Donor source affects the outcome of ocular surface reconstruction in chemical or thermal burns of the cornea11The authors do not have any proprietary interest in the products mentioned used in this study

Healing the cornea: Exploring the therapeutic solutions offered by MSCs and MSC-derived EVs

Affecting a large proportion of the population worldwide, corneal disorders constitute a concerning health hazard associated to compromised eyesight or blindness for most severe cases. In the last decades, mesenchymal stem/stromal cells (MSCs) demonstrated promising abilities in improving symptoms associated to corneal diseases or alleviating these affections, especially through their anti-inflammatory, immunomodulatory and pro-regenerative properties. More recently, MSC therapeutic potential was shown to be mediated by the molecules they release, and particularly by their extracellular vesicles (EVs; MSC-EVs). Consequently, using MSC-EVs emerged as a pioneering strategy to mitigate the risks related to cell therapy while providing MSC therapeutic benefits. Despite the promises given by MSC- and MSC-EV-based approaches, many improvements are considered to optimize the therapeutic significance of these therapies. This review aspires to provide a comprehensive and detailed overview of current knowledge on corneal therapies involving MSCs and MSC-EVs, the strategies currently under evaluation, and the gaps remaining to be addressed for clinical implementation. From encapsulating MSCs or their EVs into biomaterials to enhance the ocular retention time to loading MSC-EVs with therapeutic drugs, a wide range of ground-breaking strategies are currently contemplated to lead to the safest and most effective treatments. Promising research initiatives also include diverse gene therapies and the targeting of specific cell types through the modification of the EV surface, paving the way for future therapeutic innovations. As one of the most important challenges, MSC-EV large-scale production strategies are extensively investigated and offer a wide array of possibilities to meet the needs of clinical applications.

Midterm results after allogeneic simple limbal epithelial transplantation from deceased-donor eyes in patients with persistent corneal epithelial defects due to limbal stem cell deficiency

BACKGROUND

This study aims to characterize the clinical outcomes after allogeneic simple limbal epithelial transplantation (alloSLET) utilizing tissue from cadaveric donor eyes to address persistent corneal epithelial defects caused by limbal stem cell deficiency.

METHODS

We conducted a retrospective analysis of medical records from 20 patients, encompassing 24 eyes, who underwent alloSLET at least 2 years prior. The primary endpoint was the achievement of complete epithelialization of the corneal surface by corneal epithelium. Secondary endpoints included corrected distance visual acuity (CDVA) and postoperative adverse events.

RESULTS

The median postoperative follow-up period was 36 months (range, 24-74 months). At 1, 3 and 6 months post-surgery, 96% of eyes demonstrated epithelialized corneal surfaces, which declined to 71% at 12 months, to 54% at 24 and 36 months after surgery, and to 50% thereafter. There were no significant differences in graft survival between alloSLET performed alone versus in combination with penetrating keratoplasty. However, instances of graft failure were associated with postoperative elevated intraocular pressure (IOP) and a history of multiple amniotic membrane and corneal graft transplants.

CONCLUSIONS

AlloSLET emerges as a viable mid-term intervention for limbal stem cell deficiency-associated non-healing corneal epithelial defects in the absence of autologous limbal tissue. Our findings underscore the increased risk of graft failure in patients with elevated IOP and a background of multiple previous amniotic membrane and corneal graft procedures.

Biology and medicine on ocular surface restoration: Advancements and limits of limbal stem cell deficiency treatments

Ocular vision can be hampered by corneal damages, sensibly reducing patients' quality of life and having important social and economic consequences. Ocular surface diseases, which often lead to corneal opacities with visual impairment are the most severe forms of the Limbal Stem Cell Deficiency (LSCD). The present review provides an updated perspective on the available treatments for LSCD, focusing on clinical and biological features, as well as critical points to monitor during clinical translation. Recently developed surgical treatments for LSCD are described, along with their benefits and limitations, with the aim of addressing the issue of correct patient selection. Autologous surgical approaches have been attempted, such as conjunctival limbal autograft (CLAU), simple limbal epithelial transplantation (SLET), and others. Allogeneic limbal stem cell transplantation represents an alternative but carries risk of rejection and requires immunosuppression. Other potential treatments are based on induced pluripotent stem cells (iPSCs), but they require further investigation. The development of advanced therapy medicinal products (ATMPs) such as cultivated limbal epithelial transplantation (CLET), or the use of other epithelia as cultivated oral mucosal epithelial cell transplantation (COMET), has opened additional therapeutic possibilities. Some common critical issues in clinical translation are described, such as patient selection, biopsy procurement, or the use of human/animal derived components, which require rigorous validation to ensure safety and efficacy. Personalized medicine is a promising field for ocular surface restoration, where long-term follow-up studies and standardized criteria are crucial to evaluate the efficacy of these treatments and their cost-effectiveness in providing high-value healthcare.

Limbal graft transplantation: a rare implementation in pediatric limbal stem cell deficiency

PURPOSE

To evaluate limbal graft transplantation success in pediatric patients with chemical injury-induced limbal stem cell deficiency (LSCD) using the 'LSCD Working Group' staging system.

METHODS

Medical records of 11 eyes of 11 children who underwent limbal graft transplantation (limbal autograft/limbal allograft) were included. Surgical success was defined as improvement in the post-operative 1st year LSCD stage.

