The Boston Keratoprosthesis in severe ocular trauma

Nanohydroxyapatite Coating Attenuates Fibrotic and Immune Responses to Promote Keratoprosthesis Biointegration in Advanced Ocular Surface Disorders

Keratoprosthesis (KPro) implantation is frequently the only recourse for patients with severe corneal disease. However, problems arise due to inadequate biointegration of the KPro, particularly the PMMA optical cylinder, such as tissue detachment, tissue melting, or eye-threatening infection in the interface. Here, using the AuroKPro as a model prosthesis, a surface functionalization approach─coating the optical cylinder with nanohydroxyapatite (nHAp)─was trialed in rabbit eyes with and without a proceeding chemical injury. In chemically injured eyes, which simulated total limbal epithelial stem cell deficiency, clear benefits were conferred by the coating. The total modified Hackett-McDonald score and area of tissue apposition differences 12 weeks after implantation were 5.0 and 22.5%, respectively. Mechanical push-in tests revealed that 31.8% greater work was required to detach the tissues. These differences were less marked in uninjured eyes, which showed total score and tissue apposition differences of 2.5 and 11.5%, respectively, and a work difference of 23.5%. The improved biointegration could be contributed by the attenuated expression of fibronectin (p = 0.036), collagen 3A1 (p = 0.033), and α-smooth muscle actin (p = 0.045)─proteins typically upregulated during nonadherent fibrous capsule envelopment of bioinert material─adjacent to the optical cylinders. The coating also appeared to induce a less immunogenic milieu in the ocular surface tissue, evidenced by the markedly lower expression of tear proteins associated with immune and stimulus responses. Collectively, the level of these tear proteins in eyes with coated prostheses was 1.1 ± 13.0% of naïve eyes: substantially lower than with noncoated KPros (246.5 ± 79.3% of naïve, p = 0.038). Together, our results indicated that nHAp coating may reduce the risk of prosthesis failure in severely injured eyes, which are representative of the cohort of KPro patients.

The prophylactic value of TNF-α inhibitors against retinal cell apoptosis and optic nerve axon loss after corneal surgery or trauma

BACKGROUND AND PURPOSE

Late secondary glaucoma is an often-severe complication after acute events like anterior segment surgery, trauma and infection. TNF-α is a major mediator that is rapidly upregulated, diffusing also to the retina and causes apoptosis of the ganglion cells and degeneration of their optic nerve axons (mediating steps to glaucomatous damage). Anti-TNF-α antibodies are in animals very effective in protecting the retinal cells and the optic nerve-and might therefore be useful prophylactically against secondary glaucoma in future such patients. Here we evaluate (1) toxicity and (2) efficacy of two TNF-α inhibitors (adalimumab and infliximab), in rabbits by subconjunctival administration.

METHODS

For drug toxicity, animals with normal, unburned corneas were injected with adalimumab (0.4, 4, or 40 mg), or infliximab (1, 10, or 100 mg). For drug efficacy, other animals were subjected to alkali burn before such injection, or steroids (for control). The rabbits were evaluated clinically with slit lamp and photography, electroretinography, optical coherence tomography, and intraocular pressure manometry. A sub-set of eyes were stained ex vivo after 3 days for retinal cell apoptosis (TUNEL). In other experiments the optic nerves were evaluated by paraphenylenediamine staining after 50 or 90 days. Loss of retinal cells and optic nerve degeneration were quantified.

RESULTS

Subconjunctival administration of 0.4 mg or 4.0 mg adalimumab were well tolerated, whereas 40.0 mg was toxic to the retina. 1, 10, or 100 mg infliximab were also well tolerated. Analysis of the optic nerve axons after 50 days confirmed the safety of 4.0 mg adalimumab and of 100 mg infliximab. For efficacy, 4.0 mg adalimumab subconjunctivally in 0.08 mL provided practically full protection against retinal cell apoptosis 3 days following alkali burn, and infliximab 100 mg only slightly less. At 90 days following burn injury, control optic nerves showed about 50% axon loss as compared to 8% in the adalimumab treatment group.

CONCLUSIONS

Subconjunctival injection of 4.0 mg adalimumab in rabbits shows no eye toxicity and provides excellent neuroprotection, both short (3 days) and long-term (90 days). Our total. accumulated data from several of our studies, combined with the present paper, suggest that corneal injuries, including surgery, might benefit from routine administration of anti-TNF-α biologics to reduce inflammation and future secondary glaucoma.

[Long-term visual outcomes of Boston type I keratoprosthesis in Canada]

BACKGROUND/PURPOSE

To evaluate long-term visual outcomes of Boston type I keratoprosthesis (KPro) surgery and identify risk factors for visual failure.

METHODS

Single surgeon retrospective cohort study including 85 eyes of 74 patients who underwent KPro implantation to treat severe ocular surface disease, including limbal stem cell deficiency, postinfectious keratitis, aniridia and chemical burns. Procedures were performed at the Centre hospitalier de l'Université de Montréal from October 2008 to May 2012. All patients with at least 5 years of follow-up were included in the analysis, including eyes with repeated KPro. Main outcome measures were visual acuity (VA), visual failure, defined as a sustained VA worse than the preoperative VA, postoperative complications, and device retention.

RESULTS

Mean follow-up was 7.2±1.3 years (±SD). Mean VA was 2.1±0.7 (logarithm of minimal angle resolution) preoperatively and 1.9±1.2 at last follow-up. In total, 2.4% of patients had VA better than 20/200 preoperatively vs. 36.5% at last follow-up. Maintenance of improved postoperative VA was seen in 61.8% of eyes at 7 years. Preoperative factors associated with visual failure were known history of glaucoma (HR=2.7 [1.2 to 5.9], P=0.02) and Stevens-Johnson syndrome (HR=7.3 [2.5 to 21.4], P<0.01). Cumulative 8-year complication rates were 38.8% retroprosthetic membrane formation, 25.9% hypotony, 23.5% new onset glaucoma, 17.6% retinal detachment, 8.2% device extrusion and 5.9% endophthalmitis. The majority (91.8%) of eyes retained the device 8 years after implantation.

CONCLUSION

Nearly two-thirds of patients exhibited improved VA 7 years after KPro implantation. Preoperative risk factors for visual failure were known glaucoma and Stevens-Johnson syndrome.

