).
METHODS—p(HEMA) hydrogels incorporating varying amounts of the acrylate co-monomers methacrylic acid (MA), 2-(dimethylamino)ethyl methacrylate (DEM), or phenoxyethyl methacrylate (PEM) were formed by free radical polymerisation. Keratocytes were seeded onto discs of each material and incubated at 37°C for 72 hours. Assays for viable cell adhesion were carried out. A viability/cytotoxicity assay using solutions of calcein-AM (0.5 mM) and ethidium homodimer-1 (EthD-1) (0.5 µM) were used to measure viable and non-viable cell adhesion, respectively. An ATP assay was also used to quantify cell adhesion in terms of the amount of ATP present following lysis of adherent cells.
RESULTS—The viability/cytotoxicity assays indicated that the incorporation of 15 mol% of the co-monomer PEM or of 20 mol% DEM increased cell adhesion to p(HEMA) by at least four times. The ATP assays confirmed the results for PEM but absorption of ATP to the DEM containing hydrogel indicated that the assay was not a suitable measure of cell adhesion to this material.
CONCLUSIONS—The properties of p(HEMA) may be moderated to enhance keratocyte adhesion by the incorporation of PEM or DEM suggesting that these may be suitable materials for use in the further development of a novel KPro skirt material.

PMCID: PMC1723503  PMID: 10837393
4.  Osteo-odonto keratoprosthesis in Stevens-Johnson syndrome: a case report 
To report a successful osteo-odonto keratoprosthesis (OOKP) procedure in a case of end stage of corneal blindness due to Stevens-Johnson syndrome (SJS).
An interventional case report.
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.
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.
PMCID: PMC3340699  PMID: 22553646
osteo-odonto keratoprosthesis; Stevens-Johnson syndrome; corneal blindness
5.  Legeais BioKpro III keratoprosthesis implantation: long term results in seven patients 
The British Journal of Ophthalmology  2006;90(9):1146-1151.
The long term results of the Legeais BioKpro III keratoprosthesis are presented for seven patients with severe corneal scarring.
The study took place at Moorfields Eye Hospital, London. Patients had either end stage ocular surface disease or corneal opacification after multiple failed graft surgery, with the potential for significant visual improvement. After insertion the device was covered with a conjunctival flap or buccal mucous membrane graft, which was later opened to expose the optic. The outcome measures were vision, complications, and retention of the device.
The BioKpro III was inserted into seven patients with severe corneal scarring: ocular cicatricial pemphigoid, measles keratitis, thermal injury, Stevens‐Johnson syndrome, aniridia, chemical injury, and congenital rubella. The follow up was 18–48 months. The keratoprosthesis failed in six, because of extrusion occurring 2–28 months postoperatively. Retroprosthetic membranes occurred in three patients, and endophthalmitis in one. Vision improved from hand movements to 6/12 in the only patient who retained the KPro; however he was troubled by mucus accumulation on the optic.
The one success has been in a patient with thermal burns. The remaining results have been poor, with the KPro extruding in six of the seven patients.
PMCID: PMC1857381  PMID: 16929061
keratoprosthesis; corneal blindness
6.  Glaucoma Associated with Boston Type 1 Keratoprosthesis 
Cornea  2012;31(2):134-139.
To evaluate outcomes of the Boston Type 1 keratoprosthesis (KPro) and associated incidence of glaucoma.
Retrospective cohort study.
All patients who underwent KPro surgery at one institution from 2003-2009 with at least 3 months follow-up.
Preoperative visual acuity, diagnosis, history of glaucoma, intraoperative and postoperative parameters were recorded. Statistical analysis was performed to identify factors that may influence increase in intraocular pressure (IOP) and glaucoma development or progression after surgery.
Main Outcome Measures
Best corrected visual acuity (BCVA), IOP, postoperative medical and surgical treatments for glaucoma, and KPro retention and complications.