RESULTS

The mean age was 12 ± 5 (4-17) years. Causative agent was alkaline in 4(36.4%) and acid in 3(27.2%) patients. Limbal autograft was performed in 9 (81.8%) eyes with unilateral LSCD, and allograft transplantation was performed in 2 (18.2%) eyes with bilateral LSCD. The mean follow-up time was 33.89 ± 30.73 (12-102.33) months. The overall limbal graft transplantation success rate was 72.7%. Among 9 patients who receive limbal autograft, 8 had improvement in post-operative LSCD stage, 1 had stable LSCD stage. Of the 2 patients who receive limbal allograft, post-operative LSCD stage remained the same in 1 and worsened in 1 patient. The mean time between injury and the surgery was 30.47 ± 30.08 (7-108.47) months. Penetrating keratoplasty was performed in 3 (27.2%) of 11 patients following limbal graft transplantation.

CONCLUSION

Management of LSCD in children is challenging and appears to be somewhat different from that of adults. Limited data in the literature indicate that cultivated or simple limbal epithelial transplantations (CLET/SLET) are primarily preferred in children. Although the tendency to take small tissue from the healthy eye is noteworthy, conventional limbal allograft and autograft transplantations also show promising results without any further complications in at least 1 year follow-up period.

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.

Amnion-derived hydrogels as a versatile platform for regenerative therapy: from lab to market

In recent years, the amnion (AM) has emerged as a versatile tool for stimulating tissue regeneration and has been of immense interest for clinical applications. AM is an abundant and cost-effective tissue source that does not face strict ethical issues for biomedical applications. The outstanding biological attributes of AM, including side-dependent angiogenesis, low immunogenicity, anti-inflammatory, anti-fibrotic, and antibacterial properties facilitate its usage for tissue engineering and regenerative medicine. However, the clinical usage of thin AM sheets is accompanied by some limitations, such as handling without folding or tearing and the necessity for sutures to keep the material over the wound, which requires additional considerations. Therefore, processing the decellularized AM (dAM) tissue into a temperature-sensitive hydrogel has expanded its processability and applicability as an injectable hydrogel for minimally invasive therapies and a source of bioink for the fabrication of biomimetic tissue constructs by recapitulating desired biochemical cues or pre-defined architectural design. This article reviews the multi-functionality of dAM hydrogels for various biomedical applications, including skin repair, heart treatment, cartilage regeneration, endometrium regeneration, vascular graft, dental pulp regeneration, and cell culture/carrier platform. Not only recent and cutting-edge research is reviewed but also available commercial products are introduced and their main features and shortcomings are elaborated. Besides the great potential of AM-derived hydrogels for regenerative therapy, intensive interdisciplinary studies are still required to modify their mechanical and biological properties in order to broaden their therapeutic benefits and biomedical applications. Employing additive manufacturing techniques (e.g., bioprinting), nanotechnology approaches (e.g., inclusion of various bioactive nanoparticles), and biochemical alterations (e.g., modification of dAM matrix with photo-sensitive molecules) are of particular interest. This review article aims to discuss the current function of dAM hydrogels for the repair of target tissues and identifies innovative methods for broadening their potential applications for nanomedicine and healthcare.

Evaluation of the factors that influence surgical outcome in conjunctival-limbal allograft transplantation

OBJECTIVE

To evaluate the surgical results and the variables affecting the outcomes in conjunctival-limbal allograft transplantation (CLAL).

METHODS

Patients who underwent CLAL for limbal stem cell deficiency (LSCD) between 2007 and 2019 were included in the study. LSCD staging was performed according to the staging system developed by the 'Limbal Stem Cell Working Group'. Stage 1C and higher stage LSCD patients were included in the study. 'Successful surgical outcome' was defined as improvement in LSCD stage at 1 year postoperatively.

RESULTS

A total of 19 eyes of 19 LSCD patients were included. The mean age of the patients was 40.21 ± 14.65 (6-65) years, and the male/female ratio was 12/7. CLAL was performed in 9 (47.3%) patients with Stage 2B, 9 (47.3%) patients with Stage 3 and 1 (5.4%) with Stage 1C. LSCD aetiology; chemical injury (12), vernal keratoconjunctivitis (2), aniridia (1), corneal degeneration (1), and unknown (3). Surgery was successful in 52.6% of cases. Surgical success was associated with lower LSCD stage (p = 0.04). Lower grades of chemical injury at presentation and a longer time interval between injury and CLAL were associated with higher surgical success (p = 0.001; p = 0.001). The mean postoperative follow-up time was 50.77 ± 29.46 (6-98) months.

CONCLUSIONS

Despite graft rejection and long-term use of immunosuppressants, CLAL is still one of the most preferred techniques in the treatment of bilateral LSCD. Preoperative LSCD stage and degree of chemical burn are important factors affecting the surgical outcome. Also, CLAL surgery should not be rushed and should be performed when inflammation has subsided.

Outcomes of Combined Penetrating Keratoplasty and Limbal Stem Cell Transplantation: A Meta-Analysis on Simultaneous Versus Sequential Surgery

PURPOSE

The objective of this study is to perform a systematic review and meta-analysis of the published studies on limbal stem cell transplantation (LSCT) combined with penetrating keratoplasty (PK) performed either simultaneously or sequentially.

