Boston Keratoprosthesis Outcomes and Complications

Visual outcomes of primary keratoprosthesis implantation in transplant-naïve eyes

PURPOSE

Primary keratoprosthesis (Kpro) implantation may be indicated in eyes that have an expected poor prognosis following initial penetrating keratoplasty, such as eyes with limbal stem cell deficiency (LSCD). We compare visual outcomes of eyes undergoing primary Kpro to eyes that had a secondary Kpro following penetrating keratoplasty.

METHODS

Retrospective review of all patients who had Kpro implantation at a tertiary academic medical center from 2005-2020. Among those, eyes that had undergone primary Kpro implantation without a history of prior corneal transplantation were also identified.

RESULTS

Eighty-four eyes of 77 patients that had undergone Kpro implantation were identified. Of those 84, 12 eyes (21.4%) of 12 patients were receiving primary Kpro since they were corneal transplant-naïve. Among individuals undergoing primary Kpro implantation compared to secondary Kpro implantation, the most common underlying diagnoses were limbal stem cell deficiency (41.7% vs 10.0%, p = 0.01304), corneal scarring not otherwise specified (25.0% vs 2.86%, p = 0.02077), and neurotrophic cornea (16.7% vs 2.86%, p = 0.1002). Eyes undergoing primary Kpro implantation had similar mean visual acuity to eyes undergoing secondary Kpro preoperatively (20/2118 vs 20/3786, p = 0.271), 3 months postoperatively (20/264 vs 20/758, p = 0.174), and at final follow up (average 3.06 years, 20/907 vs 20/3446, p = 0.070). Average follow-up time and rates of glaucoma, endophthalmitis, retroprosthetic membrane, and retinal detachment did not significantly differ between groups (all p > 0.05). All eyes that progressed to no light perception (n = 13) had undergone secondary Kpro implantation.

CONCLUSIONS

Visual acuity outcomes were similar between primary Kpro implantation and secondary Kpro implantation. Eyes that underwent primary Kpro implantation trended toward better postoperative VA at final follow-up than secondary Kpro eyes.

Causes of Corneal Melt After the Boston Keratoprosthesis Type I: The Chinese People's Liberation Army General Hospital Experience

PURPOSE

The purpose of this study was to evaluate the long-term incidence, risk factors, and the management of corneal melt following Boston type I keratoprosthesis (B-KPro I) implantation.

METHODS

This is a retrospective observational case series. Data were collected regarding demographics, preoperative characteristics, incidence, and outcomes of corneal melt in 102 patients who underwent B-KPro I in the Chinese PLA General Hospital between 2011 and 2018, with a follow-up period ranging from 4 to 11 years.

RESULTS

Chemical burn was the most common indication for B-KPro I (n = 56; 53.8%), followed by ocular trauma (n = 26; 25.0%). During the follow-up period (107 ± 25.7 months), corneal melt occurred in 60 cases among 37 eyes (35.6%), with an incidence of 20.2% at 1 year after surgery. Fourteen cases presented with recurrent corneal melt. Patients with multiple corneal allograft failures had a higher risk of corneal melt. Thermal burns, compared with alkali burns, significantly elevated the odds ratio (OR) of corneal melt (OR, 5.11; 95% confidence interval, 1.05-24.86; P = 0.043).

CONCLUSIONS

Corneal melt significantly reduced the retention time of KPro ( P < 0.01), and its coexistence with other complications further shortened the retention time. A specific pattern of corneal melt occurrence was identified, with a peak incidence at 1 year postoperatively. Our findings suggest variations in the risk of corneal melt among different indications, with thermal burns carrying the highest OR. Moreover, each previous failed keratoplasty doubled the risk of corneal melt after B-KPro I.

Retrocorneal fibrous membrane after phacoemulsification in an eye with pseudoexfoliative glaucoma

OBJECTIVE

To report a case of a retrocorneal fibrous membrane and corneal decompensation following uncomplicated phacoemulsification in an eye with pseudoexfoliative glaucoma.

METHOD

Case report and literature review.

RESULTS

A monocular 83-year-old female developed corneal decompensation 1 year after uncomplicated cataract extraction via phacoemulsification. She had a history of pseudoexfoliative glaucoma and had undergone 3 rounds of selective laser trabeculoplasty in the same eye 3 years prior. Given the resulting corneal edema, the patient underwent Descemet's membrane endothelial keratoplasty, at which time a retrocorneal fibrous membrane was identified. Peeling of the membrane was surgically challenging and resulted in an intraocular hemorrhage intraoperatively and a small iridodialysis because the membrane had extended over the angle and iris. Postoperatively, the cornea cleared well, and vision improved significantly. However, vision was ultimately limited by macular pathology. Pathologic examination demonstrated Descemet's membrane with an attached fibrocellular membrane. Immunostaining for smooth muscle actin was positive within the membrane compatible with a retrocorneal membrane. We also present a review of the literature on modern causes of retrocorneal fibrous membranes.

CONCLUSIONS

Retrocorneal fibrous membranes are encountered most commonly following corneal transplantation and may be surgically challenging to remove. We present the first case of a pathologically proven retrocorneal fibrous membrane following uncomplicated cataract surgery via phacoemulsification and selective laser trabeculoplasty.

Use of PROSE for long-term ocular surface support in patients with a permanent keratoprosthesis

Purpose

To describe the long-term outcome of the use of a specialized scleral lens known as a prosthetic replacement of the ocular surface ecosystem (PROSE) device to support the ocular surface in patients with a Boston Keratoprosthesis (KPro) Type I. All patients in this series were unable to pursue continuous wear of a bandage soft contact lens (BSCL) - a critical aspect of post KPro implantation management intended to protect the corneal carrier tissue from desiccation and stromal melting.

Observations

Four eyes of four patients with a Boston KPro Type I were included. All four had failed BSCL wear and were instead treated with PROSE device wear. All four patients had underlying diagnoses associated with a diseased ocular surface (Stevens-Johnson Syndrome [one patient], prior failed penetrating keratoplasty associated with herpes zoster-related neurotrophic keratopathy [one patient], and prior failed penetrating keratoplasty associated with severe dry eye disease [two patients]). Causes of failure of BSCL wear included poor retention, discomfort, and poor vision. PROSE device wear was initiated on average seven and a half (range four to 14) months post-KPro implantation. The wear schedule varied and ranged from waking-hour wear only to 24-h wear. The average duration of device wear was 59.3 (range 28-103) months. Two patients exhibited persistent corneal epithelial defect formation with waking-hour wear, which resolved within 10 days with 24-h device wear. All patients exhibited improvement in vision with PROSE compared to baseline, averaging six and a half (range six to eight) lines of improvement in Snellen acuity, and all patients reported increased comfort. There was no incidence of microbial keratitis, KPro device instability, or other complication throughout the duration of device wear.