Probing mechanisms and improving management of glaucoma following Boston keratoprosthesis surgery

ENGLISH SUMMARY

Corneal blindness is a leading cause of visual impairment worldwide. The most common treatment is to replace the diseased cornea by standard corneal transplantation. In eyes at high risk of graft failure, the Boston keratoprosthesis type 1 (KPro) can be used to restore vision and is currently the most frequently used artificial cornea in the world. However, glaucoma is a well-known complication of KPro surgery and is the most important threat to vision in KPro-implanted eyes (paper I). This chronic disease is influenced by elevated intraocular pressure (IOP) and damages the optic nerve, leading to progressive vision loss. In KPro patients, glaucoma is highly prevalent and extremely challenging to manage, yet its exact cause remains unknown. The overall purpose of this PhD Thesis (Geoffrion, 2021) was to better understand the mechanisms and how to improve management of glaucoma after KPro implantation. The approaches used in this thesis included investigating one of the largest KPro patient cohorts in North America, with a total of 157 operated patients at that time, as well as studying KPro surgery and outcomes in mice. The first objective was to identify risk factors for glaucoma development and progression after KPro implantation (paper II). Multivariate logistic regression revealed that high preoperative IOP signals a higher risk for both glaucoma development and progression. Stromal and endothelial corneal disorders were less associated with glaucoma progression, while autoimmune and ocular surface diseases precipitated glaucoma development. Second, there is no objective evidence that indicates the best order for glaucoma surgeries and KPro implantation. By comparing medical and surgical management in KPro eyes with either preexisting or de novo glaucoma (paper III), we showed that glaucoma surgery may be performed before or at the time of KPro in eyes with preexisting glaucoma to limit progression without increasing complications. In eyes with de novo glaucoma, glaucoma surgery did not increase complications compared with medications. Third, among glaucoma surgery interventions, the two most frequently implanted glaucoma drainage devices were compared in KPro patients (paper IV). Compared with the Ahmed glaucoma valve, the Baerveldt glaucoma implant was associated with lower failure rates, without increased postoperative complications. Fourth, even with aggressive management, many KPro patients suffer from progressive optic nerve damage, sometimes despite normal IOP. Inflammatory cytokines play an important role in glaucomatous optic neuropathy, but their role in KPro-associated glaucoma is still unknown. By analysing tear fluid of KPro patients by multiplex bead immunoassay (paper V), we identified that cytokines TNF-a, IL-1b, FGF-basic and IFN-g were elevated in KPro patients with glaucoma compared to those without. These cytokines correlated with optic nerve excavation and IOP. For the first time in humans, these results concorded with the elevations of TNF-a and IL-1b documented in the mouse KPro model. Ocular surface inflammation may thus reflect the inflammatory processes that perpetuate glaucoma damage years after KPro surgery. Fifth, we determined that miniaturized mouse KPro implantation requires extensive practice to be used as a reproducible model of glaucoma post-KPro (paper VI). KPro animal models with larger eyes and a full-thickness, 360-degree corneal excision should be prioritized to best validate human outcomes. In conclusion, glaucoma in KPro eyes is a long-lasting and multifactorial process. Most probable mechanisms combine IOP-independent inflammation mediated by TNF-a and IL-1b that prolong glaucoma damage, together with post-surgical angle closure elevating the IOP. Altogether, our results inform glaucoma risk profiling of transplant recipients, improvement of surgical management of KPro patients with glaucoma and development of targeted treatments to minimize glaucomatous damage after KPro. Ultimately, this work has the potential to preserve the vision of thousands of patients who undergo KPro surgery every year worldwide and to provide insight for the role of inflammation in other diseases involving neuronal damage. RÉSUMÉ (FRENCH SUMMARY): La cécité cornéenne est l'une des causes les plus importantes de déficience visuelle dans le monde. Le traitement usuel est de remplacer la cornée malade par une greffe de cornée traditionnelle. Dans les yeux à haut risque d'échec de greffe, la kératoprothèse de Boston de type 1 (KPro) peut rétablir la vision et est la cornée artificielle la plus utilisée au monde. Cependant, le glaucome est une complication importante de la KPro (papier I). Cette maladie chronique est influencée par une pression intraoculaire (PIO) élevée et endommage le nerf optique, menant à une perte de vision. Chez les patients avec KPro, le glaucome est fréquent et difficile à contrôler, mais sa cause exacte demeure inconnue. L'objectif principal de cette thèse est de découvrir les mécanismes et d'optimiser la prise en charge du glaucome après l'implantation de la KPro. Pour ce faire, nous avons investigué l'une des plus grandes cohortes de patients KPro en Amérique du Nord avec un total de 157 patients, ainsi qu'un groupe de souris ayant reçu une implantation de kératoprothèse. Le premier but était d'identifier les facteurs de risque pour le développement et la progression du glaucome après la KPro (papier II). Par régression logistique multivariée, nous avons démontré qu'une PIO préopératoire élevée mène à un plus grand risque de développement et de progression du glaucome. Les maladies cornéennes stromales ou endothéliales sont moins associées à une progression, alors que les maladies autoimmunes ou de la surface oculaire précipitent le développement du glaucome. Deuxièmement, il n'existe aucune donnée objective pour indiquer le meilleur ordre des chirurgies de glaucome et de KPro. En comparant les traitements médicaux et chirurgicaux des yeux KPro avec glaucome (papier III), nous avons démontré que les chirurgies de glaucome peuvent limiter la progression en étant effectuées avant ou pendant l'implantation de KPro dans les yeux avec glaucome préexistant, sans augmenter les complications. Dans le glaucome de novo, les chirurgies de glaucome n'augmentent pas les complications en comparaison aux médicaments. Troisièmement, les deux implants de glaucome les plus communs ont été étudiés chez les patients KPro (papier IV). Comparé à la valve Ahmed, l'implant Baerveldt est associé à des taux d'échec plus bas, sans augmentation des complications. Quatrièmement, même avec une prise en charge agressive, plusieurs patients KPro souffrent de glaucome qui progresse, parfois sans PIO élevée. Les cytokines inflammatoires jouent un rôle dans la pathophysiologie du glaucome, mais leur rôle dans le glaucome associé à la KPro est inconnu. En analysant les larmes de patients KPro (papier V), nous avons identifié que les cytokines TNF-a, IL-1b, FGF-basic et IFN-g sont élevées chez les patients KPro avec glaucome comparé à ceux sans glaucome. Ces cytokines corrèlent avec l'excavation du nerf optique et la PIO. Pour la première fois chez les humains, ces résultats concordent avec les niveaux élevés de TNF-a et IL-1b documentés dans le modèle murin de KPro. L'inflammation de la surface oculaire pourrait donc refléter les processus inflammatoires qui perpétuent le dommage glaucomateux. Cinquièmement, nous avons déterminé que l'implantation de la KPro miniature chez la souris requiert beaucoup de pratique pour être utilisé comme modèle de glaucome post-KPro (papier VI). Des modèles animaux avec des yeux plus larges et une excision cornéenne de pleine épaisseur sur 360 degrés devraient être priorisés pour valider les résultats chez l'humain. En conclusion, le glaucome associé à la KPro est un processus multifactoriel qui persiste à long terme. Les mécanismes probables combinent l'inflammation médiée par TNF-a et IL-1b et une fermeture de l'angle qui augmente la PIO. Nos résultats contribuent à établir les facteurs de risque de glaucome pour les receveurs de KPro, à améliorer leur prise en charge et à développer des thérapies ciblées. Ce travail a le potentiel de préserver la vision de milliers de patients recevant une KPro chaque année dans le monde et d'aider à mieux comprendre le rôle de l'inflammation dans d'autres maladies avec atteinte neuronale.

The treatment of end-stage corneal disease: penetrating keratoplasty compared with Boston type 1 keratoprosthesis

Penetrating keratoplasty (PKP) yields excellent results for restoring vision in end-stage corneal diseases. However, its success is limited to high-risk diseases such as aniridia, chemical burns, autoimmune corneal diseases, and herpetic eye disease. Boston type 1 keratoprosthesis (BKPro) offers another option to these patients. Since 1992, improvements in perioperative management and device construction have significantly increased the use of BKPro worldwide and challenged the therapeutic role of PKP in these patients. This review aims to evaluate BKPro's place in the treatment algorithm of these high-risk patients to assist surgeons' decision-making. PKP and BKPro are compared in three outcome categories: visual acuity, graft retention and failure, and complications profile. Special attention is given to comparing secondary BKPro versus repeated PKP as well as primary BKPro versus primary PKP. We conclude that secondary BKPro bears a better prognosis than repeated PKP in most high-risk patients. Similarly, primary BKPro likely confers improved outcomes over primary PKP in most high-risk recipients. However, current evidence is based on retrospective designs, and controlled prospective randomized trials are required to validate these conclusions.