METHODS

An extensive search was conducted in the MEDLINE and Google Scholar databases. Prospective and retrospective trials and case series reporting on the outcomes of LSCT with PK were included. Primary outcomes were the stability of the ocular surface and the rejection and/or failure of the corneal graft.

RESULTS

A total of 209 eyes from 13 studies were included in the simultaneous group and 489 eyes from 33 studies in the sequential group. Ocular surface stability was 88% [95% confidence interval (CI), 79%-96%] for sequential cases and 64% (95% CI, 43%-82%) for simultaneous cases ( P = 0.001). The graft failure rate was 15% (95% CI, 6%-26%) for sequential cases and 44% (95% CI, 31%-58%) for simultaneous cases ( P < 0.001). For cases performed sequentially, subgroup analysis revealed a stable ocular surface in 97% (95% CI, 91%-100%) of autograft cases and 63% (95% CI, 45%-80%) of allograft cases ( P < 0.001). The graft failure rate in sequential cases was 7% (95% CI, 0%-18%) for autografts and 34% (95% CI, 18%-52%) for allografts ( P < 0.001).

CONCLUSIONS

Sequential LSCT followed by PK demonstrated superior results in terms of ocular surface stability and graft retention compared with simultaneous LSCT and PK. Limbal stem cells of autologous origin fare better than allogeneic ones in sequential cases.

Amniotic Membrane Biopolymer for Regenerative Medicine

Biopolymers based on the amniotic membrane compare favorably with synthetic materials in that, along with a specific 2D structure, they have biologically active properties. However, in recent years, there has been a tendency to perform decellularization of the biomaterial during the preparation of the scaffold. In this study, we studied the microstructure of 157 samples and identified individual biological components in the manufacture of a medical biopolymer from an amniotic membrane using various methods. Group 1 had 55 samples, and the amniotic membrane was impregnated with glycerol and dried over silica gel. Group 2 had 48 samples, and the decellularized amniotic membrane was impregnated with glycerol followed by lyophilization, Group 3 had 44 samples, and the decellularized amniotic membrane without pre-impregnation with glycerol was subjected to lyophilization. Decellularization was performed by treatment with a low-frequency ultrasound at a frequency of 24-40 kHz in an ultrasonic bath. A morphological study using a light microscope and a scanning electron microscope showed the preservation of the structure of the biomaterial and more complete decellularization in samples subjected to lyophilization without prior impregnation with glycerol. The study of the Raman spectroscopy lines of a biopolymer made from a lyophilized amniotic membrane without preliminary impregnation with glycerin showed significant differences in the intensity of the spectral lines of amides, glycogen, and proline. Additionally, in these samples, the spectral lines of Raman scattering the characteristic of glycerol were not visualized; therefore, only biological substances characteristic of the native amniotic membrane have been preserved.

Ocular-periocular burns in a tertiary hospital: Epidemiologic characteristics

PURPOSE

Ocular burns are ophthalmic emergencies that can cause devastating injuries. This study aimed to analyze the epidemiology, complications, and management of ocular-periocular burns.

METHODS

A total of 193 patients with ocular-periocular burns were admitted to our tertiary hospital from January 2018 to December 2020. The demographic characteristics of the patients, injury variables, complications, and treatments were evaluated.

RESULTS

There were 142 male (73.6%) and 51 female (26.4%) patients with a mean age of 32.53±17.75 years. The average total body surface area was 12% (range, 1-80%). Injuries were most common at work (52.3%) and home (36.3%). Thermal burns were the most common injuries (74.6%), followed by chemical (14.5%) and electrical burns (10.9%). Alkaline agents (75.0%), mainly sodium hydroxide and lime, were common in chemical burns. Superficial lid burns were significantly higher in the thermal group (p < 0.001), and grade III-IV corneal burns were significantly higher in the chemical group (p < 0.001). Various complications were developed in 50 (13%) eyes. Medical treatment only was performed in 318 (82.4%) eyes, and additional surgical treatment was performed in 64 (17.6%) eyes; however, 54 (14.0%) underwent more than one surgery. The most common complications were corneal scars (7.3%), limbal deficiency (4.1%), and ectropion (3.9%). The most frequent procedures performed were amniotic membrane transplantation (AMT) (11.9%) and tarsorrhaphy (6.7%).

CONCLUSION

Chemical burns, limbal and conjunctival ischemia, and full-thickness eyelid defects had a poor prognosis. The degree of limbal deficiency and ınjury of intraocular structures were found to have a great influence on the outcome of their visual acuity.

Outcome of keratolimbal allograft transplantation with deep anterior lamellar keratoplasty for bilateral limbal stem cell deficiency

OBJECTIVES

To evaluate and compare the outcome of keratolimbal allograft (KLAL) transplantation with or without deep anterior lamellar keratoplasty (DALK) for bilateral severe limbal stem cell deficiency (LSCD).

METHODS

This retrospective review included 49 eyes of 46 patients who underwent KLAL transplantation at the Department of Ophthalmology of Chinese PLA general hospital, 2009-2020, for bilateral severe LSCD were examined for corneal clarity and corneal scarring to determine whether to combine DALK with KLAL transplantation. Preoperative information, surgical decision tree, surgical procedures, and postoperative data were collected for each eye.

