Finding an Optimal Corneal Xenograft Using Comparative Analysis of Corneal Matrix Proteins Across Species.

Numerous animal species have been proposed as sources of corneal tissue for obtaining decellularized xenografts. The selection of an appropriate animal model must take into consideration the differences in the composition and structure of corneal proteins between humans and other animal species in order to minimize immune response and improve outcome of the xenotransplant. Here, we compared the amino-acid sequences of 16 proteins present in the corneal stromal matrix of 14 different animal species using Basic Local Alignment Search Tool, and calculated a similarity score compared to the respective human sequence. Primary amino acid structures, isoelectric point and grand average of hydropathy (GRAVY) values of the 7 most abundant proteins (i.e. collagen α-1 (I), α-1 (VI), α-2 (I) and α-3 (VI), as well as decorin, lumican, and keratocan) were also extracted and compared to those of human. The pig had the highest similarity score (91.8%). All species showed a lower proline content compared to human. Isoelectric point of pig (7.1) was the closest to the human. Most species have higher GRAVY values compared to human except horse. Our results suggest that porcine cornea has a higher relative suitability for corneal transplantation into humans compared to other studied species.

Cost effectiveness of the type II Boston keratoprosthesis.

PURPOSE: 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. RESULTS: Using the current parameters, the cost utility of KPro from third-party insurer (Medicare) perspective was 63,196 $/quality-adjusted life year . CONCLUSION: 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.

Neutrophil and eosinophil participation in atopic and vernal keratoconjunctivitis.

PURPOSE: A retrospective study was conducted at three centers to examine the participation of neutrophils and eosinophils in the inflammatory processes associated with atopic keratoconjunctivitis (AKC) and vernal keratoconjunctivitis (VKC). METHODS: Conjunctival specimens were obtained from four patients with AKC, six with VKC, and five normal subjects. Indirect immunofluorescent staining was used to localize neutrophil elastase (NE) and eosinophil granule major basic protein (MBP) in serial sections of all specimens. RESULTS: Specimens from both AKC and VKC patients revealed extracellular deposition of NE and MBP. Control specimens showed no or minimal extracellular NE, and no MBP. Statistical analysis demonstrated significantly greater extracellular MBP deposition in AKC specimens compared to controls (p = 0.009), and VKC specimens showed significantly greater staining for both extracellular MBP (p = 0.005) and NE (p = 0.006). CONCLUSIONS: These results suggest that neutrophils, in addition to eosinophils, play an active role in the pathogenesis of AKC and VKC as evidenced by the extracellular deposition of their specific granule proteins.

Histopathology of explanted collar button keratoprostheses: a clinicopathologic correlation.

PURPOSE: To compare the histopathology of three PMMA collar button type keratoprosthesis (KPro)/corneal specimens, explanted due to various complications, with that from one KPro/corneal specimen taken postmortem from an otherwise "healthy" enucleated eye. METHODS: Patient 1 (chemical injury) had no problems for 3 years after KPro placement; the entire eye was obtained postmortem. Patient 2 (repeated graft failures, nonautoimmune disease) developed an "unlaserable" retroprosthesis membrane 4 months after KPro placement. A new KPro was placed. Patient 3 [ocular cicatricial pemphigoid (OCP)] developed tissue melt at the KPro-cornea interface 7 months after KPro placement, and the KPro was replaced. Patient 4 (OCP) developed progressive corneal melt around the KPro 3.5 years after placement resulting in replacement. All KPro/cornea specimens were processed and sectioned for histology with the KPro in place. RESULTS: All patients exhibited growth of corneal or conjunctival derived epithelium under the KPro front plate. In patients 1 and 2, no epithelial downgrowth was noted and the keratocyte density appeared normal with few inflammatory cells present. Dense fibrous tissue was present behind the KPro in patient 2. Patients 3 and 4 showed massive inflammatory cell infiltration and tissue necrosis with "melt" adjacent to the stem resulting in epithelial downgrowth. CONCLUSIONS: Corneal inflammation and degradation after KPro placement correlate well with the preoperative diagnostic category. Patients with immune-related corneal surface disease can exhibit marked inflammatory responses leading to necrosis, stromal melting, and the formation of an epithelial fistula. In contrast, patients without autoimmune corneal disease demonstrate a remarkably noninflamed cornea with intact keratocytes and without epithelial ingrowth, commensurate with their clinical appearance.

Keratoprosthesis: an update.