Thirty-six KPro procedures were performed in 30 eyes of 29 patients with mean (± SD) follow-up of 17±19 months (range 3-67 months). The main indication for KPro implantation was corneal graft failure (77%). Primary KPros were performed in 23% of eyes for limbal stem cell deficiency secondary to chemical burns and aniridia, and for herpetic disease. Median preoperative BCVA was hand motions with an overall improvement to 20/330 (range 20/20 to hand motions) at nine months postoperatively; mean BCVA was 20/600 (range 20/40 to NLP) at last follow-up. Twenty eyes (67%) had a preoperative history of glaucoma with eight of those eyes (40%) having undergone prior glaucoma surgery. Twenty-one eyes (70%) underwent concomitant glaucoma surgery. Postoperative increased IOP (22 mmHg or higher) was noted in 15 eyes (50%) while definite glaucoma development or progression was noted in 7 of those 15 eyes (23% of total eyes). Mean BCVA at last follow-up in eyes with glaucoma development or progression was 3/200 compared to 20/563 in the remaining 23 eyes. Six patients (20%) required repeat KPro implantation, and retroprosthetic membranes developed in 23 eyes (77%). No patient developed vitritis or infectious endophthalmitis.
The Boston Type 1 KPro is an effective option for management of eyes with poor prognosis for primary or repeat penetrating keratoplasty. Visual potential is limited by preoperative comorbidities; however, glaucoma development or progression of pre-existing glaucoma is a significant cause of postoperative visual loss. Rigorous perioperative management of elevated IOP is essential for long-term success of KPro surgery.
PMCID: PMC3539166  PMID: 22134402
Boston Type 1 Keratoprosthesis; Glaucoma; Keratoplasty
7.  Hydroxyapatite for Keratoprosthesis Biointegration 
Biointegration, one of the important problems facing keratoprostheses, was addressed by coating a model material with hydroxyapatite. The coating enhanced cell viability in vitro and biointegration ex vivo and reduced inflammation in vivo.
Integration of keratoprosthesis with the surrounding cornea is very important in preventing bacterial invasion, which may cause ocular injury. Here the authors investigated whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) biointegration, using polymethyl methacrylate (PMMA)—the principal component of the Boston KPro—as a model polymer.
HAp coatings were induced on PMMA discs after treatment with concentrated NaOH and coating with poly-dopamine (PDA) or polydopamine and then with 11-mercaptoundecanoic acid (11-MUA). Coatings were characterized chemically (Fourier transform infrared spectroscopy [FTIR], energy dispersive X-ray spectroscopy [EDX]) and morphologically (SEM) and were used as substrates for keratocyte growth in vitro. Cylinders of coated PMMA were implanted in porcine corneas ex vivo for 2 weeks, and the force required to pull them out was measured. The inflammatory reaction to coated discs was assessed in the rabbit cornea in vivo.
FTIR of the coatings showed absorption bands characteristic of phosphate groups, and EDX showed that the Ca/P ratios were close to those of HAp. By SEM, each method resulted in morphologically distinct HAp films; the 11-MUA group had the most uniform coating. The hydroxyapatite coatings caused comparable enhancement of keratocyte proliferation compared with unmodified PMMA surfaces. HAp coating significantly increased the force and work required to pull PMMA cylinders out of porcine corneas ex vivo. HAp coating of implants reduced the inflammatory response around the PMMA implants in vivo.
These results are encouraging for the potential of HAp-coated surfaces for use in keratoprostheses.
PMCID: PMC3183975  PMID: 21849419
8.  Five year follow up of biocolonisable microporous fluorocarbon haptic (BIOKOP) keratoprosthesis implantation in patients with high risk of corneal graft failure 
The British Journal of Ophthalmology  2004;88(12):1585-1589.
Aim: To study the anatomical and visual performance following implantation of a model of artificial cornea and to evaluate the postoperative long term complications.
Methods: 11 eyes of 11 patients with bilateral corneal blindness considered as potentially having high risk of failure of penetrating corneal keratoplasty were implanted with biocolonisable Kpro keratoprosthesis (BIOKOP I, FCI, Rantigny, France) in the period between January 1996 and May 1998. Only one eye was implanted in all patients and followed up for a period of 60 months. The visual outcome, anatomical and functional stability, complications, and the general performance of the keratoprosthesis were evaluated.