RESULTS

All patients had preoperative severe or total LSCD. Twenty-four eyes underwent KLAL transplantation only, 25 KLAL transplantation plus DALK. The mean follow-up was 46.80 ± 31.22 months (18-158 months). Overall KLAL survival (with or without DALK) was 71.43% at the final follow-up (KLAL-only 66.67%, KLAL-DALK 76%). Kaplan-Meier survival analysis showed that the 3-year survival probability of all grafts was 70.53 ± 10.89% (KLAL-only 64.86 ± 10.11%, KLAL-DALK 75.79 ± 8.62%). The proportion of BCVA ≥ 20/200 eyes among all KLAL transplantations increased from 11 eyes (22.45%) preoperatively to 25 eyes (51.02%) after 1 year and 24 eyes (48.98%) at the last follow-up (P = 0.01). The proportion of BCVA ≥ 20/200 eyes in the KLAL-DALK group increased significantly (P = 0.04), from 16.0% at baseline to 48.0% after 1 year to 44.0% at the last follow-up. Seventeen eyes (34.69%) had postoperative complications.

CONCLUSION

KLAL-DALK is an effective option to restore a stable ocular surface and visual acuity rapidly in patients with bilateral, late-stage, severe LSCD.

Timing of glaucoma treatment in patients with MICOF: A retrospective clinical study

Purpose

To summarize and discuss the treatment and timing of glaucoma in patients with MICOF keratoprosthesis implantation to guide follow-up clinical treatment.

Methods

The data of 39 eyes (39 patients) with the Moscow Eye Microsurgery Complex in Russia (MICOF) keratoprosthesis implantation in our hospital from 1 January 2002 to 31 December 2017 were collected, including patients with preexisting glaucoma and those who developed glaucoma de novo after MICOF. The sex, age, preoperative diagnosis, glaucoma surgery, keratoplasty, times of keratoplasty, best corrected visual acuity (BCVA) and final follow-up corrected visual acuity, visual field (VF) defect, and cup-to-disk ratio (CDR) were statistically analyzed.

Results

Among 16 eyes with preexisting glaucoma, eight eyes underwent glaucoma surgery before MICOF, 4 eyes underwent glaucoma surgery combined with MICOF, and four eyes were managed medically. Among 23 eyes with de novo glaucoma, seven eyes were treated with surgery and 16 eyes were treated with medication only. A total of 9 (56.3%) eyes had corneal transplants with preexisting glaucoma, which was a higher percentage than that in the patients with de novo glaucoma (n = 5, 21.7%, P = 0.043). In both the preexisting glaucoma group and the de novo glaucoma group, the most common causes were alkali burns (56.3% of preexisting glaucoma and 43.5% of de novo glaucoma). There was no significant difference between the operation and initial visual acuity, postoperative visual acuity, BCVA, CDR, or VF defect. In the de novo glaucoma group, the final follow-up visual acuity of the glaucoma surgery group (1.56 ± 1.07) was worse than that of the mediation group (0.44 ± 0.53) (P < 0.017). Among the complications, the incidence of cornea melting in the patients treated with medications only (n=10) was significantly higher than that in the patients treated with glaucoma surgery (n = 0, P = 0.007), but there was no significant difference in the other complications.

Conclusion

Among patients with MICOF, those patients who have undergone keratoplasty are more likely to develop glaucoma before surgery and glaucoma needs to be prevented. Surgical treatment can be selected according to the ocular surface condition in the patients with de novo glaucoma to reduce the occurrence of complications.

Research models of sulfur mustard- and nitrogen mustard-induced ocular injuries and potential therapeutics

Sulfur mustard (SM) is a notorious, bifunctional alkylating vesicant that was first used in warfare during World War I in 1917 and since then has been deployed in numerous skirmishes with its most recent documented use being during the Middle Eastern conflicts. Apart from its use in combat and terrorist activities, continual threat of accidental exposure from old stockpiles and improperly discarded munitions is ever present, especially to the innocent and unassuming civilian populations. SM can cause devastating injuries, depending on the dosage of SM exposure, route of exposure, as well as the physiological conditions of the individuals exposed. The most common routes of exposure are ocular, dermal, and exposure to the lungs and respiratory tissues through inhalation. Eyes are the most susceptible organ to SM-induced toxicities owing to their high moisture content and rapidly dividing cells. Additionally, ocular injury causes the most expeditious disablement of individuals even upon whole-body exposures. Therefore, it is imperative to understand the mechanisms underlying SM-induced ocular toxicity and design therapeutic interventions to prevent/mitigate ocular injuries. Ocular SM exposure may cause a wide range of symptoms such as inflammation, lacrimation, itching, dryness, photophobia, edema of the cornea/sclera/retina/iris, conjunctivitis, degradation of the corneal layer, fusion of two or more ocular layers, neovascularization, fibrosis, and temporary or permanent structural damage to one or more ocular layers. These symptoms may lead to vision impairments, resulting in partial or complete blindness that may be permanent. The highly toxic and exceedingly notorious nature of SM makes it a highly regulated chemical, requiring very expensive licensing, security, and safety requirements; thus, the more easily accessible analogue, nitrogen mustard (NM) that mimics SM-induced toxicity and injuries is employed in plethora of studies conducted in different animal models and culture systems. This review provides a comprehensive account of the injuries and symptoms that occur upon ocular SM exposures in human patients as well as studies in animal (in vivo, ex vivo) and cell (in vitro) models of SM and NM ocular exposures. Special emphasis has been laid on highlighting the strengths and lacunae in the research as well as the possible unexplored avenues of mechanisms underlying mustard-induced ocular injury that can be explored in future research endeavors. Furthermore, development of therapeutic interventions and targets of interest in the ocular system exposed to SM and NM, based on studies in human patients as well as in vivo, ex vivo, and in vitro models has been discussed in great depth, providing a valuable knowledge database to delineate pathways associated with vesicant-induced toxicity, and strategies/diagnostic tools against SM-induced toxicity.