Porous polytetrafluoroethylene and polyurethane skirt materials, as well as copolymers of poly (2-hydroxyethyl methacrylate), have shown promise in approaching the goal of a "biointegratable" keratoprosthesis. A novel fixation method that uses scleral haptics also has been introduced to increase stability. An all silicone device that can be sewn into position has been used successfully, temporarily, during vitreoretinal procedures. The prognosis of keratoprosthesis (KPro) procedures depends on the preoperative diagnosis: graft failure-noncicatrizing disease>ocular cicatricial pemphigoid>chemical burns>Stevens-Johnson syndrome. The likelihood of endophthalmitis after KPro surgery follows this scheme. Causative organisms tend to be gram-positive. Modified vitreoretinal techniques also have been developed, allowing successful treatment of posterior segment complications. The science of keratoprosthesis is advancing more rapidly than in previous years. However, use of KPro to address complicated corneal blindness worldwide remains limited. The authors conducted an English language literature review from January 1, 2000 to April 1, 2001 and describe advances of note in the field of keratoprosthesis design, materials, and medical and surgical management.

Amniotic membrane inlay and overlay grafting for corneal epithelial defects and stromal ulcers.

OBJECTIVES: To determine the effect of amniotic membrane transplantation (AMT) on persistent corneal epithelial defects (PEDs) and to compare the efficacy between inlay and overlay techniques. METHODS: Thirty patients (30 eyes) underwent AMT for PED. The use of AMT was restricted to patients in whom all previous measures, including bandage contact lens and tarsorrhaphy, had failed. The amniotic membrane was placed on the surface of the cornea in overlay (group A) or inlay (group B) fashion. RESULTS: The PED healed after the first AMT in 21 eyes (70%) within an average of 25.5 days after surgery and recurred in 6 eyes (29%). Among the 22 eyes treated with an overlay AMT (group A), the PED healed after the first AMT in 14 eyes (64%) within an average of 24.5 days and recurred in 4 eyes (29%). Among the 8 eyes treated with an inlay AMT (group B), the PED healed within an average of 27.4 days after AMT, which did not statistically significantly differ from group A (P = .72). The PED healed after the first AMT in 7 eyes (88%) and recurred in 2 (29%) of 7 eyes. CONCLUSIONS: The AMT can be helpful in the treatment of PED in which all other conventional management has failed. However, the success rate in our study was not as high as that previously reported, and our results showed a high incidence of recurrences of epithelial defects. We did not find any difference between overlay and inlay techniques in terms of healing time and recurrence rate.

Endophthalmitis after keratoprosthesis: incidence, bacterial causes, and risk factors.

OBJECTIVES: To determine the rate of endophthalmitis in a group of patients with keratoprostheses and to analyze possible risk factors. METHODS: A total of 108 patient eyes, operated on between 1990 and 2000 with double-plated keratoprostheses, were analyzed with regard to the surface flora, the incidence and cause of bacterial endophthalmitis or sterile vitreitis, the keratoprosthesis design, prophylactic antibiotics, concomitant immunosuppression, and preoperative diagnosis. RESULTS: Surveillance cultures were obtained from 30 uninfected eyes. The flora was similar to that reported in the normal population and did not vary significantly with time. Thirteen cases of bacterial endophthalmitis occurred 2 to 46 months postoperatively in the patient population that had been followed up for 2 months to 17 years (average, 3 years 4 months). The incidence was 39% in 13 patients with Stevens-Johnson syndrome, 19% in 27 patients with ocular cicatricial pemphigoid, and 7% in 28 patients with ocular burns. Only 1 of the other 40 cases (consisting mostly of repeated graft failures in noncicatrizing conditions) developed endophthalmitis; this patient had a filtering bleb. All endophthalmitis pathogens were gram positive: Streptococcus pneumoniae, 23%; other streptococci, 39%; Staphylococcus aureus, 23%; and Staphylococcus epidermidis, 15%. CONCLUSIONS: The most important risk factor for endophthalmitis after these keratoprostheses was found to be preoperative diagnosis. The rate of infection was very high in Stevens-Johnson syndrome and ocular cicatricial pemphigoid, moderate in chemical burns, and low in noncicatrizing corneal disease.

Candidal endophthalmitis after keratoplasty.