Results: The keratoprosthesis (BIOKOP I) only 36.3% remained in position to date. In the patients’ last visit five eyes (45.4%) were blind and one (9.0%) showed a slight improvement in the best corrected visual acuity (BCVA) in comparison to preoperative tests. Six eyes (54.5%) showed improved BCVA before having postoperative complications. Four eyes underwent replacement of a BIOKOP I Kpro with a BIOKOP II as a result of extrusion. The keratoprostheses remained anatomically in situ for a mean of 25.5 months and their functional performance period was limited to a mean of 22 months.
Conclusion: Corneal keratoprosthesis (BIOKOP I, II) does not provide a stable anatomical relation with the surrounding ocular structures. Its ability to restore vision is limited to a short postoperative period in eyes implanted with severe ocular surface disease.
PMCID: PMC1772453  PMID: 15550368
corneal graft failure; penetrating keratoplasty; keratoprosthesis
9.  Hydroxyapatite promotes superior keratocyte adhesion and proliferation in comparison with current keratoprosthesis skirt materials 
The British Journal of Ophthalmology  2005;89(10):1356-1362.
Aim: Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors’ aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses.
Methods: Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy.
Results: Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). ß1 integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent.
Conclusions: Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates.
PMCID: PMC1772890  PMID: 16170132
keratoprosthesis; osteoodontokeratoprosthesis; hydroxyapatite; polytetrafluoroethylene; PHEMA
10.  Sessile macrophages forming clear endothelium-like membrane on inside of successful keratoprosthesis. 
Clinical observation and cytological study of a reasonably successful keratoprosthesis removed along with a corneal button about 20 years after its implantation in an aphakic eye revealed an acellular epithelium-like film on its outer surface, firm anchoring of its supporting skirt by stable fibrous connections to the corneal stroma, and a continuous separating membrane composed of a homogeneous proteinaceous film and fibroblast-like cells of macrophage origin on its inner surface. The significance of the successful adaptation of the plastic materials of the prosthesis to the tissues of the cornea and the fluids of the inner eye for the future of tissue engineering in the region of the eye is discussed.
PMCID: PMC1298663  PMID: 6398933
11.  High-Resolution Spectral Domain Anterior Segment Optical Coherence Tomography in Type 1 Boston Keratoprosthesis 
Cornea  2013;32(7):951-955.
To report the results of imaging using high-resolution, Fourier domain anterior segment optical coherence tomography (AS-OCT) to evaluate patients with a type 1 Boston Keratoprosthesis (KPro).
We performed a retrospective comparative study of patients in whom we implanted the Boston KPro. A total of 26 eyes of 23 patients from the Cornea Service at the University of California Davis Eye Center were included. Subjects were evaluated with the Spectralis AS-OCT (Heidelberg Engineering GmbH).
Preoperative diagnoses for KPro surgery included failed corneal transplant (69%), chemical burn (23%), and aniridia (8%). The average age of patients was 63.2 years (range, 17–88 years). Fifty-four percent of the patients were female. The mean duration between the KPro surgery and the acquisition of high-resolution AS-OCT imaging was 35.8 months (range, 2–90 months). The most commonly observed finding was retroprosthetic membrane formation, which we found in 77% of KPro eyes. In 65% of KPro eyes, we identified epithelium behind the front plate, and in 54%, we identified an epithelial lip over the anterior surface of the KPro front plate. In 31% of KPro eyes, we identified periprosthetic cysts, gaps or spaces, and thinning in the corneal carrier graft.
Fourier domain AS-OCT is a useful noninvasive imaging technique in patients with a KPro and provides the ability to identify changes that are sometimes difficult to appreciate by clinical evaluation. The higher resolution Fourier domain systems may aid in the clinical diagnosis and management of pathology that might not be imaged with instruments of lower resolution. AS-OCT has the potential for monitoring the anatomic stability of an implanted KPro and may also help to monitor for complications. Moreover, high-resolution imaging may enhance our understanding of periprosthetic anatomy.