Conclusions and Importance

This report offers a novel alternate approach to long-term support of the ocular surface in patients with a Boston KPro who fail standard continuous BSCL wear.

Successful use of conjunctival flaps to prolong survival of type I keratoprosthesis in severe bilateral chemical burns: two case reports

INTRODUCTION

This report describes the use of conjunctival flaps to enable the survival of type I keratoprosthesis (KPro) in two cases of bilateral severe total limbal stem cell deficiency (LSCD) following chemical burns.

PRESENTATION OF CASE

Two patients had a history of bilateral chemical injury with lime. On examination, the presenting vision was light perception to hand motions and both cases had conjunctivalized ocular surfaces with symblepharon. A modified technique of type I keratoprosthesis was used, where the conjunctivalized corneal pannus was dissected and lifted off as an inferior fornix-based conjunctival flap. This was followed by a standard surgical technique of type I KPro. The flap was then secured over the device and optical opening was made two weeks later. Both the patients had stable ocular surfaces with visual acuity of 20/20 at 2-7 years of follow-up.

DISCUSSION

In patients with total LSCD with adnexal involvement, type I KPro has unsatisfactory long-term survival because of the risk of repeated epithelial breakdowns and stromal ulceration. With the innovative approach described in this report, type I KPro can be successfully used for sustainable visual improvement in the presence of severe ocular surface disease and symblepharon.

CONCLUSION

Conjunctival flaps can be used along with type I KPros to improve long-term survival and give sustainable visual outcomes in cases of bilateral corneal blindness due to advanced ocular surface damage.

Arrested Phase Separation Enables High-Performance Keratoprostheses

Corneal transplantation is impeded by donor shortages, immune rejection, and ethical reservations. Pre-made cornea prostheses (keratoprostheses) offer a proven option to alleviate these issues. Ideal keratoprostheses must possess optical clarity and mechanical robustness, but also high permeability, processability, and recyclability. Here, it is shown that rationally controlling the extent of arrested phase separation can lead to optimized multiscale structure that reconciles permeability and transparency, a previously conflicting goal by common pore-forming strategies. The process is simply accomplished by hydrothermally treating a dense and transparent hydrophobic association hydrogel. The examination of multiscale structure evolution during hydrothermal treatment reveals that the phase separation with upper miscibility gap evolves to confer time-dependent pore growth due to slow dynamics of polymer-rich phase which is close to vitrification. Such a process can render a combination of multiple desired properties that equal or surpass those of the state-of-the-art keratoprostheses. In vivo tests confirm that the keratoprosthesis can effectively repair corneal perforation and restore a transparent cornea with treatment outcomes akin to that of allo-keratoplasty. The keratoprosthesis is easy to access and convenient to carry, and thus would be an effective temporary substitute for a corneal allograft in emergency conditions.

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.

Ultra-wide field imaging to assess the optic nerve and retina in Boston type I and II keratoprosthesis patients

Background

The ability to view the posterior segment in keratoprosthesis (Kpro) implanted patients is limited. The purpose of this retrospective, observational study was to investigate the use of ultra-wide field (UWF) scanning laser ophthalmoscopy imaging and its utility for serial evaluation of the retina and optic nerve in patients with either a Boston type I or II Kpro.

Methods

A retrospective chart review was performed for patients with a Boston type I or II Kpro seen at The Ohio State University Wexner Medical Center. Images were graded for quality by two masked observers on a defined four-point scale (“Poor”, “Fair”, “Good”, or “Very good”) and assessed for visible posterior segment anatomy. Interobserver agreement was described using the Kappa statistic coefficient (κ) with 95% confidence intervals.

Results

A total of 19 eyes from 17 patients were included in this study. Eighteen eyes had a type I Kpro, while one eye had a type II Kpro. UWF imaging from 41 patient visits were reviewed by two observers. Interobserver agreement between the two graders was fair for image quality (κ = 0.36), moderate for visibility of the macula with discernible details (κ = 0.59), moderate for visibility of the anterior retina with discernable details (κ = 0.60), and perfect agreement for visibility of the optic nerve with discernible details (κ = 1.0). In 6 eyes, UWF imaging was performed longitudinally (range 3–9 individual visits), allowing for long-term follow-up (range 3–46 months) of posterior segment clinical pathology.

Conclusions

UWF imaging provides adequate and reliable visualization of the posterior segment in Kpro implanted patients. This imaging modality allowed for noninvasive longitudinal monitoring of retinal and optic nerve disease in this selected patient population.

[Tonometry: Review and Perspectives]

Reliable and repeated IOP measurement are essential in the diagnosis and treatment of glaucoma. In this first part of this review, besides the physiological basics, contact tonometry will be presented, which is both the first instrumental method with the indentation tonometers and the gold standard with the Goldmann applanation tonometer. Both methods and subsequently developments will be discussed.

Tonometrie: Rückblick und Ausblick (Teil 1)

Der intraokulare Druck (IOD) ist ein wichtiger physikalischer Parameter der Physiologie des Auges. Ein erhöhter IOD wurde früh als Ätiologie für Augenerkrankungen vermutet. In diesem 1. Teil des Beitrags wird neben den physiologischen Grundlagen die Kontakttonometrie vorgestellt, die sowohl die erste instrumentelle Methode mit den Indentationstonometern als auch den Goldstandard mit dem Goldmann-Applanationstonometer darstellt.

In Situ-Forming Collagen-Hyaluronate Semi-Interpenetrating Network Hydrogel Enhances Corneal Defect Repair

Purpose

Millions worldwide suffer vision impairment or blindness from corneal injury, and there remains an urgent need for a more effective and accessible way to treat corneal defects. We have designed and characterized an in situ-forming semi-interpenetrating polymer network (SIPN) hydrogel using biomaterials widely used in ophthalmology and medicine.

Methods

The SIPN was formed by cross-linking collagen type I with bifunctional polyethylene glycol using N-hydroxysuccinimide ester chemistry in the presence of linear hyaluronic acid (HA). Gelation time and the mechanical, optical, swelling, and degradation properties of the SIPN were assessed. Cytocompatibility with human corneal epithelial cells and corneal stromal stem cells (CSSCs) was determined in vitro, as was the spatial distribution of encapsulated CSSCs within the SIPN. In vivo wound healing was evaluated by multimodal imaging in an anterior lamellar keratectomy injury model in rabbits, followed by immunohistochemical analysis of treated and untreated tissues.

Results

The collagen-hyaluronate SIPN formed in situ without an external energy source and demonstrated mechanical and optical properties similar to the cornea. It was biocompatible with human corneal cells, enhancing CSSC viability when compared with collagen gel controls and preventing encapsulated CSSC sedimentation. In vivo application of the SIPN significantly reduced stromal defect size compared with controls after 7 days and promoted multilayered epithelial regeneration.