Clinical Experience in Patients with Ocular Burns Treated with Boston Type I Keratoprosthesis Implantation with or Without Prophylactic Ahmed Glaucoma Valve Implantation

Introduction

To compare outcomes in eyes with ocular burns following Boston Type I keratoprosthesis (KPro) implantation with and without prophylactic pars plana tube surgery.

Methods

A retrospective review of patients with ocular burns who underwent KPro surgery at Zhongshan Ophthalmic Center was performed. Twenty-six eyes of 26 patients without a preoperative diagnosis of glaucoma before KPro surgery met the inclusion criteria. Preoperative glaucoma was defined as a history of a durable elevated intraocular pressure (IOP) ≥ 25 mmHg at different time points, which resulted in the introduction of anti-glaucoma medication or surgical intervention. Sixteen eyes underwent KPro alone (Group 1), and 10 eyes received KPro with prophylactic pars plana tube surgery (Group 2).

Results

Group 1 and Group 2 were similar in the proportions of the ocular burn type and preoperative clock hours of peripheral anterior synechiae by ultrasound biomicroscopy (1.88 ± 1.63 vs. 2.30 ± 1.83; P = 0.54). Before KPro surgery, 62.5% of eyes in Group 1 and 50.0% of eyes in Group 2 had intraocular surgeries (P = 0.53). The follow-up time was 18 months. At the final follow-up time, the two groups had similar visual acuity (1.34 ± 0.87 logMAR, 1.03 ± 0.71 logMAR; P = 0.35) and eyes with a C/D ratio ≥ 0.8 (7/16, 2/10; P = 0.21), but more eyes in Group 1 developed glaucoma de novo than eyes in Group 2 (62.5%, 20%; P = 0.04) and had undergone secondary glaucoma surgery after KPro implantation (7/16 vs. 0/10; P = 0.02).

Conclusion

In eyes injured with ocular burns, KPro implantation with prophylactic pars plana tube surgery may be a feasible option to rehabilitate visual acuity and decrease the incidence of glaucoma de novo.

Glaucoma Risk Factors and Outcomes Following Boston Keratoprosthesis Type 1 Surgery

PURPOSE

To evaluate glaucoma risk factors and associated outcomes of the Boston keratoprosthesis type I (KPro).

DESIGN

Clinical case-control study.

METHODS

This is a single-center study of 140 eyes of 118 patients who underwent KPro surgery between October 2008 and March 2017 by a single surgeon. A total of 118 eyes of 118 patients with at least 6 months of follow-up were analyzed to account for intereye correlation. Patients without glaucoma were compared to those diagnosed with glaucoma, which included treatment with intraocular pressure (IOP)-lowering medications or glaucoma surgery. A subgroup analysis compared eyes with pre-KPro glaucoma with those with post-KPro glaucoma. Statistical analysis was performed using univariate and multivariate analyses and Kaplan-Meier survival curves. Main outcome measures were glaucoma diagnosis and progression. Other outcomes included demographics, preoperative diagnosis, best-corrected visual acuity, IOP, cup-to-disc ratio progression and postoperative complications.

RESULTS

The mean age at surgery was 60.7 ± 16.7 years, with a follow-up of 6.9 ± 3.2 years. De novo KPro glaucoma incidence was 24% (n = 28/118), equivalent to 3.4 cases per 100 eye-years, with onset at 2.1 ± 2.2 postoperative years. A total of 17 of 118 eyes (14%) did not have glaucoma. Multiple logistic regression showed that high preoperative IOP was a predictor of higher rates of glaucoma development (odds ratio [OR] = 1.538, 95% confidence interval [CI] = 1.030-2.297, P = .035) and progression (OR = 1.450, 95% CI = 1.084-1.937, P = .012). Stromal and endothelial disorders were protective preoperative diagnoses for glaucoma progression after KPro (OR = 0.002, 95% CI = 0.000-0.227, P = .010). A greater proportion of eyes with autoimmune and ocular surface diseases developed de novo glaucoma after KPro compared with other preoperative diagnoses (P < .05). A total of 45% of glaucomatous KPro eyes suffered postoperative glaucoma progression. The mean final best-corrected visual acuity of the cohort was 1.76 ± 1.0, with no difference between eyes with and without glaucoma (P > .05). The rate of serious vision-threatening complications was higher in KPro eyes without glaucoma (77%) than in those with glaucoma (41%, P = .006).

CONCLUSIONS

High preoperative IOP signals a higher risk for glaucoma development and progression after KPro surgery. Autoimmune diseases and ocular surface diseases precipitate de novo glaucoma, whereas stromal and endothelial disorders protect against glaucoma progression after KPro. The minority of KPro eyes without glaucoma remain at high risk of complications that can hinder promising visual outcomes. Despite all available treatments and surgical interventions, a majority of eyes will suffer from glaucoma progression, even later during follow-up.

Time to achieve best postoperative visual acuity following Boston keratoprosthesis surgery

BACKGROUND/AIMS

To evaluate the time needed for patients with Boston type 1 keratoprosthesis (KPro) to reach their best-corrected visual acuity (BCVA) and all contributing factors.

METHODS

We retrospectively reviewed 137 consecutive eyes from 118 patients, measured how long they needed to reach their BCVA and looked at factors that might affect this time duration including patient demographics, ocular comorbidities and postoperative complications.

RESULTS

The mean follow-up was 5.49 years. The median time to BCVA postoperatively was 6 months, with 47% of patients achieving their BCVA by 3 months. The mean best achieved logMAR visual acuity was 0.71, representing a gain of 6 lines on the Snellen visual acuity chart. Postoperative glaucoma, retroprosthetic membrane (RPM) and endophthalmitis prolonged this duration. We found no correlation between the following factors and time to BCVA: gender, age, indication for KPro surgery, primary versus secondary KPro, number of previous penetrating keratoplasties, previous retinal surgery, intraoperative anterior vitrectomy and preoperative glaucoma.

CONCLUSION

In our retrospective cohort, the majority of subjects reached their BCVA between 3 and 6 months after KPro implantation. This duration was significantly prolonged by the development of postoperative glaucoma, RPM and endophthalmitis.

Sputter Deposition of Titanium on Poly(Methyl Methacrylate) Enhances Corneal Biocompatibility

Purpose

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.

Methods

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.

Results

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.

Conclusions

Titanium coating of the BK stem generated a mechanically and biologically favorable interface, which may help to enhance corneal stromal adhesion and biocompatibility.

Translational Relevance

Improving the biocompatibility of the BK PMMA stem may improve long-term outcomes of implantation.

Surgical Management of Limbal Stem Cell Deficiency

Treatment of limbal stem cell deficiency is challenging. Multiple options can be adopted according to the underlying cause and the patient and physician preferences. Stem cell transplant is a common treatment modality and several techniques have been described with outcomes varying by the laterality of the condition. Keratoprosthesis is a preferred option for bilateral conditions. Indications for type 1 and type 2 keratoprosthesis differ and the past 2 decades have seen a revolution in the field of keratoprosthesis with encouraging and improved outcomes. Management also includes preventive measures and measures to optimize/stabilize the ocular surface that would go a long way in reducing the deterioration of the ocular surface. The aim of this review is to provide an overview of the currently available techniques and to present a comprehensive algorithm to assist in decision making for unilateral and bilateral limbal stem cell deficiency.