PMCID: PMC3741091  PMID: 23591146
Boston type 1 Keratoprosthesis; anterior segment optical coherence tomography; Spectralis; spectral domain; Fourier domain; KPro; OCT
12.  The Boston Keratoprosthesis: Comparing Corneal Epithelial Cell Compatibility with Titanium and PMMA 
Cornea  2009;28(7):808-811.
To determine in vitro whether titanium is superior in corneal cell compatibility to standard polymethyl-methacrylate (PMMA) for the Boston Keratoprosthesis (KPro).
Human corneal-limbal epithelial (HCLE) cells were cultured 24, 48, 72, 96, 120, 144, or 168 hours in culture plates alone (controls) or with PMMA or titanium discs. Experiments were performed in triplicate and repeated (final n = 6). To determine if a soluble, toxic factor is emitted from materials, concurrent experiments at 48 and 144 hours were performed with discs placed in Transwell Supports, with HCLE cells plated beneath. As an additional test for soluble factors, cells were incubated 24 hours with disc-conditioned media, and number of viable cells per well was quantified at each timepoint by proliferation assay. To determine if delayed cell proliferation was attributable to cell death, HCLE cell death was measured under all conditions and quantified at each timepoint by cytotoxicity assay. The effects of material on HCLE cell proliferation over time was determined by repeated measures ANOVA. P < 0.05 was statistically significant.
HCLE cell proliferation was greater in wells with titanium discs compared to PMMA. Differences between the test discs and control non-disc cocultures were statistically significant over time for both cell proliferation (P = 0.001) and death (P = 0.0025). No significant difference was found using Transwells (P = 0.9836) or disc-conditioned media (P = 0.36).
This in vitro HCLE cell model demonstrates significantly increased cell proliferation and decreased cell death with cell/titanium contact compared to cell/PMMA contact. Moreover, differences are unlikely attributable to a soluble factor. Prospective in vivo analysis of the two KPro biomaterials is indicated.
PMCID: PMC4263318  PMID: 19574903
Boston Keratoprosthesis; biomaterials; titanium; corneal cell compatibility
13.  Short-Term Visual Outcomes of Boston Keratoprosthesis Type I in Saudi Arabia 
To evaluate the visual outcomes, complications and retention of threadless type I Boston keratoprosthesis (KPro) in Saudi Arabia.
Materials and Methods:
Retrospective analysis of four eyes of four patients (one female and three males; age range: 48 to 72 years) who underwent Boston type I threadless KPro implantation between January and December 2009.
In the median follow-up of 11 months (range 6 to 14 months), visual outcomes were satisfactory. Preoperative diagnosis included two patients of post-trachoma dense vascularized corneal scarring, one patient of corneal alkali burn and one patient of repeated failed corneal grafts. All patients demonstrated significant improvement in vision; with pre-operative visual acuity of hand movements (HM), counting fingers and HM improved to best corrected visual acuity (BCVA) of 20/200, 20/60, 20/50 and 20/30 on their last follow-up visits respectively. None of the patients developed glaucoma as a result of the procedure. No retro-prosthetic membrane developed till the last follow-up visit. One of the four patients had a corneal melt (due to severe dryness associated with trachoma) 6 months after the KPro implantation and underwent a successful KPro revision. Despite the relatively poor prognosis expected in alkali burn eye, the patient attained the maximum BCVA (20/30) of the four eye series on the last follow-up visit at six months.
In consistent with the earlier reports from other parts of the world, all the 4 eyes had a significant increase in vision after Boston type I KPro implantation. However, patients require close lifelong follow-up to manage any complications.