Conclusions

This in situ-forming SIPN hydrogel may be a promising alternative to keratoplasty and represents a step toward expanding treatment options for patients suffering from corneal injury.

Translational Relevance

We detail the synthesis and initial characterization of an SIPN hydrogel as a potential alternative to lamellar keratoplasty and a tunable platform for further development in corneal tissue engineering and therapeutic cell delivery.

Electrical Signal Initiates Kinetic Assembly of Collagen to Construct Optically Transparent and Geometry Customized Artificial Cornea Substitutes

Corneal transplantation is an effective treatment for reconstructing injured corneas but is very limited due to insufficient donors, which has led to a growing demand for development of artificial corneal substitutes (ACSs). Collagen is a potential building block for ACS fabrication, whereas technically there are limited capabilities to control the collagen assembly for creating highly transparent collagen ACSs. Here, we report an electro-assembly technique to kinetically control collagen assembly on the nanoscale that allows the yielding collagen ACSs with structure determined superior optics. Structurally, the kinetically electro-assembled collagen (KEA-Col) is composed of partially aligned microfibrils (∼10 nm in diameter) with compacted lamellar organization. Optical analysis reveals that such microstructure is directly responsible for its optimal light transmittance by reducing light scattering. Moreover, this method allows the creation of complex three-dimensional geometries and thus is convenient to customize collagen ACSs with specific curvatures to meet refractive power requirements. Available properties (e.g., optics and mechanics) of cross-linked KEA-Cols were studied to meet the clinical requirement as ACSs, and in vitro tests further proved their beneficial characteristics of cell growth and migration. An in vivo study established a rabbit lamellar keratectomy corneal wound model and demonstrated the customized collagen ACSs can adapt to the defective cornea and support epithelial healing as well as stroma integration and reconstruction with lower immunoreaction compared with commercial xenografts, which suggests its promising application prospects. More broadly, this work illustrates the potential for enlisting electrical signals to mediate collagen's assembly and microstructure organization for specific structural functionalization for regenerative medicine.

Retroprosthetic Membrane Formation in Boston Keratoprosthesis Type 1: Incidence, Predisposing Factors, Complications, and Treatment

PURPOSE

The purpose of this study was to evaluate the incidence, rate of formation, and risk factors of retroprosthetic membrane (RPM) after Boston type 1 keratoprosthesis (BKPro) as well as identify secondary complications linked to its formation and describe its treatment.

METHODS

This was a retrospective cohort study. One hundred thirty-three eyes of 115 patients who underwent BKPro implantation at the Centre Hospitalier de l'Université de Montréal from 2008 to 2017 were included with at least 1-year follow-up. Charts were reviewed, and data were collected, including incidence of RPM formation, preoperative and intraoperative risk factors, postoperative complications, and treatment modalities.

RESULTS

The mean follow-up was 5.5 years, and 39% (n = 52) of eyes developed RPM. No etiologies were found to be significantly associated with RPM development. Simultaneous lensectomy and simultaneous intraocular lens extraction were respectively positively and negatively correlated with RPM development [odds ratio (OR): 0.3590, 95% CI: 0.1629-0.7570, P = 0.0097; OR = 2.646, 95% CI: 1.273-5.585, P = 0.0086, respectively]. As for postoperative complications, the strongest correlation was between RPM and retinal detachment (OR = 6.16, 95% CI: 2.14-16.14; P = 0.0004). RPM development was also positively associated with the development of hypotony and corneal melt. Nd:YAG membranectomy was the most common treatment, performed in 83% of eyes with RPM (n = 24), with 58% resolution.

CONCLUSIONS

More than one third of patients who undergo BKPro will develop RPM, requiring close monitoring for retinal detachment. Simultaneous intraocular lens extraction seems protective, whereas simultaneous lens extraction increases the rate of RPM formation significantly. Nd:YAG membranectomy can be used as an initial noninvasive approach.

Extracellular Vesicles in Corneal Fibrosis/Scarring

Communication between cells and the microenvironment is a complex, yet crucial, element in the development and progression of varied physiological and pathological processes. Accumulating evidence in different disease models highlights roles of extracellular vesicles (EVs), either in modulating cell signaling paracrine mechanism(s) or harnessing their therapeutic moiety. Of interest, the human cornea functions as a refractive and transparent barrier that protects the intraocular elements from the external environment. Corneal trauma at the ocular surface may lead to diminished corneal clarity and detrimental effects on visual acuity. The aberrant activation of corneal stromal cells, which leads to myofibroblast differentiation and a disorganized extracellular matrix is a central biological process that may result in corneal fibrosis/scarring. In recent years, understanding the pathological and therapeutic EV mechanism(s) of action in the context of corneal biology has been a topic of increasing interest. In this review, we describe the clinical relevance of corneal fibrosis/scarring and how corneal stromal cells contribute to wound repair and their generation of the stromal haze. Furthermore, we will delve into EV characterization, their subtypes, and the pathological and therapeutic roles they play in corneal scarring/fibrosis.

Long-term results of Boston keratoprosthesis surgery in Polish patients

Introduction

To evaluate the long-term (10 year) outcomes of Boston type 1 keratoprosthesis (BKPro; Massachusetts Eye and Ear Infirmary, Boston, MA) surgery performed in 6 Polish patients.

Materials and Methods

6 eyes of 6 patients (1 female and 5 males; mean age 49,5±6,34 years) were qualified for the surgery. Indications for BKPro surgery in the study group included: corneal graft failure (3 patients), chemical ocular burns (2 patients), and post-herpetic keratitis vascularized leucoma (1 patient). Visual acuity, slit-lamp examination with ocular surface assessment, anterior segment optical coherence tomography (AS OCT), fundoscopy, and intraocular digital pressure measurement were performed at each visit.

Results

Retention of keratoprosthesis was achieved in all patients during the follow-up period. At last recorded visits VA≥0,2 was observed in 3 patients, LP in one patient and NLP in 2 patients. The complications which occurred in our case series were: glaucoma (4 patients preoperatively, 6 patients postoperatively), retroprosthetic membrane formation (1 patient), epimacular membrane formation (2 patients) and severe Meibomian Gland Dysfunction (3 patients). OCT analysis allowed imaging of anterior iris synechiae, AGV tube, protrusion of the BKPro and retroprosthetic membrane not visible on the slit lamp examination.

Conclusions

BKPro surgery should be considered as a surgery of choice in patients who have high risk of PK failure. OCT plays a role in anterior eye segment monitoring and detection of complications not visible on the slit lamp examination in the follow up period. Implementing the dry eye disease treatment should be recommended in all patients undergoing BKPro surgery.

Assessment of the Role and Timing of Glaucoma Surgery in Boston Keratoprosthesis Type 1 Patients

PURPOSE

To determine the role and optimal timing of glaucoma surgery in relation to Boston keratoprosthesis type 1 (KPro) implantation.