B-scan ultrasound, visual electrophysiology and perioperative videoendoscopy for predicting functional results in keratoprosthesis candidates

BACKGROUND/AIMS

We analysed the ability of B-scan ultrasound, ocular electrophysiology testing and videoendoscopic examination for predicting visual prognosis in Boston Type 1 keratoprosthesis (KPro-1) candidates. Indirect anatomical and electrophysiological findings and results from direct endoscopic evaluations were correlated with postoperative functional data.

METHODS

In this prospective and interventional study, we included 13 individuals who had previously been indicated for Kpro-1 surgery. All subjects underwent preoperative screening, including ophthalmic evaluation, B-scan ultrasound, electrophysiological testing, and perioperative intraocular videoendoscopic evaluation (VE). B-scan ultrasound, electrophysiological testing, and VE evaluation results were categorised as favourable or unfavourable predictors of postoperative functional results according to predefined criteria. The predictability values of B-scan ultrasound, electrophysiological testing, and VE prognostication were calculated based on the visual acuity level achieved.

RESULTS

All surgeries and perioperative VEs were uneventful. Preoperative best-corrected visual acuity (BCVA) ranged from light perception to counting fingers. The 1-year postoperative BCVA was better than 20/200 (satisfactory visual acuity result) in 10 eyes (76.9%) and 20/40 or better in 5 eyes (38.5%). B-scan ultrasound presented a positive predictive value (PPV) of 85.7% for satisfactory postoperative visual acuity, electroretinography showed a PPV of 66.7%, and visual evoked potential presented a PPV of 66.7%. The perioperative VE PPV of a negative finding for satisfactory visual acuity was 100%.

CONCLUSIONS

Fundoscopic visualisation by intraocular VE is a minimally invasive procedure that can be used to predict functional outcomes in keratoprosthesis candidates. This technique demonstrated better prognostication in keratoprosthesis candidates than B-scan ultrasound and electrophysiological testing.

Glaucoma after Ocular Surgery or Trauma: The Role of Infiltrating Monocytes and Their Response to Cytokine Inhibitors

Glaucoma is a frequent and devastating long-term complication following ocular trauma, including corneal surgery, open globe injury, chemical burn, and infection. Postevent inflammation and neuroglial remodeling play a key role in subsequent ganglion cell apoptosis and glaucoma. To this end, this study was designed to investigate the amplifying role of monocyte infiltration into the retina. By using three different ocular injury mouse models (corneal suture, penetrating keratoplasty, and globe injury) and monocyte fate mapping techniques, we show that ocular trauma or surgery can cause robust infiltration of bone marrow-derived monocytes into the retina and subsequent neuroinflammation by up-regulation of Tnf, Il1b, and Il6 mRNA within 24 hours. This is accompanied by ganglion cell apoptosis and neurodegeneration. Prompt inhibition of tumor necrosis factor-α or IL-1β markedly suppresses monocyte infiltration and ganglion cell loss. Thus, acute ocular injury (surgical or trauma) can lead to rapid neuroretinal inflammation and subsequent ganglion cell loss, the hallmark of glaucoma. Infiltrating monocytes play a central role in this process, likely amplifying the inflammatory cascade, aiding in the activation of retinal microglia. Prompt administration of cytokine inhibitors after ocular injury prevents this infiltration and ameliorates the damage to the retina-suggesting that it may be used prophylactically for neuroprotection against post-traumatic glaucoma.

Artificial corneas versus donor corneas for repeat corneal transplants

BACKGROUND

Individuals who have failed one or more full thickness penetrating keratoplasties may be offered repeat corneal surgery using an artificial or donor cornea. An artificial or prosthetic cornea is known as a keratoprosthesis. Both donor and artificial corneal transplantations involve removal of the diseased and opaque recipient cornea (or the previously failed cornea) and replacement with another donor or prosthetic cornea.

OBJECTIVES

To assess the effectiveness of artificial versus donor corneas in individuals who have had one or more failed donor corneal transplantations.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 11); Ovid MEDLINE; Ovid Embase; LILACS (Latin American and Caribbean Health Sciences Literature database); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 4 November 2019.

SELECTION CRITERIA

Two review authors independently assessed reports from the electronic searches to identify randomized controlled trials or controlled clinical trials. Any discrepancies were resolved by discussion or consultation.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. For discussion purposes, we summarized findings from relevant comparative case series. We performed no data synthesis.

MAIN RESULTS

We did not identify any randomized controlled trials or controlled clinical trials comparing artificial corneas with donor corneas for repeat corneal transplantations.

AUTHORS' CONCLUSIONS

The optimal management for those individuals who have failed a conventional corneal transplantation is unknown. Currently, in some centers, artificial corneal devices are routinely recommended after just one graft failure, while in other centers, they are not recommended until after multiple graft failures, or not at all. To date, there have been no controlled trials comparing the visual outcomes and complications of artificial corneal devices (particularly the Boston type 1 keratoprosthesis, which is the most commonly implanted artificial corneal device) with repeat donor corneal transplantation, in order to guide surgeons and their patients. Such a trial is needed and would offer significant benefit to an ever-increasing pool of people with visual disability due to corneal opacification, most of whom are still in productive stages of their lives.

Glaucoma After Corneal Trauma or Surgery-A Rapid, Inflammatory, IOP-Independent Pathway

To review clinical aspects and cellular and molecular steps in the development of long-term glaucoma after corneal surgery or acute trauma—especially the pivotal role of tumor necrosis factor alpha (TNF-α), the rapidity of the secondary damage to the retinal ganglion cells, and the clinical promise of early antiinflammatory intervention.

Systematic Review and Meta-Analysis of the Medium- and Long-Term Outcomes of the Boston Type 1 Keratoprosthesis

PURPOSE

The Boston type 1 keratoprosthesis (KPro), used in patients with high risk of corneal graft failure, is increasingly being used. However, the medium- to long-term outcomes are currently unclear. We analyzed the medium- (2-5 years) and long-term (>5 years) efficacy and safety of the Boston type 1 KPro in terms of visual outcomes, device retention, and postoperative complications.

METHODS

We last searched electronic databases (Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid MEDLINE Epub Ahead of Print, EMBASE, and CENTRAL) on March 31, 2018. Visual outcomes and device retention at 2 and 5 years, alongside postoperative complications, were primary outcome measures.

RESULTS

We identified 407 articles. Thirty studies were included in this systematic review and meta-analysis. The combined proportion of eyes with ≥6/60 vision was 62% at 2 years and 51% at 5 years. The combined retention rate was 88% at 2 years and 74% at 5 years. Retroprosthetic membrane (36.6%) and glaucoma (39.3%) were found to be the most common long-term complications. Very few studies showed visual outcomes or retention rates at 5 years, with results sparse and collectively not meaningful because of small patient numbers and ambiguous reporting of follow-up times.

CONCLUSIONS

The 2-year results indicate that there is a place for the Boston type 1 KPro in the management of corneal blindness. However, there is scarce evidence regarding its medium- and long-term efficacy and safety. The high rate of reported complications necessitates strict patient selection and stringent follow-up.