PMCID: PMC3277030  PMID: 22346120
Alkali Burn; Boston Keratoprosthesis; Trachoma
14.  Strampelli's osteo-odonto-keratoprosthesis. Clinical and histological long-term features of three prostheses. 
The histological features are reported of osteo-odonto-acrylic laminae removed from three patients who for differing underlying causes received Strampelli's osteo-odonto-keratoprostheses (OOK) 20, 16, and 12 years previously. It appears that preservation of the alveolar-dental ligament plays a definitive role in the maintenance of the prosthesis. If this tissue undergoes necrosis as a consequence of an inflammatory disease the implanted material is eventually lost. However when no such event occurs the OOK is well preserved and well tolerated even 20 years after implantation.
PMCID: PMC504235  PMID: 1390492
15.  In vivo comparison of three different porous materials intended for use in a keratoprosthesis 
AIM—The goal was to compare the biological response of the corneal stroma with three porous materials: a melt blown microfibre web of polybutylene:polypropylene (80:20); a polyester spun laced fabric (polyethylene terephthalate), and an expanded polytetrafluoroethylene. Fifty per cent of each of the materials were modified using argon radio frequency.
METHODS—Discs (6 mm in diameter) were inserted into interlamellar stromal pockets and followed for a period of 12 weeks. Clinical evaluations were performed weekly. At 6 and 12 weeks, fibroplasia and the distribution of matrix proteins and growth factors (bFGF and TGF-β) were evaluated immunohistochemically. The characterisation of glycosaminoglycans was determined after selective extraction and digestion.
RESULTS—The response to the disc resembled that of a wound with a decrease in keratan sulphate and an increase in dermatan sulphate. Pretreatment of the discs reduced corneal oedema and neovascularisation. Heparan sulphate, not normally detected in the corneal stroma, was detected in the region immediately surrounding the disc and in the discs of some materials. The presence of glycosaminoglycans and collagens in the disc indicated that cells had migrated into the disc and deposited a complex matrix in all three materials. The collagen response was not surface specific. bFGF and TGF-β were detected in the region between the disc and the stroma in the polybutylene material and became diffuse with time.
CONCLUSION—Fibroplasia occurred most rapidly into the polyester discs but was accompanied by a large number of inflammatory cells. While the distribution of collagens was not altered by the material, the expression and distribution of growth factors was material dependent. bFGF was expressed transiently and occurred before that of TGF-β. It is predicted that the transient expression of growth factors mediates the regulation of matrix proteins.

 Keywords: synthetic cornea; basic fibroblast growth factor; glycosaminoglycans; wound healing; cornea
PMCID: PMC1722587  PMID: 9713067
16.  Biocompatibility and biofilm inhibition of N,N-hexyl,methyl-polyethylenimine bonded to Boston Keratoprosthesis materials 
Biomaterials  2011;32(34):8783-8796.
The biocompatibility and antibacterial properties of N,N-hexyl,methyl-polyethylenimine (HMPEI) covalently attached to the Boston Keratoprosthesis (B-KPro) materials was evaluated. By means of confocal and electron microscopies, we observed that HMPEI-derivatized materials exert an inhibitory effect on biofilm formation by Staphylococcus aureus clinical isolates, as compared to the parent poly(methyl methacrylate) (PMMA) and titanium. There was no additional corneal epithelial cell cytotoxicity of HMPEI-coated PMMA compared to that of control PMMA in tissue cultures in vitro. Likewise, no toxicity or adverse reactivity was detected with HMPEI-derivatized PMMA or titanium compared to those of the control materials after intrastromal or anterior chamber implantation in rabbits in vivo.
PMCID: PMC3410931  PMID: 21903257
antibacterial; polyethylenimine (PEI); keratoprosthesis; PMMA; titanium; Staphylococcus aureus; corneal cytotoxicity
17.  Outcomes of the Boston Keratoprosthesis in Jordan 
To report the indications, outcomes, and complications of the Boston type I keratoprosthesis (KPro) from the first Jordanian study on the subject.