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.

Ocular Surface Preparation Before Keratoprosthesis Implantation

INTRODUCTION

This study aimed to evaluate the surgical treatment results for conjunctival limbal autograft (CLAU) and keratolimbal allograft (KLAL) in various types of limbal stem cell deficiency (LSCD) etiologies performed in order to achieve a stable ocular surface prior to KPro implantation.

METHODS

We analyzed the outcomes of the surgical treatment of 43 eyes of 39 patients with LSCD as an initial treatment preparing patients' ocular surface for KPro implantation. The most common causes were ocular trauma (50.7%), mainly alkali burns (77%); autoimmune causes, mainly ocular cicatricial pemphigoid (OCP; 17.4%); infection (15.9%) including Lyell's syndrome/Stevens-Johnson syndrome (LS/SJS; 16%). In all 17 eyes operated on with CLAU, this procedure was performed once. Similarly, one uncomplicated KLAL procedure in one eye was performed in 10 women and 19 men. In another one woman and three men, KLAL was performed in both eyes. In one man with Lyell's syndrome, the KLAL operation was performed three times in one eye. Follow-up was at least 12 months.

RESULTS

Visual acuity (VA) improved in 17 eyes (31%) and remained unchanged in 38 eyes (69%). VA improved from light perception to hand movements in three eyes (16%) from the CLAU group of patients and eight eyes (15%) from the KLAL group; VA improved from hand movements to finger counting in two eyes (12%) post CLAU and two eyes (4%) post KLAL operation. The most common complication of surgical treatment was persistent epithelial defect that was refractory to medical treatment in 32 eyes (58%), 5 eyes post CLAU and 27 post KLAL. Corneal conjunctivalization (19%) and neovascularization (29%) were present on the corneal edge of the graft. Symblephara recurred within 3 months in nine eyes (17.3%) after KLAL, including four eyes that had been chemically burned and five eyes with LS/SJS.

DISCUSSION

Pretreatment with CLAU or KLAL procedures in severely damaged ocular surfaces allows the ocular surface to be prepared for safe KPro implantation with sufficient tissue surroundings with less conjunctivalization and deeper conjunctival fornices.

Various administration forms of decellularized amniotic membrane extract towards improving corneal repair

Amniotic membrane (AM) transplantation is often used as a treatment for corneal repair, but AM is prone to dissolving and shedding after surgery; multiple transplants will cause pain and financial burden. In this work, human amniotic membrane was firstly decellularized to obtain an AM extracellular matrix (dAM). This dAM was homogenized and extracted to obtain the dAM extract (simplified as dAME). Different forms of administration for corneal injury were performed as liquid drops (diluted dAME), in situ gels (using temperature-dependent Poloxamer 407 as the matrix), and tablets (poly(vinyl alcohol) as the matrix). The cytocompatibility of dAME was evaluated using corneal epithelial cells, corneal stromal cells and fibroblasts as cell models. The results showed that dAME is biocompatible to all these cells. Cells exhibited normal morphology and growth state at a dAME concentration of up to 160 μg mL^-1. In vivo, dAME exhibited increased wound healing efficiency in severe corneal injury, being characterized with a shorter healing time for epithelium and a faster recovery for stromal opacity and thickness, compared with those of the control eyes. Different forms of administration have different effects on corneal repair; among them, in situ gels achieved the best therapeutic efficiency. Their biological mechanism was detected via quantitative real-time polymerase chain reaction (qRT-PCR) technology. It was confirmed that dAME plays important roles in promoting the mRNA expression of leucine-rich and immunoglobulin-like domains 1 (LRIG1) and in inhibiting the mRNA of transforming growth factor-β1 (TGF-β1).

Long-Term Outcome After Superficial Keratectomy of the Abnormal Epithelium for Partial Limbal Stem Cell Deficiency

PURPOSE

To investigate the etiology and long-term surgical prognosis of the abnormal epithelium for partial limbal stem cell deficiency (LSCD), following superficial keratectomy DESIGN: Retrospective, interventional case series METHODS: This single-center, retrospective study was conducted to assess the prognosis of consecutive patients who underwent superficial keratectomy, with or without amniotic membrane transplantation (AMT), for the treatment of partial LSCD, from 2010 to 2019. We analyzed the etiologies of partial LSCD, surgical success rate, prognosis for recurrent cases, and the improvement in visual acuity.