[Boston keratoprosthesis type 1]

Penetrating keratoplasty is the most commonly performed tissue transplant in the world. However, its success depends on the health of the ocular surface and the intact immune privilege of the eye. In the absence of these two conditions, corneal transplants have an increased failure rate and result in corneal blindness. For more than two hundred years, researchers have been trying to find the best design of the artificial cornea in order to address these cases of severe corneal blindness. Despite previous difficulties, interest in the field has recently been revived, and considerable progress has been made over the last 20 years, to the point where the keratoprosthesis is now considered a primary procedure for some indications and is no longer always a surgery of last resort. In this review, we describe the global and personal experience with Boston keratoprosthesis type 1. It is a relatively new treatment for severe corneal blindness in the context of multiple failed corneal transplants and high-risk conditions. In the last decade, changes in the design, surgical technique, and postoperative management have increased the success rate and popularity of the Boston keratoprosthesis and decreased its complications substantially, making it a safe and effective alternative for certain corneal pathologies. However, some complications persist and require management to improve the visual prognosis of patients with corneal blindness.

Blood Levels of Tumor Necrosis Factor Alpha and Its Type 2 Receptor Are Elevated in Patients with Boston Type I Keratoprosthesis

Purpose: Boston keratoprosthesis (KPro) patients are prone to glaucoma even with well-controlled intraocular pressure (IOP). Recent experimental data have shown that soluble tumor necrosis factor alpha (TNF-α) after ocular injury may contribute to progressive retinal damage and subsequent glaucoma. This study evaluates the blood plasma levels of soluble TNF-α, TNF receptors 1 (TNFR1) and 2 (TNFR2), and leptin in patients with Boston type I KPro. Methods: Venous blood samples were collected from KPro patients with glaucoma (KPro G, n = 19), KPro patients without glaucoma (KPro NoG, n = 12), primary angle closure glaucoma without KPro (PACG, n = 13), and narrow angles without glaucoma or KPro (NA, n = 21). TNF-α, TNFR1, TNFR2, and leptin levels were quantified using the enzyme-linked immunosorbent assay. Erythrocyte sedimentation rate (ESR) was assessed using the Westergren test. Patients with underlying autoimmune conditions or diabetes were excluded from the study. Results: All groups had similar age, body mass index (BMI), IOP, and ESR (p ≥ 0.11). The mean time from KPro surgery to blood draw was 5.3 ± 3.7 years. Compared to NA patients (0.72 ± 0.3 pg/ml), KPro G and KPro NoG patients had higher blood plasma levels of TNF-α (1.18 ± 0.58 pg/ml, p = 0.006; 1.16 ± 0.50 pg/ml, p = 0.04, respectively). Similarly, KPro G patients had higher blood plasma levels of TNFR2 (2768 ± 1368 pg/ml) than NA patients (2020 ± 435 pg/ml, p = 0.048). In multivariate analysis, KPro status remained positively associated with TNF-α levels (β = 0.36; 95% confidence intervals [CI]: 0.14-0.58; p = 0.002) and TNFR2 levels (β = 458.3; 95% CI: 32.8-883.7; p = 0.035) after adjusting for age, gender, BMI, glaucoma status, and ESR. TNFR1 and leptin levels were not significantly different in the study groups. Conclusions: We detected elevated serum levels of TNF-α and TNFR2 in KPro patients. Longitudinal studies are needed to establish TNF-α and TNFR2 as serum biomarkers related to KPro surgery. Abbreviations: BCVA: best corrected visual acuity; BMI: body mass index; CDR: cup-to-disc ratio; EDTA: ethylenediaminetetraacetic acid; ELISA: enzyme-linked immunosorbent assay; ESR: erythrocyte sedimentation rate; HVF: Humphrey visual field; IOP: intraocular pressure; KPro G: keratoprosthesis with glaucoma; KPro NoG: keratoprosthesis without glaucoma; KPro: keratoprosthesis; MD: mean deviation; NA: narrow angle; non-KPro: without keratoprosthesis; PACG: primary angle closure glaucoma; RNFL: retinal nerve fiber layer; TNF-α: tumor necrosis factor alpha; TNFR1: tumor necrosis factor receptor 1; TNFR2: tumor necrosis factor receptor 2.

Improving the practicality and safety of artificial corneas: Pre-assembly and gamma-rays sterilization of the Boston Keratoprosthesis

PURPOSE

To make the Boston keratoprosthesis (B-KPro), together with its carrier corneal graft, more easily procured, transported and stored, as well as less expensive, easier for the surgeon to implant and safer for the patient, it is proposed that the B-KPro-graft combination be pre-assembled by an expert technician, followed by sterilization with gamma ray irradiation (GI) allowing long-term storage at room temperature. For this to be possible, it must be shown that the B-KPro itself (not only the graft) remains unharmed by the irradiation.

METHODS

Polymethyl methacrylate (PMMA) discs and B-KPros were submitted to either ethylene oxide sterilization or different doses of GI. Cell biocompatibility, mechanical strength and optical quality were evaluated. The feasibility of assembling the B-KPro to a corneal graft, and gamma-radiate afterwards, was also assessed.

RESULTS

There were no differences in cell biocompatibility between the samples. The optical evaluation showed high levels of transparency for all the groups. The absorbance of ultraviolet was higher for the groups treated with GI. The mechanical evaluation by nanoindentation showed no alterations of the PMMA discs after GI. The flexure test revealed a similar mechanical behavior. Technically, pre-assembly and GI of the B-KPro revealed no problems.

CONCLUSIONS

Sterilization of B-KPro using GI has no detrimental influence on the device. The pre-assembly of B-KPro to a donor cornea, followed by gamma sterilization, emerges as an efficient and safe procedure.

Boston keratoprosthesis type 1 for limbal stem cell deficiency after severe chemical corneal injury: A systematic review

PURPOSE

To systematically review the published literature on outcomes of Boston keratoprosthesis type 1 for the treatment of limbal stem cell deficiency secondary to severe chemical corneal injury.

METHODS

Literature searches were conducted in MEDLINE (Ovid), Embase, Web of Science, and the Cochrane Central Register. The main outcome measures assessed were the proportion of eyes with best-corrected visual acuity (BCVA) ≥ 20/200 and the proportion retaining their original keratoprosthesis, both at the last recorded visit.

RESULTS

We identified 9 reports in which outcomes of Boston keratoprosthesis type I implantation after severe chemical injury could be determined, encompassing a total of 106 eyes of 100 patients. There were no randomized controlled studies. The median pre-operative BCVA was hand motion. Vision improved to ≥20/200 in 99/106 (93.4%) eyes after implantation. With a mean follow-up of 24.99 ± 14 months, 68/106 (64.1%) eyes retained BCVA ≥ 20/200 at the last examination. Therefore, 68/99 (68.7%) of those who improved to > 20/200 maintained at least this acuity. The originally implanted device was retained in 88/99 (88.9%) recipients for whom retention was reported. The mean time to failure was 22.36 ± 17.2 months. Glaucomatous optic neuropathy was the most common cause for BCVA <20/200 in eyes that retained the keratoprosthesis (18/27, 66.7%)..

CONCLUSIONS

Implantation of a Boston keratoprosthesis type I in eyes with corneal blindness after severe chemical ocular injury leads to functional vision in the majority of recipients. Evidence was limited by variability in outcome reporting and an absence of controlled studies..