Materials and Methods:
A retrospective chart review was conducted on 20 eyes of 19 consecutive patients who had Boston type I KPro implantation at King Abdullah University Hospital. Surgeries were performed by the same surgeon (WS) from November 2007 to March 2010. Data collected included age, sex, primary indication, number of previous grafts, preoperative comorbidities, visual acuity before and after surgery, and complications.
The mean age of the participants was 51.7±19.9 years (range: 10–80 years). The mean follow-up was 18.1±9.5 months (range: 3–6 months). The most common primary corneal pathology was vascularized corneal opacity (40%). Best corrected visual acuity (BCVA) improved significantly in 85% of eyes; 65% had a BCVA of 20/200 or better and 25% had a BCVA of 20/50 or better. The most frequent complication was retroprosthesis membrane (RPM) formation, which occurred in 45% of eyes. Two eyes (10%) had implant extrusion and required further surgery.
Boston Kpro offers a reasonably safe and effective solution for patients with corneal blindness in whom the prognosis for natural corneal grafting is poor.
PMCID: PMC3277032  PMID: 22346122
Graft Rejection; Keratoprosthesis; Visual Acuity; Complications
18.  A Novel Murine Model for Keratoprosthesis 
To establish a murine model for keratoprosthesis.
A miniature keratoprosthesis (m-KPro) device was created consisting of a poly[methyl methacrylate] front part and a titanium back plate, designed after the Boston KPro, which is in widespread clinical use. BALB/c mice were used and a 2 mm in diameter donor cornea was punched out. After 2-mm trepanation of the syngeneic recipient cornea, extracapsular crystalline lens extraction was performed. The m-KPro was assembled onto the cornea button in a similar manner to human KPro implantation. The cornea–device complex was secured to the recipient bed with eight interrupted 11-0 sutures. All mice (n = 10) were followed up for 8 weeks postoperatively.
All m-KPros were successfully implanted and retained in all 10 animals. There were no critical complications such as endophthalmitis, corneal melting, device extrusions, leakage, extensive inflammation, or weight loss in the animals. We observed mild to moderate donor and host corneal neovascularization in all cases throughout the follow-up period.
We have established a novel murine model of KPro implantation that we anticipate will serve as a good experimental system for evaluating host responses after KPro surgery.
We have established a novel murine model of KPro implantation that we anticipate will serve as a good experimental system for evaluating host responses after KPro surgery.
PMCID: PMC4059078  PMID: 24833747
keratoprosthesis; murine model
19.  Pars plana vitrectomy through the Boston Keratoprosthesis type 1 
Eye  2013;27(6):767-769.
To ascertain the feasibility of pars plana vitrectomy (PPV) through a permanent Boston Keratoprosthesis type 1 (KPro) without the use of a temporary KPro.
A retrospective interventional case series. Eyes implanted with Boston KPro type 1 between 2008 and 2011 requiring PPV for vitreoretinal complications were included. Feasibility of PPV through the KPro, its anatomical and functional success were studied.
Five out of 70 patients required PPV for vitreoretinal complications post-KPro surgery resulting in an incidence of 7%. PPV was feasible through the Boston KPro with no deleterious effects on the corneal carrier or the KPro itself. Repeat PPV was necessary in some cases. Although anatomical repair of the vitreoretinal complications was achieved in most cases, post PPV visual acuity remained poor in the majority.
Our study suggests that although PPV through the Boston KPro is a viable approach for vitreoretinal disease repair, visual rehabilitation remains poor.
PMCID: PMC3682363  PMID: 23579405
pars plana vitrectomy; boston keratoprosthesis type 1; KPro outcomes; vitreoretinal complications; artificial corneal transplants
20.  Cost effectiveness of the type II Boston keratoprosthesis 
Eye  2010;25(3):342-349.
Despite demonstrated cost effectiveness, not all corneal disorders are amenable to type I Boston keratoprosthesis (KPro) implantation. This includes patients with autoimmune diseases, such as Stevens–Johnson syndrome/toxic epidermal necrolysis. Type II KPro is implanted through the eyelids in severe dry eye and cicatricial diseases, and its cost effectiveness was sought.