RESULTS

We included 40 patients (51 eyes) with partial LSCD. All eyes were in clinical stage II without dense fibrovascular tissue. Idiopathy was the most common etiology (39%), followed by multiple surgeries involving the corneoscleral limbus (19%). All eyes attained corneal reepithelialization and transparency. Furthermore, the visual acuity improved or remained unchanged postoperatively. We observed recurrence in 19 eyes (37%) with a mean follow-up period of 26.3 months. Despite no significant difference in the recurrence rates among different etiologies, postoperative delayed epithelialization and extensive limbal involvement were identified as risk factors for recurrence (P < .001 and P = .013, respectively). Repeat surgeries were performed in 16 eyes. The final success rate was 84%.

CONCLUSIONS

Superficial keratectomy is useful for the treatment of partial LSCD of varied etiologies, with an expected improvement in visual acuity postoperatively. Although the procedure can be repeated and have a high success rate, there have been several cases of recurrence in the long-term postoperative course.

Ocular toxicity of mustard gas: A concise review

Sulfur mustard (SM) is a chemical warfare agent that has been used throughout recent history and remains a threat today. Exposed soldiers and civilians experience a variety of symptoms primarily in the respiratory system, skin, and eyes. The ocular tissues are highly sensitive to damage by SM and undergo unique manifestations of acute, chronic, and delayed complications that can persist for months and years after exposure. The mechanisms of this unique mustard gas keratopathy are still not fully understood and animal models for the study of this disease are discussed. Recent advances in mechanisms of injury are included in this review. Ophthalmic manifestations of SM injury including persistent epithelial defects, limbal stem cell deficiency, corneal neovascularization, dry eye, and corneal opacification have been reported. A wide variety of medical and surgical therapies have been studied and are reviewed here along with potential future therapies.

Understanding cornea epithelial stem cells and stem cell deficiency: Lessons learned using vertebrate model systems

Animal models have contributed greatly to our understanding of human diseases. Here, we focus on cornea epithelial stem cell (CESC) deficiency (commonly called limbal stem cell deficiency, LSCD). Corneal development, homeostasis and wound healing are supported by specific stem cells, that include the CESCs. Damage to or loss of these cells results in blindness and other debilitating ocular conditions. Here we describe the contributions from several vertebrate models toward understanding CESCs and LSCD treatments. These include both mammalian models, as well as two aquatic models, Zebrafish and the amphibian, Xenopus. Pioneering developments have been made using stem cell transplants to restore normal vision in patients with LSCD, but questions still remain about the basic biology of CESCs, including their precise cell lineages and behavior in the cornea. We describe various cell lineage tracing studies to follow their patterns of division, and the fates of their progeny during development, homeostasis, and wound healing. In addition, we present some preliminary results using the Xenopus model system. Ultimately, a more thorough understanding of these cornea cells will advance our knowledge of stem cell biology and lead to better cornea disease therapeutics.

Outcomes of Limbal Stem Cell Transplant: A Meta-analysis

Importance

Limbal stem cell transplant (LSCT) can be categorized as direct autologous limbal transplant (AULT), direct allogenic limbal transplant (ALLT), cultivated autologous limbal stem cells transplant (cAULT), and cultivated allogenic limbal stem cells transplant (cALLT). To our knowledge, there is no study directly comparing the outcomes and complications of these procedures.

Objective

To evaluate the outcomes of different LSCT procedures.

Data Source

We searched PubMed, EMBASE, Web of Science, and Cochrane without language filter for peer-reviewed articles about LSCT. The latest search was performed on June 30, 2019.

Study Selection

Clinical studies with the outcome of at least 20 eyes after LSCT were included. Animal studies and studies of other surgical interventions were excluded.

Data Extraction and Synthesis

Two reviewers independently abstracted the data from each study. Heterogeneity was evaluated with the I2 statistic, and a meta-analysis was performed using the random-effects model.

Main Outcomes and Measures

Outcome measures included the improvement of ocular surface, visual acuity (VA), and adverse events of recipient eyes and donor eyes.

Results

Forty studies (2202 eyes) with a mean (SD) follow-up of 31.3 (20.9) months met the inclusion criteria. The mean (SD) age of study participants was 38.4 (13.1) years, and men accounted for 74%. The number of eyes that underwent AULT, ALLT, cAULT, and cALLT were 505, 742, 771, and 184, respectively. Improvement of the ocular surface was achieved in 74.5% of all eyes, 85.7% of eyes after AULT (95% CI, 79.5%-90.3%), 84.7% after cAULT (95% CI, 77.2%-90.0%), 57.8% after ALLT (95% CI, 49.0%-66.1%), and 63.2% after cALLT (95% CI, 49.3%-75.2%). Autologous limbal transplantation resulted in a greater VA improvement rate (76%) than did the other 3 procedures (cAULT: 56.4%; ALLT: 52.3%; cALLT: 43.3%; all P < .001). The most common adverse events in all recipient eyes were recurrent/persistent epithelial erosion (10.5%; 95% CI, 7.2%-23.3%) and elevated intraocular pressure (intraocular pressure, 1.7%; 95% CI, 0.5%-7.8%). Patients who underwent ALLT had the highest rate of recurrent epithelial erosion (27.8%; 95% CI, 17.1%-41.9%) and intraocular pressure elevation (6.3%; 95% CI, 1.8%-19.4%).