DESIGN

Retrospective, comparative, nonrandomized clinical study.

METHODS

Single-center study of a total of 100 eyes (100 patients) implanted with a KPro between 2008 and 2017, and diagnosed with glaucoma before or after KPro. Patients were separated into 2 groups: those with preexisting glaucoma and those who developed de novo glaucoma after KPro. Groups were then divided based on whether patients were medically or surgically managed. Glaucoma surgery included glaucoma drainage device (GDD) implantation, trabeculectomy, and cyclophotocoagulation (CPC). Primary outcomes included best-corrected visual acuity (BCVA), glaucoma progression, and complications. Differences in outcomes were compared using parametric and nonparametric tests, as well as log-rank test to compare time-to-outcome events.

RESULTS

Among 72 eyes with preexisting glaucoma, 27 (38%) had glaucoma surgery before KPro (18 GDD), whereas 45 (62%) were medically managed only. Among the latter, 19 (42%) needed glaucoma surgery post-KPro (16 GDD). Among 28 eyes with de novo glaucoma, 12 (43%) had glaucoma surgery post-KPro (9 GDD). For eyes with preexisting glaucoma, glaucoma progression was greater with glaucoma surgery performed post-KPro (100%) compared with pre-KPro (74%, P = .016) and to medical management (54%, P = .002). No increase in complications were observed with glaucoma surgery compared to medications only (P > .05), whereas fewer eyes maintained a BCVA of 20/200 or better over time with medical management (P = .013). Eyes with de novo glaucoma had similar progression, BCVA, and complications between medical and surgical care (P > .05).

CONCLUSIONS

Glaucoma surgery should be performed before or at the same time as KPro implantation in eyes with preexisting glaucoma. Complication rates are not increased when glaucoma surgery is performed in KPro eyes with either preexisting or de novo glaucoma. To ensure optimal glaucoma control, glaucoma surgery should be performed as early as possible in KPro eyes with good visual potential.

Challenges of Glaucoma Management in Patients with Type I Boston Keratoprosthesis

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

Long-term Outcomes of Boston Type I Keratoprosthesis, and Efficacy of Amphotericin B and Povidone-Iodine in Infection Prophylaxis

PURPOSE

To evaluate the long-term outcomes, anatomic retention, and complications of Boston type I keratoprosthesis (KPro).

DESIGN

Retrospective, interventional case series METHODS: A retrospective chart review of implantations performed January 2008-December 2017 was conducted. Risk factors for anatomical retention and functional success were analyzed. The incidences of infections with and without antimicrobial medications were compared.

RESULTS

Twenty-seven eyes of 26 patients were recruited. The most common indication for KPro surgery was failed penetrating keratoplasties (22 eyes, 81.5%). All patients had preoperative best-corrected visual acuity (BCVA) worse than 3/60. Over the mean follow-up of 83.4 ± 28.4 months, 15 eyes (55.6%) demonstrated improved BCVA. The anatomical retention rate was 88.9%, and the functional success rate was 44.4% (retained KPro with BCVA ≥ 3/60). Eyes with ocular surface disease (OSD) had significantly more complications than those without OSD. The most common complications were retroprosthetic membrane formation (15 eyes, 55.6%) and infection (13 eyes, 48.1%). Infectious keratitis was primarily caused by gram-positive bacteria, whereas endophthalmitis was chiefly caused by fungal infection. The infection incidence was significantly lower in eyes using topical 0.1% amphotericin B and 5% povidone iodine (P = .008 and .021, respectively).

CONCLUSIONS

With its good retention rate and visual outcomes, Boston type I KPro could be an alternative treatment for patients with conventional penetrating keratoplasty failure, especially with appropriate patient selection and complication prevention. Standard prophylactic antibiotics with the addition of topical 0.1% amphotericin B and 5% povidone iodine might be optional effective regimens for infection prevention, especially in tropical countries.

Artificial Cornea: Past, Current, and Future Directions

Corneal diseases are a leading cause of blindness with an estimated 10 million patients diagnosed with bilateral corneal blindness worldwide. Corneal transplantation is highly successful in low-risk patients with corneal blindness but often fails those with high-risk indications such as recurrent or chronic inflammatory disorders, history of glaucoma and herpetic infections, and those with neovascularisation of the host bed. Moreover, the need for donor corneas greatly exceeds the supply, especially in disadvantaged countries. Therefore, artificial and bio-mimetic corneas have been investigated for patients with indications that result in keratoplasty failure. Two long-lasting keratoprostheses with different indications, the Boston type-1 keratoprostheses and osteo-odonto-keratoprostheses have been adapted to minimise complications that have arisen over time. However, both utilise either autologous tissue or an allograft cornea to increase biointegration. To step away from the need for donor material, synthetic keratoprostheses with soft skirts have been introduced to increase biointegration between the device and native tissue. The AlphaCor™, a synthetic polymer (PHEMA) hydrogel, addressed certain complications of the previous versions of keratoprostheses but resulted in stromal melting and optic deposition. Efforts are being made towards creating synthetic keratoprostheses that emulate native corneas by the inclusion of biomolecules that support enhanced biointegration of the implant while reducing stromal melting and optic deposition. The field continues to shift towards more advanced bioengineering approaches to form replacement corneas. Certain biomolecules such as collagen are being investigated to create corneal substitutes, which can be used as the basis for bio-inks in 3D corneal bioprinting. Alternatively, decellularised corneas from mammalian sources have shown potential in replicating both the corneal composition and fibril architecture. This review will discuss the limitations of keratoplasty, milestones in the history of artificial corneal development, advancements in current artificial corneas, and future possibilities in this field.

Keyhole Anterior Lamellar Keratoplasty for Boston Keratoprosthesis Corneal Melt

Corneal melt remains a challenging complication of Boston keratoprosthesis (KPro) and may lead to disastrous consequences such as endophthalmitis, KPro extrusion, and permanent loss of vision. Several procedures have been suggested to repair established melts; however, KPro removal or exchange is often required due to high recurrence. We herein describe a novel surgical technique to repair corneal melt: a lamellar corneal graft is centrally trephined, and a radial cut is extended from the central opening to create a keyhole graft. The graft is draped around the KPro and tightly secured around the central stem. The radial cut is closed with sutures, and the graft is secured into the underlying tissue with fibrin glue and sutures. The graft remains stable with the KPro in place, while the patients maintain a 20/200 vision or better at two years. This technique is a useful alternative for securing KPro and preventing corneal melt recurrence.

CorNeat KPro: Ocular Implantation Study in Rabbits

PURPOSE

The purpose of this study was to evaluate surgical feasibility and long-term integration of the CorNeat Keratoprosthesis (KPro), a novel synthetic cornea, in rabbits.