PURPOSE: To report a case of explosive fungal endophthalmitis after penetrating keratoplasty and to review additional published and unpublished cases to consider possible strategies for prevention. METHODS: Records of this patient with postkeratoplasty candidal endophthalmitis and previously reported cases of postkeratoplasty candidal endophthalmitis were reviewed. Additional information of 26 unpublished cases was obtained from the Eye Bank Association of America. RESULTS: After standard keratoplasty, the patient developed precipitous endophthalmitis on the second postoperative day. Abundant contamination with Candida was found in the residual donor corneoscleral rim, and Candida albicans was isolated from the aqueous humor of the recipient. Despite therapy with local antimicrobial agents, intraocular amphotericin B, and systemic fluconazole, the patient had a poor outcome with hand-motion visual acuity. Of the 44 collected cases of postkeratoplasty candidal endophthalmitis, 40 (91%) had the same organism cultured from the donor rim or medium. Forty-three donor corneas had been preserved in cold storage medium at 4 degrees C. Of 15 cases in which the outcome was available, 9 (60%) resulted in visual acuity of 20/200 or worse. CONCLUSION: Case reports confirm the occurrence of donor-to-host transmission of postkeratoplasty candidal endophthalmitis. Despite the low reported incidence, the poor prognosis of the affected eye in the ajority of these cases suggests the need for antifungal supplementation of cold preservation media and other preventative strategies.

Keratoprosthesis: preoperative prognostic categories.

PURPOSE: Recent advances aimed at preventing and treating complications after keratoprosthesis surgery have improved prognosis, but it has been suspected that various preoperative diagnoses may carry substantially different postoperative outcomes. This article attempts to clarify the ranking of prognostic categories for patients undergoing keratoprosthesis surgery. METHODS: A retrospective review of the outcome in a recent series of 63 patient eyes operated at the Massachusetts Eye and Ear Infirmary between 1990 and 1997 and followed up for a minimum of 21 months. Anatomic retention of the device and the loss of vision caused by complications were recorded. The patients were divided into four categories according to preoperative cause. RESULTS: Anatomically, one keratoprosthesis extruded spontaneously. Another 10 were permanently removed because of complications. Of the 63 eyes, 10 never achieved a visual acuity of at least 20/200 vision because of preexisting retinal or optic nerve damage. The remaining 53 had a visual acuity of 20/200 to 20/20 as follows: Stevens-Johnson syndrome (n = 7), after 2 years: 33%, after 5 years: 0%; chemical burn (n = 17), after 2 years: 64%, after 5 years: 25%; ocular cicatricial pemphigoid (n = 20), after 2 years: 72%, after 5 years: 43%; graft failure in noncicatrizing conditions (dystrophies, degenerations, or bacterial or viral infections) when a repeat graft was expected to have a poor prognosis (n = 19), after 2 years: 83%, after 5 years: 68%. The difference in outcome between the Stevens-Johnson syndrome outcome group and the graft failure group or the ocular cicatricial pemphigoid group was statistically significant. In the group of 53 eyes, visual acuity was restored to 20/200 to 20/20 for a cumulative total of 138 years. CONCLUSION: Outcome of the keratoprosthesis surgery varied markedly with preoperative diagnosis. Most favorable was graft failures in non-cicatrizing conditions, whereas Stevens-Johnson syndrome was the worst. Ocular cicatricial pemphigoid and chemical burns occupied a middle ground. The difference between the groups seemed to correlate with the degree of past preoperative inflammation.

Survey of patients with granular, lattice, avellino, and Reis-Bücklers corneal dystrophies for mutations in the BIGH3 and gelsolin genes.

OBJECTIVES: To search for novel mutations that cause corneal stromal dystrophies and to confirm or revise the clinical diagnosis of patients with these mutations. PATIENTS: Through review of the records of the Cogan Eye Pathology Laboratory at the Massachusetts Eye and Ear Infirmary, Boston, and of clinical records, we ascertained 14 unrelated patients with the clinical or histopathologic diagnosis of granular (3 cases), Avellino (5 cases), lattice (5 cases), or Reis-Bücklers (1 case) corneal dystrophy. METHODS: Clinical records and histopathologic findings of the index patients and their relatives were reviewed. Patients and selected relatives donated a blood sample from which leukocyte DNA was purified and assayed for mutations in the BIGH3 gene and, in 2 patients, the gelsolin gene, using the polymerase chain reaction and direct genomic sequencing. RESULTS: All index patients with the diagnosis of granular dystrophy or Avellino dystrophy had the missense mutation Arg555Trp or Arg124His, respectively, previously reported in the BIGH3 gene. Of the 5 index patients with a prior diagnosis of lattice dystrophy, 2 had the originally reported lattice mutation (Arg124Cys) in the BIGH3 gene, 1 had a more recently reported missense mutation (His626Arg) in the same gene, 1 had the missense mutation Asp187Asn in the gelsolin gene, and 1 had no detected mutation in either gene. Affected members of the family with Reis-Bücklers dystrophy did not carry the previously reported mutations Arg555Gln or Arg124Leu but instead carried a novel missense mutation Gly623Asp in the BIGH3 gene. CONCLUSIONS: Molecular genetic analysis can improve the accuracy of diagnosis of patients with corneal dystrophies. Two patients with a prior diagnosis of lattice corneal dystrophy had their diagnosis changed to gelsolin-related amyloidosis (1 case) or secondary, nonhereditary localized amyloidosis (1 case). A novel mutation in the BIGH3 gene that causes Reis-Bücklers dystrophy was uncovered through this analysis, and another recently reported novel mutation was encountered. These findings serve to expand our knowledge of the spectrum of pathogenic mutations in BIGH3.