Conclusions and Relevance

These findings suggest LSCT can improve or stabilize the corneal surface with a low rate of severe ocular complications and that autologous LSCT may have a higher success rate and fewer complications than allogenic LSCT.

The Surgical Outcomes of Limbal Allograft Transplantation in Eyes Having Limbal Stem Cell Deficiency

Purpose:

To report the limbal allograft transplantation and penetrating keratoplasty (PK) results in limbal stem cell deficiency (LSCD)-developed eyes because of chemical or thermal injury.

Methods:

Medical records of 18 eyes of 14 patients who had undergone keratolimbal allograft (KLAL) or living-related conjunctival limbal allograft (lr-CLAL) with or without PK and followed up at least 1 year postoperatively were evaluated retrospectively. The preoperative LSCD grade was noted in all patients. Rejection incidents, recurrence of LSCD, and corneal graft clarity along with a visual improvement during the follow-up were noted. The complications rate due to surgery or injury itself, for instance, glaucoma and cataract, were evaluated. The limbal allograft tissue survival analysis and corneal allograft survival analysis were done to reveal the differences in both the procedures. The existence of normal corneal epithelium and improvement in visual acuity were accepted as the surgical success criteria.

Results:

In the limbal allograft transplantation group, the survival rates of the allograft tissue were 65 ± 10.7% at 1 year and 36.6 ± 11.4% at 3 years in lr-CLAL and 66.7 ± 15.7% at 12 months and 53.3 ± 17.3% at 18 months in KLAL-transplanted eyes. The survival rate of corneal allograft at the 5^th postoperative year was lower in the simultaneous procedure compared to the staged procedure, but it was not statistically significant (25.7 ± 25.8% vs. 62.5 ± 17.1%, P = 0.75). The ambulatory vision was achieved in 10 eyes (56%) after a mean follow-up time of 93.8 ± 37.8 months. The visual acuity level has increased in 12 eyes (67%) in which the limbal allograft transplantation was applied. The ambulatory visual acuity level was achieved (≤1.0 logMar [20/200]) in 10 eyes (56%). In addition, two or more Snellen lines’ gain in the best corrected visual acuity was observed in 12 eyes of 18 (67%) at the last follow-up, and there was not any significant difference between the KLAL and lr-CLAL.

Conclusions:

Ocular surface integrity was longer in KLAL than in lr-CLAL transplantation, but it was not statistically significant. The staged procedure was more convenient than the simultaneous procedure in terms of corneal allograft clarity maintenance in limbal allograft-employed eyes.

Long-Term Outcomes of Allogeneic Ocular Surface Reconstruction: Keratolimbal Allograft (KLAL) Followed by Penetrating Keratoplasty (PK)

Purpose

Long-term results of the patients with total LSCD, who had undergone keratolimbal allograft (KLAL) for limbal reconstruction followed by penetrating keratoplasty (PK).

Methods

The study analyzes surgical treatment of 43 eyes with severe ocular surface disorders. All subjects underwent KLAL to achieve suitable conditions for consecutive PK. Due to failures of primary treatment in 17 eyes (39%), the KLAL was repeated. PK was performed in all the patients at 9-12 months after KLAL. As a retrospective study we analyzed data from the medical records including the preoperative and postoperative best corrected visual acuity, corneal clarity, surgical outcomes and complications, postoperative intraocular pressure, graft rejection, and other comorbidities and complications.

Results

The preoperative visual acuity ranged from light perception to 0.01. The final improvement of visual acuity within a gain of one or more lines with the Snellen chart, including the results of successive surgical treatments after PK, was achieved in 23 operated eyes (53%). Early graft rejection was observed in 4 eyes (9%). In 3 eyes, it was manifested as endothelial rejection, and in 1 eye, as combined endothelial and epithelial rejection. PK failure requiring repetitive PK was present in 14 eyes (32%). Phthisis bulbi developed in 6 eyes (14%). Glaucoma or ocular hypertension was reported in 25 eyes (58%). A majority were treated with up to 3 topical agents or referred for trabeculectomy in 3 cases, transscleral cyclophotocoagulation in 2 eyes, and EX-PRESS glaucoma shunt implantation in 3 cases.

Conclusions

Successful KLAL carries a high risk of subsequent PK failure. Visual function remains the second aim of treatment; the primary one is to stabilize the surface.

Allogenic simple limbal epithelial transplantation (alloSLET) from cadaveric donor eyes in patients with persistent corneal epithelial defects

BACKGROUND/AIM

To describe the clinical outcome of allogenic simple limbal epithelial transplantation (alloSLET) utilising tissue from cadaveric donor eyes after failed re-epithelialisation of the corneal surface.

METHODS

Medical records of 14 eyes from 14 patients treated for persistent corneal epithelial defects with alloSLET were reviewed. The primary outcome measure was complete epithelialisation of the corneal surface. Secondary outcome measures were best corrected visual acuity (BCVA) and postoperative side effects due to surgery or medical therapy.