Chemical Burns of the Eye: The Role of Retinal Injury and New Therapeutic Possibilities

PURPOSE

To propose a new treatment paradigm for chemical burns to the eye - in the acute and chronic phases.

METHODS

Recent laboratory and clinical data on the biology and treatment of chemical burns are analyzed.

RESULTS

Corneal blindness from chemical burns can now be successfully treated with a keratoprosthesis, on immediate and intermediate bases. Long term outcomes, however, are hampered by early retinal damage causing glaucoma. New data suggest that rapid diffusion of inflammatory cytokines posteriorly (TNF-α, etc) can severely damage the ganglion cells. Prompt anti-TNF-α treatment is markedly neuroprotective. Long term profound reduction of the intraocular pressure is also vital.

CONCLUSION

A new regimen, in addition to standard treatment, for severe chemical burns is proposed. This involves tumor necrosis factor alpha (TNF-α) inhibition promptly after the accident (primarily for retinal neuroprotection), prophylactic maximal lowering of the intraocular pressure (starting immediately), and keratoprosthesis implantation in a later quiet state.

Boston Keratoprosthesis Type 1 in Chemical Burns

PURPOSE

To describe and further analyze the long-term results in visual acuity (VA), anatomical retention, and rate of complications from patients who underwent Boston keratoprosthesis (B-Kpro) type 1 after ocular chemical burns in the Dominican Republic.

METHODS

A retrospective review of 42 eyes (22 OD:20 OS) of 36 patients who underwent B-Kpro type 1 implantation after severe ocular burn at Hospital Elías Santana in Santo Domingo, Dominican Republic, between April 2006 and October 2014, were included.

RESULTS

Demographics, VA, anatomical retention, and the rates of postoperative complications and concurrent surgeries were evaluated.

CONCLUSIONS

The excellent anatomical retention rates and visual outcomes presented in this study support the remarkable capability of B-Kpro type 1 to restore functional VA in eyes with severe chemical injuries. However, strict control of the postoperative complications is necessary for long-term success. In conclusion, the use of a B-Kpro type 1 after severe chemical burn is a viable option in patients otherwise condemned to the high risk of failure associated with conventional corneal grafts.

Current and Upcoming Therapies for Ocular Surface Chemical Injuries

Chemical injuries frequently result in vision loss, disfigurement, and challenging ocular surface complications. Acute interventions are directed at decreasing the extent of the injury, suppressing inflammation, and promoting ocular surface re-epithelialization. Chronically, management involves controlling inflammation along with rehabilitation and reconstruction of the ocular surface. Future therapies aimed at inhibiting neovascularization and promoting ocular surface regeneration should provide more effective treatment options for the management of ocular chemical injuries.

Potential New Modes of Treatment of Neurotrophic Keratopathy

The cornea focuses external light onto the retina, a function for which it must be transparent and possess a smooth surface. Homeostasis of the corneal epithelium is regulated by various humoral factors present in the tear fluid and by neural factors derived from the trigeminal nerve. Neurotrophic keratopathy (NK) is characterized by corneal epithelial disorders that result from impairment of trigeminal nerve function and a consequent deficiency of neural factors. The ideal mode of treatment for this condition is the regeneration of damaged trigeminal nerve fibers, but such therapy is not currently available. In this review, we describe established and potential new treatments of NK. Our research demonstrated that a combination of the neurotransmitter substance P and insulin-like growth factor 1 (IGF-1) has a synergistic stimulatory effect on corneal epithelial migration in vitro and on corneal wound closure in vivo. Furthermore, we identified the minimal amino acid sequences of substance P and IGF-1 required for this synergistic action based on the assumption that the clinical application of peptides corresponding to these sequences would have fewer side effects compared with the full-length molecules. Combination of the substance P-derived peptide FGLM-amide and the IGF-1-derived peptide SSSR promoted corneal epithelial wound healing in patients with NK.Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01756456.

Boston Keratoprosthesis Outcomes in Severe Ocular Chemical Burns in Southern China: A Retrospective Study

INTRODUCTION

The objective of this study was to report clinical outcomes (functional and anatomic) of Boston keratoprosthesis (KPro) after severe chemical burns in Southern China.

METHODS

Nineteen patients (19 eyes) that sustained severe chemical injuries in Southern China were enrolled in this retrospective study in our hospital between May 2009 and June 2015. KPro implantation in these patients was performed by a single experienced surgeon (Jiaqi Chen). The parameters evaluated in this study included diagnosis, comorbidity, preoperative and postoperative visual acuity (VA), complications, KPro retention, histological and immunohistochemical results of retroprosthetic membrane (RPM) and mucous membrane over the optic cylinder.

RESULTS

The mean age of the patients was 42.7 ± 11.3 years (range 29-62 years). All patients were male. Of the 19 included eyes, nine had acid burns, and 10 had alkali burns. Ten patients had previously undergone failed penetrating keratoplasty. The mean follow-up time was 41.3 ± 5.5 months (range 36-56 months). Preoperatively, the VA of the patients ranged from hand movement to light perception. Postoperatively, 17 patients (89.4%) achieved at least 20/200 once, and 7 patients (36.8%) achieved at least 20/200 and maintained this acuity until the last follow-up. The initial KPro was retained in 14 (73.6%) eyes and successfully replaced in one eye. Postoperative complications included RPM in 10 eyes, glaucoma in 6 eyes, retinal detachment in 2 eyes, corneal melting in 5 eyes, ischemic optic neuropathy in 1 eye, and overgrowth of the mucous membrane over the optical cylinder in 2 eyes. The histological and immunohistochemical results of the RPM showed granulomatous disorders and mucous membrane over the optic cylinder of conjunctival origin.

CONCLUSION

KPro surgery can restore useful vision in patients suffering from severe chemical burns. However, postoperative VA declined with the development of complications, and ocular surface disorders caused by the chemical burns were associated with a greater incidence of KPro retention failure. The retention rate was comparable in patients using ipsilateral autologous corneal tissue with allograft corneal tissue.

FUNDING

Science and Technology Foundation of Guangdong Province of China, Grant Number 2014A020212714.

Long-Term Results of the Boston Keratoprosthesis for Unilateral Corneal Disease

PURPOSE

To report the results of unilateral implantation of a Boston keratoprosthesis (BKPro) in patients with good visual acuity in the fellow eye.

METHODS

A retrospective analysis of 37 eyes of 37 patients who underwent an optical BKPro and had a preoperative best-corrected visual acuity (BCVA) of 20/40 or better in the fellow eye at Wills Eye Hospital from September 2005 to November 2013 was performed. Patients were excluded if they had less than 1 year of postoperative follow-up.

RESULTS

The mean follow-up after BKPro implantation was 31.7 months (range, 12-78 months; SD, 21). Twenty-eight patients underwent a BKPro for failed penetrating keratoplasty, and 9 patients underwent a primary BKPro. The most common complications were elevated intraocular pressure and retroprosthetic membrane formation in 16 eyes (43%) each. The mean final BCVA (1.0 ± 0.8 logMAR; median, 1.0 logMAR) was statistically better than the mean preoperative BCVA (1.8 ± 0.2 logMAR; median, 1.8 logMAR) (P < 0.001). The probability of postoperative BCVA of 20/200 or better was 54.1% with an average 45.1 ± 4.7 (confidence interval: 35.9-54.3) months of follow-up. The probability of postoperative BCVA of 20/40 or better was 37.8% with an average 51.8 ± 4.9 (confidence interval: 42.0-61.5) months of follow-up.