Patients and methods
In a retrospective chart review, 29 patients who underwent type II KPro surgery at the Massachusetts Eye and Ear Infirmary between the years 2000 and 2009 were identified. A total of 11 patients had 5-year follow-up data. Average cost effectiveness was determined by cost-utility analysis, comparing type II KPro surgery with no further intervention.
Using the current parameters, the cost utility of KPro from third-party insurer (Medicare) perspective was 63 196 $/quality-adjusted life year.
Efforts to refer those less likely to benefit from traditional corneal transplantation or type I KPro, for type II KPro surgery, may decrease both patient and societal costs.
PMCID: PMC3178310  PMID: 21183944
decision analysis; cost utility; cost effectiveness; keratoprosthesis; autoimmune diseases
21.  Microkeratome assisted deep lamellar keratoprosthesis 
To establish a keratoprosthesis (Kpro) surgical technique that maintains an intact superficial corneal layer.
A manual microkeratome (Moria LSK‐1) was used to create a 130 μm flap of approximately 10 mm diameter in the right eye of Japanese white rabbits. The stoma beneath the flap area was dissected before the removal of a 5.0 mm stromal disc. A 5.0 mm collagen I immobilised poly(vinyl alcohol) (COL‐PVA) disc was placed on the exposed posterior stroma close to Descemet's membrane. The flap was repositioned and fixed using 10‐0 nylon sutures, which were removed 2 days following surgery. The corneas were followed clinically by slit lamp microscopy and photographs. Rabbits were sacrificed after 6 months, and the transplanted corneas were examined histologically by haematoxylin and eosin staining and immunohistochemistry against vimentin and α‐smooth muscle actin (α‐SMA).
The transplanted COL‐PVA discs remained transparent throughout the study, with no complications related to the flap or overlying epithelium. The interface between COL‐PVA and Descemet's membrane remained clear without signs of opacification caused by scarring or cellular deposition. Pathology revealed the intact COL‐PVA polymer in the posterior stroma, with minimal cellular infiltration along the anterior and posterior interfaces. Immunohistology shows vimentin and α‐SMA staining at levels comparable to lamellar keratoplasty control.
Microkeratome assisted deep lamellar keratoprosthesis may be a safe technique for the transplantation of artificial hydrogels for therapeutic purposes.
PMCID: PMC1857140  PMID: 16597665
keratoprosthesis; transplantation; microkeratome; rabbit
22.  Optical Functional Properties of the Boston Keratoprosthesis 
To evaluate the optical characteristics of the Boston Keratoprosthesis (KPro), identify glare sources, evaluate possible glare control, and examine the benefit of implanting when the fellow eye has normal vision.
Computed and optical-bench-measured point spread function (PSF) and glare sources were compared. A translucent plastic cornea was used to determine the impact of glare due to scatter in the cornea, and its control with a dark-iris tinted contact lens. The effect of glare in implanted eyes was measured with a Mentor Brightness Acuity Test (BAT), with and without the dark-iris contact lens. The computed and measured visual fields were compared. Stereopsis was measured in patients with an intact fellow eye.
The computed and measured MTFs for the KPro were found to be very close to the diffraction limit. Both the model-eye measurements and patients' BAT glare responses identified that the hazy corneal graft surrounding the KPro is the main source of glare, and can be controlled with a dark-iris contact lens. The lid effectively blocks the light that would be scattered in the hazy cornea of patients implanted with the Type II KPro. An intact fellow eye remains the dominant eye, with better acuity, and the KPro eye supports only minimal stereo ability and does not expand the binocular visual field.
Glare can be reduced significantly with the use of a contact lens with a dark iris. Implanting the KPro in a patient whose fellow eye has normal or near normal vision does not seem to improve visual function.
PMCID: PMC2808421  PMID: 19815733
Keratoprosthesis; Optics; Psychophysics; Glare; Stereopsis; Visual fields
23.  Optical Functional Properties of the Boston Keratoprosthesis 
Disability glare with keratoprosthesis can be reduced by preserving the natural iris as much as practical, or it can be significantly reduced with the use of a soft bandage contact lens with a dark iris tint. Implanting the keratoprosthesis in a patient in whom the fellow eye has normal or near normal vision does not seem to improve visual function.