METHODS

The CorNeat KPro is a synthetic corneal implant designed to treat corneal blindness by using a polymeric scaffold for biointegration, consequently assimilating synthetic optics within ocular tissues. Eight New Zealand White rabbits were implanted unilaterally with the CorNeat KPro and observed for 6 months. Animals were regularly monitored by a certified ophthalmologist using slit-lamp biomicroscopy. One animal developed postoperative endophthalmitis and was removed from the study 7 weeks postsurgery. At termination, eyes were enucleated and evaluated histologically to assess local tissue integration and inflammatory response.

RESULTS

The surgical procedure was found feasible. The CorNeat KPro integrated into all operated eyes, resulting in a retention rate of 87.5% at the conclusion of the 6-month follow-up period. We observed minimal-to-mild conjunctival and iridial congestion and did not find additional inflammatory indicators, such as anterior chamber fibrin, flare, or cells. The optical element of the device remained clear with zero incidence of retroprosthetic membrane formation. Histopathological evaluation revealed comparable tissue and cellular reaction in all eyes, consisting of the presence of fibroblasts and associated collagen fibrils within the device's skirt component. Some eyes showed a mild foreign body reaction surrounding the skirt.

CONCLUSIONS

Clinical and histological findings indicate the integration of the implanted device into the surrounding tissue, evident by the retention rate and the diffuse infiltration of fibroblasts with collagen deposition among the device's fibrils. These data hold promise for clinical application in humans.

Challenges in management of the Boston Keratoprosthesis Type 1

PURPOSE OF REVIEW

The Boston Keratoprosthesis Type 1 was pioneered by Claes Dohlman several decades ago. Since its inception, the device has undergone multiple revisions to address challenges associated with retroprosthetic membrane formation, retention, extrusion, stromal melt and endophthalmitis. Although visual outcomes and retention rates have improved, challenges, especially glaucoma, remain.

RECENT FINDINGS

The Boston Keratoprosthesis Type I device has seen an increase in popularity because of the improvement in rates of retention and visual rehabilitation. Recent outcome studies have allowed clinicians to identify diagnoses and indications that can lead to more favorable results with the Boston Keratoprosthesis Type I device.

SUMMARY

The Boston Keratoprosthesis Type I device continues to play a vital role in visual rehabilitation for eyes with very low chance of realistic allograft survival -- such as in eyes where corneal grafting is considered high-risk: eyes with corneal limbal stem cell failure, extensive deep corneal stromal neovascularization, and multiple allograft failures. This review article summarizes the perioperative and postoperative challenges, as well as other considerations associated with the device.

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.

Long-term outcomes of Boston keratoprosthesis type I: the Chinese People's Liberation Army General Hospital experience

PURPOSE

To report the long-term outcomes of Boston keratoprosthesis type I (B-KPro type I) implantation in the management of severe ocular surface disorders.

METHODS

Retrospective case series. Patients who underwent B-KPro type I implantation at the People's Liberation Army General Hospital were enrolled between March 2011 and September 2019. Data regarding visual acuity (VA), B-KPro type I retention and postoperative complications were recorded and analysed.

RESULTS

A total of 103 eyes of 100 patients who underwent B-KPro type I implantation were included. The main indications were chemical burn (59.2%), ocular trauma (25.2%), herpetic keratitis (11.7%) and autoimmune diseases (3.9%). The percentage of eyes with postoperative VA of 10/200 or better was 82.7% at 6 months, 82.8% at 12 months, 77.9% at 2 years, 72.4% at 3 years, 71.1% at 4 years, 69.4% at 5 years, 58.9% at 6 years, 56.8% at 7 years and 42.9% at 8 years. Preoperatively, 8.7% eyes were diagnosed with new-onset glaucoma. Retroprosthetic membrane formation occurred in 19.4% eye. Corneal melting occurred in 18.4% eyes. Sterile vitritis was diagnosed in 4.9% eyes and infectious endophthalmitis in 2.9% eyes. Retinal detachment occurred in 0.9% eyes.

CONCLUSIONS

In a Chinese patient group, B-KPro type I is a viable option for treating severe ocular surface disorders in eyes where conventional keratoplasty would have a poor prognosis, especially in patients with chemical and thermal burns. Improved visual outcomes and high retention rate can be achieved and maintained in most cases.

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.

Estimation of Goldmann applanation tonometer intraocular pressure (IOP) from scleral Schiotz IOP values in eyes with type-1 keratoprostheses

PURPOSE

To validate estimation of Goldmann applanation tonometer (GAT) intraocular pressure (IOP) from scleral Schiotz IOP measurements using a regression model in normal eyes and eyes with type-1 keratoprostheses.

METHODS

In this prospective cross-sectional study, cohort-1 had 253 normal anterior segment eyes, and cohort-2 had 100 eyes with type-1 keratoprostheses. Scleral Schiotz IOP measurements were used (in a non-linear model) to predict GAT IOP values for these eyes. Accuracy of predicted GAT IOP values was assessed using actual GAT IOP values for normal eyes, while for type-1 keratoprosthetic eyes, finger tension (FT) IOP assessments by an experienced glaucoma specialist were used. Primary outcome was agreement between FT IOP (assessed by an experienced glaucoma specialist) and predicted GAT IOP-derived clusters.

RESULTS

The actual values of GAT IOP measurements in normal eyes (n=253; mean age ±SD, 51.35±15.56 years) ranged between 6 mm Hg and 62 mm Hg (mean=22±10.05 mm Hg). Estimated and actual GAT IOP values for normal eyes were very similar (mean difference=0.05 mm Hg with limits of agreement: -5.39 to 5.5 by Bland-Altman plot). Of the 100 eyes with type-1 keratoprostheses, 68 were classified as having digitally normal IOP, 28 as borderline and 4 as high. The agreement between classification by FT assessment and model-predicted GAT IOP values was substantial (Kappa=0.81, 95% CI 0.69 to 0.93). The accuracy of the model in assessing IOP was found to be 91% (95% CI 0.84 to 0.96).

CONCLUSION

Scleral Schiotz IOP values along with our predictive model can be an alternative objective method to FT IOP in assessing IOP in eyes with type-1 keratoprostheses.

Transmucosal Boston Keratoprosthesis Type I in a Patient With Advanced Ocular Cicatricial Pemphigoid

PURPOSE

To describe a novel surgical technique using the Boston Keratoprosthesis (KPro) type I in a patient with advanced ocular cicatricial pemphigoid (OCP) using oral mucosa for covering the prosthesis.