CONCLUSIONS

Half of the patients in our study achieved the minimum visual acuity required for binocular functioning, whereas one-third of the patients achieved a BCVA somewhat similar to that of the contralateral eye. The complications were similar to those reported previously with good retention of the device. BKPro implantation is a reasonable option for patients with good vision in the fellow eye.

Boston type 1 keratoprosthesis for chemical and thermal injury

PURPOSE

To evaluate the outcome of the Boston type 1 keratoprosthesis (Kpro-1) in eyes with failed interventions for chemical and thermal injury.

METHODS

A retrospective review was performed of every eye with chemical or thermal injury that was treated with a Kpro-1 at a tertiary eye care center between January 1, 2008 and July 1, 2013. The main outcome measures were visual outcome, prosthesis retention, and postoperative complications.

RESULTS

Nine eyes met the inclusion criteria, including 7 eyes with alkali burns, 1 eye with an acid burn, and 1 eye with a thermal burn. After a mean follow-up of 40.7 months (range, 29-60 months), the median best-corrected visual acuity was 20/60 (range, 20/15 to no light perception). One eye was ≥20/20, 3 eyes were ≥20/40, and 6 eyes were ≥20/70. The initial Kpro-1 prosthesis was retained in 7 (77.7%) eyes and successfully replaced in the other 2 eyes. One or more serious complications occurred in 6 (66.7%) eyes. These included 2 cases of sterile corneal ulceration with prosthesis extrusion, 2 cases of microbial keratitis (1 bacterial and 1 fungal), 2 cases of bacterial endophthalmitis, and 2 cases of retinal detachments. These complications contributed to visual outcomes of hand motions in 2 eyes and no light perception in 1 eye.

CONCLUSIONS

The Boston Kpro-1 is associated with highly satisfactory visual outcomes and prosthesis retention in most cases of severe chemical or thermal injury. Serious complications are common and may compromise the final outcome.

Retinal detachments after Boston Keratoprosthesis: incidence, predisposing factors, and visual outcomes

PURPOSE

To determine the rates, predisposing factors, and visual outcomes of retinal detachment (RD) after Boston Keratoprosthesis (KPro) implantation.

METHODS

In this noncomparative, interventional case series, the medical records of 170 patients (205 eyes) who underwent Boston type 1 and type 2 KPro implantation at the Massachusetts Eye and Ear Infirmary between April 1993 and June 2009 were retrospectively reviewed. Incidence and annual rates of RD were calculated, and the roles of possible predictive factors for RD after KPro were investigated. Main outcome measures were rates of and risk factors for RD, visual acuity after RD, and surgical outcomes after repair.

RESULTS

Sterile vitritis and autoimmune systemic disease significantly predisposed patients to RD after KPro placement. Of patients who developed RD after implantation, 50% progressed to visual acuity of no light perception despite surgical repair.

CONCLUSIONS

Inflammation plays a major role in RD development after KPro implantation. Patients with predisposing factors should be advised of the high rates of RD and comanaged with a vitreoretinal specialist.

Boston keratoprosthesis type 1 for herpes simplex and herpes zoster keratopathy

PURPOSE

The aim of this study was to evaluate and compare the outcomes of Boston keratoprosthesis type 1 (Kpro-1) in eyes with herpes simplex virus (HSV) and herpes zoster virus (HZV) keratopathy.

METHODS

A retrospective review was performed of the medical records of every patient treated with a Boston Kpro-1 at the University of Iowa Hospitals and Clinics between January 1, 2008 and July 1, 2012. Eyes with visual loss due to HSV or HZV keratopathy were included in the statistical analysis. The main outcome measures were graft retention, postoperative complications, and visual outcome.

RESULTS

Nine eyes met the inclusion criteria, including 5 eyes in the HSV group and 4 eyes in the HZV group. The graft retention rate was 100% in the HSV group after a mean follow-up of 48.4 months, compared with 25% in the HZV group after 50.5 months (P = 0.048). There were 3 cases of microbial keratitis, including 2 eyes that also developed endophthalmitis, in the HZV group, compared with no cases in the HSV group (P = 0.048). There was significantly better best-corrected visual acuity at the most recent examination in the HSV group than in the HZV group (P = 0.019). All 5 HSV eyes had improved best-corrected visual acuity compared with preoperative acuity, whereas only 1 HZV eye experienced a similar result (P = 0.048).

CONCLUSIONS

Kpro-1 is associated with an excellent prognosis for graft retention, acceptably low prevalence of sight-threatening complications, and highly satisfactory visual improvement in eyes with HSV keratopathy, but not in eyes with HZV keratopathy.

Artificial corneas versus donor corneas for repeat corneal transplants

BACKGROUND

Individuals who have failed one or more full thickness penetrating keratoplasties (PKs) may be offered repeat corneal surgery using an artificial or donor cornea. An artificial or prosthetic cornea is known as a keratoprosthesis. Both donor and artificial corneal transplantations involve removal of the diseased and opaque recipient cornea (or the previously failed cornea) and replacement with another donor or prosthetic cornea.

OBJECTIVES

To assess the effectiveness of artificial versus donor corneas in individuals who have had one or more failed donor corneal transplantations.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2013, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2013), EMBASE (January 1980 to November 2013), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to November 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 27 November 2013.

SELECTION CRITERIA

Two review authors independently assessed reports from the electronic searches to identify randomized controlled trials (RCTs) or controlled clinical trials (CCTs). We resolved discrepancies by discussion or consultation with a third review author.

DATA COLLECTION AND ANALYSIS

For discussion purposes, we assessed findings from observational cohort studies and non-comparative case series. No data synthesis was performed.

MAIN RESULTS

We did not identify any RCTs or CCTs comparing artificial corneas with donor corneas for repeat corneal transplantations.

AUTHORS' CONCLUSIONS

The optimal management for those individuals who have failed a conventional corneal transplantation is not known. Currently, in some centers, artificial corneal devices routinely are recommended after just one graft failure, and in others, not until after multiple graft failures, or not at all. To date, there have been no controlled trials comparing the visual outcomes and complications of artificial corneal devices (particularly the Boston type 1 keratoprosthesis which is the most commonly implanted artificial corneal device) with repeat donor corneal transplantation, in order to guide surgeons and their patients. It is apparent that such a trial is needed and would offer significant benefit to an ever-increasing pool of people with visual disability due to corneal opacification, most of whom are still in productive stages of their lives.

Keratoconus: tissue engineering and biomaterials

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.

Successful Müller muscle-conjunctiva resection in patients with Boston keratoprosthesis type I

PURPOSE

To present a case series of patients with Boston keratoprosthesis type I (KPro) who have had successful ptosis repair with Müller muscle-conjunctiva resection (MMCR).

METHODS

Patients with KPros managed with MMCR for ptosis were identified. Records were examined to obtain preoperative and postoperative visual acuity, KPro viability, and eyelid measurements including margin-to-reflex distance 1 (MRD1), levator function, and lagophthalmos.