Innovations in keratoprosthesis: proved and unproved.

Progress in the notoriously slow and difficult field of KPro has gained speed during the last decade, and interest among corneal surgeons has been increasing slowly. Recent advances aimed at preventing complications and treating early complications after KPro surgery have improved the prognosis. In retrospect, several factors have proved critical to this progress. Organic chemistry has given us PMMA--an invaluable material--watery clear and inert. This material may be surpassed in the future, but it has served us well during the last half-century. KPro designs are undoubtedly important, although their role probably has been overstated. Temporary postoperative tissue coverage has proved its value. Antiinflammatory substances are absolutely vital, and enzyme inhibitors show promise. Glaucoma shunts are definitely effective in preventing glaucoma in some (but not all) patients. Finally, frequent follow-ups--more than after most other ocular surgeries--and early repairs of complications are mandatory. With recent resurgence in interest and further developments, the future of KPro surgery should be bright.

Keratoprosthesis in pemphigoid and Stevens-Johnson syndrome.

Keratoprosthesis was implanted in 17 eyes with ocular pemphigoid and 7 eyes with Stevens-Johnson syndrome and followed for 6 months to 6 years. Visual outcomes and complications were compared. Pemphigoid was found to have a much better prognosis than did Stevens-Johnson syndrome. Keratoprosthesis is now firmly indicated in elderly pemphigoid patients whose vision in both eyes has become reduced to hand movements or less due to a corneal opacity.

Glaucoma associated with keratoprosthesis.

OBJECTIVE: This study aimed to review the authors clinical experience with glaucoma associated with keratoprosthesis in patients with severe corneal disease. DESIGN: The study design was a retrospective review of case series. PARTICIPANTS: The authors studied 55 eyes in 52 patients with keratoprostheses with follow-up of 21 +/- 16 months (range, 3-77 months). INTERVENTION: Glaucoma drainage devices were implanted in 36 eyes (35 Ahmed valves, 1 Krupin valve) with 21 +/- 15 months' follow-up (range, 3-64 months). MAIN OUTCOME MEASURES: Clinical outcome assessment included vision, intraocular pressure (IOP), visual fields, optic disc appearance, and identification of complications. RESULTS: Glaucoma was found in the majority (64%) of eyes treated with keratoprostheses, identified in 20 eyes (36%) before surgery and an additional 15 eyes (28%) after surgery. Of the 36 eyes treated with glaucoma drainage devices, IOP was controlled in 29 eyes (81%), with 9 eyes (25%) requiring additional medications. Continued progression of glaucoma occurred in 5 (14%) of 36 eyes with keratoprostheses and glaucoma drainage implants (4 of these eyes had advanced glaucomatous optic nerve damage before surgery). There were nine nonvision-threatening complications due to drainage implants. Compared with the preoperative visual acuity, vision was markedly improved in 63%, unchanged in 17%, and worse in 20% of eyes after keratoprosthesis surgery. CONCLUSION: Elevation of IOP is common in patients with keratoprosthesis, and prevention or treatment with glaucoma drainage implants is effective.

Fabrication of a keratoprosthesis.

For patients with opaque corneas that have a poor prognosis when using regular corneal transplants, a clear plastic "window" in the form of a keratoprosthesis may offer the only hope of usable vision. Various forms of such devices have been used for many years with varying degrees of success. The design, fabrication, and optical testing of two variations of a polymethylmethacrylate (PMMA) keratoprosthesis are described. Type 1 consists of a twin-plate collarbutton-style design that is used in eyes that have sufficient tear fluid production to maintain wetting of the anterior surface of the eye. Type 2 is of a similar design, with an added anterior cylinder that protrudes through a permanently closed eyelid, and is used in end-stage dry eyes.

Some factors influencing outcome after keratoprosthesis surgery.

Eleven patients with severe corneal disease have been operated with a collar-button-shaped keratoprosthesis and have been followed for 9-36 months. Two of the devices have been removed, but the remainder are securely in place. Six of the patients have benefitted substantially in terms of improved vision. The complications have been reviewed, and some factors for success have been identified. Thus, to keep the keratoprosthesis temporarily buried beneath tissue (conjunctiva or skin), application of collagenase-suppressing medication and reduction of evaporative damage to the wound around the device seem particularly important.