METHODS

We present the case of an 85-year-old man previously diagnosed with type 2 diabetes and advanced OCP nonresponsive to immunosuppressive treatment, whose best-corrected visual acuity was light perception and projection in both eyes. After examination, Boston KPro type I in the right eye was contemplated because osteo-odonto KPro and Tibial bone KPro were not feasible because of the patient's osteoporosis and edentulism. Reconstruction of the ocular surface was first performed using oral mucosa to release the symblepharon and try to deep the fornices. Three months later, the oral mucosa was lifted, and the Boston KPro type I was implanted using the patient's own cornea. Then, a modification of the standard surgical technique was carried out, replacing the use of contact lens for covering the prosthesis with an oral mucosa graft with a central trephination as an alternative option in fornix foreshortening cases.

RESULTS

After 11 months, visual acuity was stable to 0.2 decimal. No postoperative complications have been encountered, and prosthesis was in place.

CONCLUSIONS

The surgical technique of transmucosal Boston KPro type I may be considered a surgical alternative in patients with advanced OCP who present with severe fornix foreshortening, where osteo-odonto KPro or Tibial bone KPro cannot be performed due to osteoporosis or edentulism or when the Boston KPro type II is not readily available.

Implantable self-aligning fiber-optic optomechanical devices for in vivo intraocular pressure-sensing in artificial cornea

Artificial cornea is an effective treatment of corneal blindness. Yet, intraocular pressure (IOP) measurements for glaucoma monitoring remain an urgent unmet need. Here, we present the integration of a fiber-optic Fabry-Perot pressure sensor with an FDA-approved keratoprosthesis for real-time IOP measurements using a novel strategy based on optical-path self-alignment with micromagnets. Additionally, an alternative noncontact sensor-interrogation approach is demonstrated using a bench-top optical coherence tomography system. We show stable pressure readings with low baseline drift (<2.8 mm Hg) for >4.5 years in vitro and efficacy in IOP interrogation in vivo using fiber-optic self-alignment, with good initial agreement with the actual IOP. Subsequently, IOP drift in vivo was due to retroprosthetic membrane (RPM) formation on the sensor secondary to surgical inflammation (more severe in the current pro-fibrotic rabbit model). This study paves the way for clinical adaptation of optical pressure sensors with ocular implants, highlighting the importance of controlling RPM in clinical adaptation.

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.

The Aurolab Keratoprosthesis (KPro) versus the Boston Type I Kpro: 5-year Clinical Outcomes in 134 Cases of Bilateral Corneal Blindness

PURPOSE

To compare the clinical outcomes of Boston Type I keratoprosthesis (Boston Kpro) with its low-cost version, the Aurolab Kpro (auroKPro).

DESIGN

Retrospective comparative case series.

METHODS

This study included 134 eyes of 130 patients with severe bilateral corneal blindness but with wet ocular surfaces. The patients underwent either Boston Kpro (n = 78) or auroKPro (n = 56) implantation based on the device availability and patient's affordability. The primary outcome measurements were anatomical retention (defined as absence of device extrusion, exchange, or explantation) and functional recovery of 20/200 or better visual acuity at yearly time points until 5-years of follow-up.

RESULTS

Limbal stem cell deficiency was the most common indication (60.5%) for surgery, followed by multiple failed grafts (35%). Both groups were comparable at baseline with respect to indications for surgery and associated ocular co-morbidities (P > 0.05). The overall anatomical retention rates were similar in the Boston Kpro (55 of 78, 70.5%) and auroKPro (35 of 56, 62.5%) groups (P = 0.11). Kaplan-Meier survival rates at 5 years of follow-up were greater for the Boston Kpro with respect to both anatomical retention (63 ± 6% vs. 43.4 ± 10%, respectively; P = 0.057) and functional recovery (42.4 ± 6% vs. 32.2 ± 7%, respectively; P = 0.345), but these differences were not statistically significant. Complications such as intraoperative device breakage (7%) and postoperative extrusions (12.5%) were significantly more common with the auroKPro (P = 0.023).

CONCLUSIONS

Both the auroKPro and the Boston Kpro are effective treatment options for patients with severe bilateral corneal blindness. The auroKPro can be considered an alternative to the Boston Kpro when affordability or availability of the Boston Kpro is a limiting factor.

Three-Dimensional Optical Coherence Tomography Imaging For Glaucoma Associated With Boston Keratoprosthesis Type I and II

PRECIS

Three-dimensional (3D) spectral domain optical coherence tomography (OCT) volume scans of the optic nerve head (ONH) and the peripapillary area are useful in the management of glaucoma in patients with a type I or II Boston Keratoprosthesis (KPro).

PURPOSE

The purpose of this study was to report the use of spectral domain OCT in the management of glaucoma in patients with a type I or II Boston KPro.

MATERIALS AND METHODS

This study is an observational case series. Four consecutive patients with KPro implants were referred for glaucoma evaluation. A comprehensive eye examination was performed which included disc photography, visual field testing, and high-density spectral domain OCT volume scans of the ONH and the peripapillary area. 2D and 3D parameters were calculated using custom-designed segmentation algorithms developed for glaucoma management.

RESULTS

Spectral domain OCT parameters provided useful information in the diagnosis and management of 4 KPro patients. OCT parameters which can be used in KPro patients included 2D retinal nerve fiber layer (RNFL) thickness, 3D peripapillary RNFL volume, 3D peripapillary retinal thickness and volume, 3D cup volume, and 3D neuroretinal rim thickness and volume. In 3 of 4 cases where the traditional 2D RNFL thickness scan was limited by artifacts, 3D spectral domain OCT volume scans provided useful quantitative objective measurements of the ONH and peripapillary region. Therefore, 3D parameters derived from high-density volume scans as well as radial scans of the ONH can be used to overcome the limitations and artifacts associated with 2D RNFL thickness scans.

CONCLUSIONS

Spectral domain OCT volume scans offer the possibility to enhance the evaluation of KPro patients with glaucoma by using both 2D and 3D diagnostic parameters that are easily obtained in a clinic setting.

[Boston type I keratoprosthesis implantation technique : Video article]

BACKGROUND

Keratoprosthetics refer to the replacement of human corneal tissue with an artificially produced exchange product. The most widely implanted keratoprosthesis worldwide is the Boston Type I Keratoprosthesis (BI-KPro, Massachusetts Eye and Ear Infirmary, Boston, MA, USA).

METHODS

This video article demonstrates the surgical technique of BI-KPro implantation as routinely performed at this institution. In addition, an overview of the surgical indications, patient consent, anesthesia and positioning, postoperative treatment and complications as well as the evidence of the technique is provided in the article based on experience with 31 BI-KPro implantations.

RESULTS

The indications for BI-KPro primarily include patients in a high-risk keratoplasty setting particularly after repeatedly failed keratoplasty. A thorough patient examination and assessment of the indications as well as detailed disclosure of information to the patient about the individual prognosis, the risk profile, the postoperative therapy and follow-up enable a positive postoperative result.