RESULTS

Seven eyes of 6 patients with KPros and ptosis treated with MMCR were identified. Four eyes underwent a lower lid tarsal strip procedure concurrently with the MMCR to minimize the risk of exposure to the graft postoperatively. The average time between KPro surgery and ptosis surgery was 29.1 months (range, 4-79 months). Preoperatively, the average MRD1 was -2.4 mm and the average levator function was 11.3 mm. Postoperatively, all eyelids were elevated and the average MRD1 was 0.9 mm. One eye had 0.5 mm of lagophthalmos noted whereas all other eyes had no lagophthalmos. The average follow-up time was 25.9 months (range, 13-41 months). All 7 eyes maintained a viable KPro without any compromise to the conjunctiva or donor corneal tissue.

CONCLUSIONS

This retrospective case series describes 7 eyes with KPros that underwent successful MMCR without compromise to the integrity of the KPro. Because these patients are at high risk for potential complications, we recommend careful patient selection, a goal of undercorrection, and consideration of supplemental procedures to the lower eyelids to minimize complications to the KPro.

The ocular surface chemical burns

Ocular chemical burns are common and serious ocular emergencies that require immediate and intensive evaluation and care. The victims of such incidents are usually young, and therefore loss of vision and disfigurement could dramatically affect their lives. The clinical course can be divided into immediate, acute, early, and late reparative phases. The degree of limbal, corneal, and conjunctival involvement at the time of injury is critically associated with prognosis. The treatment starts with simple but vision saving steps and is continued with complicated surgical procedures later in the course of the disease. The goal of treatment is to restore the normal ocular surface anatomy and function. Limbal stem cell transplantation, amniotic membrane transplantation, and ultimately keratoprosthesis may be indicated depending on the patients' needs.

Boston type 1 keratoprosthesis outcomes in ocular burns

PURPOSE

To report the outcomes of Boston type I keratoprosthesis (BKPro) in the management of ocular burn injuries.

METHODS

This was a prospective study including all cases of BKPro implantation for ocular burns at the External Diseases and Cornea Service of the Federal University of São Paulo, between February 2008 and February 2010. Ten patients (10 eyes) were enrolled. Procedures performed to manage ocular injury were identified, and data were collected regarding patients' ocular history, surgical procedure(s) performed, and postoperative outcomes, including visual acuity, retention, complications and required surgical procedures.

RESULTS

A total of 11 Type 1 BKPro were implanted in 10 eyes of 10 patients. The mean follow-up period was 25.7 ± 10.8 months. Preoperative best-corrected visual acuity (BCVA) ranged from count fingers to light perception. Postoperative BCVA was better than 20/200 in 90% of the patients and better than 20/60 in 60% of the patients. The overall BKPro retention rate was 90%. The most common complications were retroprosthetic membrane formation (50%) and persistent corneal epithelial defect evolving to corneal melting (40%). Patients who underwent ocular surface procedures such as limbal transplantation prior to BKPRo implantation had a lower incidence of corneal melting/thinning (p = 0.07), although this was not statistically significant.

CONCLUSION

The anatomical and functional results identified in this study support the use of BKPro in managing bilateral limbal stem cell deficiency secondary to ocular burns.

Outcomes of the Boston keratoprosthesis in jordan

Purpose:

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.

Results:

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.

Conclusion:

Boston Kpro offers a reasonably safe and effective solution for patients with corneal blindness in whom the prognosis for natural corneal grafting is poor.

Short-term outcome of Boston Type 1 keratoprosthesis for bilateral limbal stem cell deficiency

This study reports the short-term functional and anatomical outcome of Boston Type 1 keratoprosthesis (Boston Kpro) implantation for bilateral limbal stem cell deficiency (LCSD). Retrospective analysis was done on eight eyes of eight patients who underwent Boston Kpro implantation between July 2009 and October 2009. The best corrected visual acuity (BCVA) and slit-lamp biomicroscopy findings were assessed at 1, 3 and 6 months postoperatively. All eight eyes retained the prosthesis. BCVA of 20/40 or better was achieved in 8, 6, and 5 eyes at 1, 3, and 6 months, respectively, postoperatively. One patient each developed epithelial defect, sterile stromal melt and fungal keratitis in the late postoperative period associated with antecedent loss of the soft contact lens from the eye. Boston Kpro has good short-term visual and anatomical outcome in patients with bilateral LSCD, provided compliance with postoperative care can be ensured.

Glaucoma in eyes with severe chemical burn, before and after keratoprosthesis

PURPOSE

The purpose of this study was to evaluate the incidence of glaucoma in eyes with severe chemical burn, before and after keratoprosthesis.

METHODS

A retrospective chart review of 28 eyes of 23 patients with severe ocular chemical burns who had undergone Boston Keratoprosthesis (BKPro) surgery at the Massachusetts Eye and Ear Infirmary, between 1990 and 2010. The incidence and severity of the outcome of glaucoma, preoperatively and postoperatively, were reviewed. Related issues, such as type of chemical burn; visual acuity (VA); device retention rate; number and nature of previous, concomitant, and subsequent procedures; and incidence of other postoperative complications, were reviewed for a median follow-up time of 57 months.

RESULTS

The number of eyes with a preoperative history or signs of glaucoma was 21, 9 of which had glaucoma progression after BKPro implantation. In addition, 2 more eyes developed glaucoma postoperatively. Preoperative vision was counting fingers or worse in all eyes. Best-corrected postoperative VA ranged from no light perception to 20/20. Seventeen eyes (61%) achieved 20/60 or better VA at some point during their follow-up, but only 9 (32%) maintained 20/60 at the last follow-up. Of the 28 eyes, 6 had the BKPro replaced once and 1 had it replaced twice. Superimposed, 8 of the most severely burned patients developed retinal detachment postoperatively.

CONCLUSIONS

Glaucoma is very common in eyes with severe chemical burns. A keratoprosthesis can rehabilitate vision, but postoperative glaucoma can be difficult to manage.

Boston type 1 keratoprosthesis: the New York Eye and Ear experience

PURPOSE

The Boston keratoprosthesis has had variable success rates in the past. However, significant modifications to design and management have recently led to successful outcomes. This study was undertaken to evaluate the outcomes of the Boston type 1 keratoprosthesis at our institution.

METHODS

A retrospective chart review was performed of all Boston type 1 keratoprosthesis procedures conducted at a single practice at the New York Eye and Ear Infirmary from December 2006 to August 2010. Outcome measures included visual acuity, retention rates, and complications.

RESULTS

In all, 58 eyes of 51 patients who received a Boston type 1 keratoprosthesis were included. The most common indication for the keratoprosthesis was failed penetrating keratoplasty (PK) (81.0%; mean 2.4±1.3 PKs per eye). Glaucoma was the most common comorbidity (75.9%). Pre-operative best corrected visual acuity (BCVA) was <20/400 in 87.9% of eyes. At last follow-up, 43.1% of eyes had a BCVA of 20/200. Retention rate was 87.9% over an average follow-up of 21.5±11.4 months (median 22 months, range 3-47 months). Complications increased with time, with 65.5% of eyes experiencing at least one event by 6 months and 75.9% by 1 year. The most common post-operative complication was retroprosthetic membrane formation (50.0%).

CONCLUSIONS

The Boston type 1 keratoprosthesis provides visual recovery for eyes with multiple PK failures or with poor prognosis for primary PK, showing excellent retention rates. However, there is a trend towards a decline in visual acuity with time and the development of late complications, highlighting a need for longer-term studies.