To evaluate the optical characteristics of the Boston Keratoprosthesis (KPro), identify glare sources, evaluate possible glare control, and examine the benefit of implantation when the fellow eye has normal vision.
Computed and optical-bench-measured point spread function (PSF) and glare sources were compared. A translucent plastic cornea was used to determine the impact of glare caused by scatter in the cornea and its control with a dark-iris tinted contact lens. The effect of glare in implanted eyes was measured with a brightness acuity test (BAT), with and without the dark-iris contact lens. Computed and measured visual fields were compared. Stereopsis was measured in patients with an intact fellow eye.
Computed and measured modulation transfer functions for the KPro were found to be very close to the diffraction limit. Both the model-eye measurements and patients' BAT glare responses identified that the hazy corneal graft surrounding the KPro is the main source of glare and can be controlled with a dark-iris contact lens. The lid effectively blocks the light that would be scattered in the hazy cornea of patients in whom the type II KPro was implanted. An intact fellow eye remains the dominant eye, with better acuity, and the KPro eye supports only minimal stereo ability and does not expand the binocular visual field.
Glare can be reduced significantly with the use of a contact lens with a dark iris. Implanting the KPro in a patient whose fellow eye has normal or near normal vision does not seem to improve visual function.
PMCID: PMC2808421  PMID: 19815733
24.  Use of a Porous Polyethylene Lid Spacer for Management of Eyelid Retraction in Patients with Boston Type II Keratoprosthesis 
Orbit (Amsterdam, Netherlands)  2013;32(4):247-249.
To report a novel application of a porous polyethylene implant for lid stabilization and management of eyelid retraction in a patient with an exposed Boston Keratoprosthesis Type II.
A 54-year-old woman with a history of mucous membrane pemphigoid and failed penetrating keratoplasty of the left eye underwent implantation of a Boston Keratoprosthesis (KPro) Type II along with permanent surgical fusion of the upper and lower lids of the left eye in January 2010. At one month follow-up, significant retraction of the lower lid around the inferior margin of the optic was noted, resulting in partial exposure of the keratoprosthesis. The patient subsequently underwent left lower eyelid reconstruction with a porous polyethylene implant to ensure coverage and stability of the KPro.
Eyelid reconstruction using a porous polyethylene implant resulted in stable retention of the KPro Type II for over 2 years.
In patients with Boston KPro Type II in the setting of severe cicatrizing ocular surface disease, the use of a porous polyethylene implant during eyelid reconstruction around the KPro optic may aid in maintaining eyelid integrity and improving KPro stability and longevity.
PMCID: PMC4111420  PMID: 23663113
Boston keratoprosthesis; Medpor; porous polyetheylene
25.  Low-Cost and Readily Available Tissue Carriers for the Boston Keratoprosthesis: A Review of Possibilities 
Journal of Ophthalmology  2013;2013:686587.
The Boston keratoprosthesis (B-KPro), currently the most commonly used artificial cornea worldwide, can provide rapid visual rehabilitation for eyes with severe corneal opacities not suitable for standard corneal transplantation. However, the B-KPro presently needs a corneal graft as a tissue carrier. Although corneal allograft tissue is readily available in the United States and other developed countries with established eye banks, the worldwide need vastly exceeds supply. Therefore, a simple, safe, and inexpensive alternative to corneal allografts is desirable for the developing world. We are currently exploring reasonable alternative options such as corneal autografts, xenografts, noncorneal autologous tissues, and laboratory-made tissue constructs, as well as modifications to corneal allografts, such as deep-freezing, glycerol-dehydration, gamma irradiation, and cross-linking. These alternative tissue carriers for the B-KPro are discussed with special regard to safety, practicality, and cost for the developing world.
PMCID: PMC3859260  PMID: 24371522

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