CONCLUSION

The BI-KPro provides an established and relatively standardized option for surgical treatment of eyes in a high-risk keratoplasty setting. Patients should be preoperatively informed with respect to the individual prognosis, complication profile and life-long follow-up.

Diagnostic criteria for limbal stem cell deficiency before surgical intervention-A systematic literature review and analysis

An accurate diagnosis of limbal stem cell deficiency (LSCD) is the premise of an appropriate treatment; however, there is no consensus about the diagnostic criteria for LSCD. We performed a systematic literature search of the peer-reviewed articles on PubMed, Medline, and Ovid to investigate how LSCD was diagnosed before surgical intervention. The methods used to diagnose LSCD included clinical presentation, impression cytology, and in vivo confocal microscopy. Among 131 eligible studies (4054 eyes), 26 studies (459 eyes, 11.3%) did not mention the diagnostic criteria. In the remaining 105 studies, the diagnosis of LSCD was made on the basis of clinical examination alone in 2398 eyes (62.9%), and additional diagnostic tests were used in 1047 (25.8%) eyes. Impression cytology was used in 981 eyes (24.2%), in vivo confocal microscopy was used in 29 eyes (0.7%), and both impression cytology and in vivo confocal microscopy were used in 37 eyes (0.9%). Our findings suggest that only a small portion of patients underwent a diagnostic test to confirm the diagnosis of LSCD. Treating physicians should be aware of the limitations of clinical examination in diagnosing LSCD and perform a diagnostic test whenever possible before surgical intervention.

Fibrosis: Shared Lessons From the Lens and Cornea

Regenerative repair in response to wounding involves cell proliferation and migration. This is followed by the reestablishment of cell structure and organization and a dynamic process of remodeling and restoration of the injured cells' extracellular matrix microenvironment and the integration of the newly synthesized matrix into the surrounding tissue. Fibrosis in the lungs, liver, and heart can lead to loss of life and in the eye to loss of vision. Learning to control fibrosis and restore normal tissue function after injury repair remains a goal of research in this area. Here we use knowledge gained using the lens and the cornea to provide insight into how fibrosis develops and clues to how it can be controlled. The lens and cornea are less complex than other tissues that develop life‐threatening fibrosis, but they are well characterized and research using them as model systems to study fibrosis is leading toward an improved understanding of fibrosis. Here we summarize the current state of the literature and how it is leading to promising new treatments. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Post-operative outcomes associated with Boston type 1 keratoprosthesis implantation in Northeast China

The aim of the present study was to investigate the post-operative outcomes associated with Boston type 1 keratoprosthesis (Kpro-1) implantation in the treatment of patients with corneal blindness in Northeast China. Clinical data of patients who had undergone Kpro-1 implantation between July 2010 and November 2014 were retrospectively collected. The visual performance, implant retention and post-surgical complications were recorded for each patient. A total of 20 patients (20 eyes) with corneal blindness were included in the study. Prior to surgery, the patients exhibited poor vision and decreased levels of light perception. At 3 days, 1 month, 6 months, 1 year and 2 years post-surgery, logarithm of the minimum angle of resolution values were significantly decreased compared with the pre-operative values. The initial Kpro-1 implants were retained in 16 eyes. Regarding the post-operative complications, six patients exhibited retroprosthetic membrane formation, two patients presented with endophthalmitis, two patients developed secondary glaucoma, two patients experienced optical cylinder detachment, two patients presented with corneal melting, three patients had retinal detachment, three patients developed corneal ulcers and one patient had secondary optic neuropathy. Overall, the results of the present study suggested that implantation with Kpro-1 may represent an alternative therapeutic strategy for patients following previously failed keratoplasty in Northeast China. Serious complications associated with Kpro-1 implantation are common, and thus, suitable patient selection, continuous follow-up and early treatment interventions are recommended.

Universal Corneal Epithelial-Like Cells Derived from Human Embryonic Stem Cells for Cellularization of a Corneal Scaffold

Purpose

We generated universal corneal epithelial cells (CEC) from human embryonic stem cells (hESC) by genetically removing human leukocyte antigens (HLA) class I from the cell surface.

Methods

The serum-free, growth factor-free, and defined medium E6 was used to differentiate hESC to CEC. Decellularized murine corneas were recellularized with hESC-derived CEC. Using CRISPR/Cas9, β-2-microglobulin (B2M) was deleted in hESC to block the assembly of HLA class-I antigens on the cell surface to generate B2M^−/− CEC.

Results

E6 alone was sufficient to allow hESC differentiation to CEC. A time-course analysis of the global gene expression of the differentiating cells indicates that the differentiation closely resembles the corneal development in vivo. The hESC-CEC were highly proliferative, and could form multilayer epithelium in decellularized murine cornea, retain its transparency, and form intact tight junctions on its surface. As reported before, B2M knockout led to the absence of HLA class-I on the cell surface of hESC and subsequently derived CEC following stimulation with inflammatory factors. Moreover, B2M^−/− CEC, following transplantation into mouse eyes, caused less T-cell infiltration in the limbal region of the eye than the wild-type control.

Conclusions

CEC can be derived from hESC via a novel and simple protocol free of any proteins, hESC-CEC seeded on decellularized animal cornea form tight junctions and allow light transmittance, and B2M^−/− CEC are hypoimmunogenic both in vitro and in vivo.

Translational Relevance

B2M^−/− hESC-CEC can be an unlimited and universal therapy for corneal repair in patients of any HLA type.

[The Boston keratoprosthesis in the management of corneal blindness: Indications and limitations]

INTRODUCTION

Keratoprostheses offer a therapeutic alternative to patients with bilateral corneal blindness who cannot undergo corneal allograft. The goal of this work was to evaluate the indications and limitations of Boston keratoprosthesis.

MATERIALS AND METHODS

Seven patients underwent unilateral implantation of a Boston type I keratoprosthesis between December 2012 and November 2016. The following data were collected: surgical indication, preoperative visual acuity, postoperative visual acuity at D1, D7, D30, 6 months and 12 months, complications and postoperative treatment.

RESULTS

The mean age of implantation was 58.7±23.4 years. The surgical indications included 1 case of congenital bilateral aniridia, 2 cases of chemical burn and 4 graft decompensations after multiple keratoplasties. Preoperative visual acuity was limited to "light perception" in 6 cases and "hand motion" in one case. A gain in visual acuity was observed in 4 patients, which corresponded to a mean gain of 1.53 logMAR at last follow-up. Postoperative visual acuity averaged 2.33 logMAR. All patients experienced an improvement in their quality of life and independence.

DISCUSSION

Patients should be selected carefully, favoring patients with a remaining functional potential and able to engage in close postoperative follow-up, in order to ensure the best possible treatment success.

CONCLUSION

Boston keratoprosthesis provides improved vision and improved quality of life for patients suffering from bilateral corneal blindness.

Patch graft using collagen matrix (Ologen) for glaucoma drainage device exposure in a patient with Boston Keratoprosthesis type 1

Purpose

To report the first successfully treated case of recurrent tube exposure in a patient with the Boston Keratoprosthesis type 1 with a collagen matrix patch graft (Ologen).

Observations

A 50 year-old female with a Boston Keratoprosthesis type 1 and a history of Axenfeld-Reiger syndrome presents to our department with recurrent glaucoma drainage device exposure in her left eye. After failed spontaneous closure with topical antibiotics and lubricants, she undergoes tube exposure repair using an Ologen patch graft. Surgery was successful and the patient did not have any recurrence up to last follow-up two years post-operatively.

Conclusion

Collagen matrix patch graft seems to be advantageous in treating glaucoma tube exposure in the Boston KPro eye, which is often a more challenging entity to treat.

Importance

Collagen matrix patch graft could be considered as a primary patch graft in treating tube exposure in eyes with the Boston KPro.

Keratoprosthesis: Current global scenario and a broad Indian perspective

Keratoprosthesis (Kpro) forms the last resort for bilateral end-stage corneal blindness. The Boston Type 1 and 2 Kpros, the modified osteo-odonto Kpro and the osteo-Kpro are the more frequently and commonly performed Kpros, and this review attempts to compile the current data available on these Kpros worldwide from large single-center studies and compare the indications and outcomes with Kpros in the Indian scenario. Although the indications have significantly expanded over the years and the complications have reduced with modifications in design and postoperative regimen, these are procedures that require an exclusive setup, and a commitment toward long-term follow-up and post-Kpro care. The last decade has seen a surge in the number of Kpro procedures performed worldwide as well as in India. There is a growing need in our country among ophthalmologists to be aware of the indications for Kpro to facilitate appropriate referral as well as of the procedure to enable basic evaluation during follow-ups in case the need arises, and among corneal specialists interested to pursue the field of Kpros in understanding the nuances of these surgeries and to make a judicious decision regarding patient and Kpro selection and more importantly deferral.

Assessment of Glaucomatous Damage After Boston Keratoprosthesis Implantation Based on Digital Planimetric Quantification of Visual Fields and Optic Nerve Head Imaging

PURPOSE

To investigate glaucomatous damage in Boston keratoprosthesis type I (KPro) patients through structural analysis of the optic nerve head and digital planimetric quantification of Goldmann visual fields, a novel method of monitoring perimetric changes in KPro patients.

METHODS

Records of patients undergoing KPro implantation from 2007 to 2015 at a single institution were reviewed. Parameters related to glaucoma status and KPro outcomes were analyzed.

RESULTS

Twenty-two eyes from 21 patients met inclusion criteria, with mean follow-up of 49.4 months (range 15-90). Mean results for the following parameters before KPro implantation and at last follow-up were (pre-KPro; at last follow-up): best-corrected visual acuity (2.07; 0.70 logMAR), number of glaucoma medications (1.14; 1.05), intraocular pressure (IOP) (18.4; 18.4 mm Hg), vertical cup-to-disc ratio (C/D) (0.48; 0.50), and horizontal C/D (0.52; 0.52). IOP-lowering procedures were performed pre-KPro (5/22), concurrently with KPro (10/22), post-KPro (6/22), or never (6/22). An increase in C/D ≥0.1 and loss of V4e isopter area >30% occurred in 22.7% and 12.5%, respectively. Development of post-KPro glaucoma, progression of preexisting or post-KPro glaucoma, and no glaucoma development as evidenced by an objective assessment of structural and functional parameters were seen in 2/22 (9.1%), 7/22 (31.8%), and 6/22 (27.3%) eyes, respectively.

CONCLUSIONS

Clinicians should strive to vigilantly monitor for glaucoma despite the inherent difficulties in tonometry, optic nerve visualization and imaging, and visual field testing in KPro patients. Meticulous glaucoma surveillance with structural and functional testing combined with earlier IOP-lowering surgical intervention may result in decreased rates of glaucomatous vision loss in KPro patients.

Recent advances and anaesthetic considerations in corneal transplantation

Significant surgical advances have been made recently in corneal transplantation. Penetrating keratoplasty was the dominant method from 1905, until selective lamellar keratoplasty emerged as the preferred technique over the last 20 years. Advanced techniques such as corneal limbal stem cell transplant and keratoprosthesis are also available. The major surgical complications of corneal transplantation are extrusion of ocular content and expulsive choroidal haemorrhage. It is essential for an ophthalmic anaesthetist to have a good understanding of these new surgical procedures so as to provide optimal surgical conditions. This article aims to inform anaesthetists about the recent surgical advances in corneal transplantation and explore the anaesthetic considerations of these new techniques. General anaesthesia remains suitable for a wide range of these procedures especially in repeat surgery, difficult, or prolonged procedures. Regional ophthalmic blocks are ideal for endothelial keratoplasty but can be used in penetrating keratoplasty based on individual risk-benefit assessment, and as a supplement to general anaesthesia. Topical anaesthesia provides an alternative when general anaesthesia and ophthalmic regional blocks are less desirable but overall its use is limited.

Retroprosthetic Membrane Formation in Boston Keratoprosthesis: A Case-Control-Matched Comparison of Titanium Versus PMMA Backplate

PURPOSE

Retroprosthetic membrane (RPM) formation is the most common complication after Boston type 1 keratoprosthesis (KPro) implantation. It affects visual acuity and can predispose to corneal melt. Two KPro backplate materials are available: titanium and polymethyl methacrylate (PMMA). This study investigates the influence of the KPro backplate material on visually significant RPM formation.

METHODS

A retrospective case-control-matched study involving 40 patients; 20 eyes implanted with a titanium backplate KPro were case-matched with 20 eyes implanted with a PMMA backplate KPro between 2007 and 2015 with 1-year minimum follow-up.

RESULTS

The mean follow-up duration was 28.1 ± 8.9 and 53.6 ± 24.3 months in the titanium and PMMA groups, respectively. At 12 months postoperatively, 7 eyes with titanium and 6 eyes with PMMA backplates developed a visually significant RPM. By the end of the study, a total of 11 eyes with titanium and 9 eyes with PMMA KPros developed a visually significant RPM. There was no statistically significant difference between both groups. Three of 11 eyes with titanium KPros that had a visually significant RPM required surgical membranectomy, whereas all eyes with PMMA KPros were successfully treated with the yttrium-aluminum-garnet laser. Recurrence of RPMs was found in 7/11 eyes in the titanium group and 2/9 eyes in the PMMA group with no statistical significance.

CONCLUSIONS

Titanium backplate KPros do not significantly reduce RPM formation compared with PMMA backplate KPros in a case-control-matched setting. A larger prospective study is warranted to evaluate comparative long-term performance and guide newer designs.