RESULTS

Of the 14 eyes, 7 received alloSLET only and 7 alloSLET together with penetrating keratoplasty (PK). Thirteen (92.9%) of 14 eyes had an epithelialised corneal surface 3 and 6 months after surgery and 10 (71.4%) of 14 eyes displayed an epithelialised corneal surface 12 months after surgery. In both subgroups, alloSLET only and alloSLET with PK, respectively, 5 (71.4%) of 7 eyes had a stable corneal epithelium 12 months after surgery, respectively. Postoperatively, BCVA improved markedly in the whole patient collective. However, the increase was not significant when looking at the two individual subgroups. One patient lost his bandage contact lens several times within the first postoperative month and had a partial detachment of the amniotic membrane. The ocular surface of this patient failed to epithelialise. In three patients, limbal donor pieces translocated to the centre of the cornea, which possibly prolonged the improvement of BCVA.

CONCLUSION

AlloSLET appears to be an effective treatment option in eyes with non-healing corneal epithelial defects when autologous limbal tissue is not available.

The long-term surgical outcomes of conjunctival-limbal autograft procedure with or without penetrating keratoplasty in eyes with unilateral limbal stem cell deficiency

AIM:

The aim of the study is to report the results of conjunctival-limbal autograft (CLAU) transplantation and penetrating keratoplasty (PK) in eyes with limbal stem cell deficiency (LSCD) due to chemical or thermal injury.

METHODS:

Thirty-one eyes of the 31 patients, who had unilateral LSCD due to chemical or thermal injury, were included in the study. Bilaterally affected cases and LSCD due to Steven-Johnson syndrome and mucous membrane pemphigoid were excluded from the study. All patients underwent a complete ophthalmologic examination. The surgical procedures, postoperative complications, ocular surface status, and visual outcomes were noted.

RESULTS:

In the CLAU group, regular corneal epithelium and ambulatory vision (≤1.0 logarithm of the minimum angle of resolution [20/200]) were achieved in 81% of eyes, including 22 eyes (71%) that were assessed after a mean follow-up period of 58 months, respectively. The 5-year survival rate of corneal allograft was 33%, 4 ± 13.9 in the CLAU applied eyes. In addition, the corneal graft clarity maintenance rate was found to be higher in patients having ≥12 months duration between CLAU and PK, which is statistically significant (62% vs. 23%, P = 0.046).

CONCLUSION:

Waiting at least 1 year after CLAU transplantation to perform PK increases corneal clarity. Eyelid problems, even if the eyelids were reconstructed properly, remain a major risk factor for the development of the epithelial disorder in the early and late postoperative period in CLAU applied eyes.

Autologous limbal stem cell transplantation: a systematic review of clinical outcomes with different surgical techniques

PURPOSE

To conduct a systematic review on outcomes of three different techniques of autologous limbal stem cell transplantation (LSCT): conjunctival-limbal autografting (CLAu), cultivated limbal epithelial transplantation (CLET) and simple limbal epithelial transplantation (SLET), in unilateral limbal stem cell deficiency (LSCD).

METHODS

Literature searches were conducted in MEDLINE (Ovid), Embase, Web of Science and Cochrane Central Register. Standard systematic review methodology was followed using Meta-analysis of Observational Studies in Epidemiology guidelines. Studies with a sample size of more than 10 eyes were included. The primary outcome measure of efficacy was restoration of a completely epithelised, stable and avascular corneal surface (anatomical success). The secondary outcome measure of efficacy was improvement in best-corrected visual acuity of two-lines or greater (functional success).

RESULTS

The review identified 22 non-comparative case series, which included 1023 eyes. Ocular burns were the major (88%) indication for surgery. Overall, at a median postoperative follow-up of 1.75 years, autologous LSCT for unilateral LSCD showed anatomical and functional success rates of 69% and 60%, respectively, without any serious adverse events in the donor eye. The follow-up duration and indications for surgery were comparable across all groups (p>0.05). The anatomical and functional success rates of SLET (78%; 68.6%) and CLAu (81%; 74.4%) were comparable, and significantly better than those of CLET (61.4%; 53%; p=0.0048).

CONCLUSION

Autologous LSCT is a safe and effective treatment for unilateral LSCD. In the absence of randomised controlled trials, existing evidence clearly suggests that clinical outcomes are better with SLET and CLAu as compared with CLET.

Comparison of the efficacy of different cell sources for transplantation in total limbal stem cell deficiency

PURPOSE

The purpose of this study was to compare the efficacy of allogeneic cultured limbal epithelial transplantation (ACLET) and cultivated oral mucosal epithelial transplantation (COMET) in treating total limbal stem cell deficiency (LSCD).

METHODS

In this retrospective cohort study, 73 patients (76 eyes) with total LSCD, including 41 patients (42 eyes) treated with ACLET and 32 patients (34 eyes) receiving COMET, were evaluated. The age, gender and injury cause of all patients were recorded.

RESULTS

The mean follow-up was 23.3 ± 9.9 months in the ACLET group and 16.1 ± 5.8 months in the COMET group. A higher incidence of persistent epithelial defect was observed after COMET (P = 0.023). The overall ocular surface grading scores were all lower in the ACLET group than in the COMET group at 3, 6, and 12 months after surgery and the last follow-up. Kaplan-Meier survival curve analysis demonstrated a significantly higher success rate of ACLET (71.4%), compared with that of COMET (52.9%; P = 0.043). The risk of graft failure was higher in patients with entropion and trichiasis, incomplete eyelid closure and treated with COMET. The graft failure risk rate after COMET was 3.5 times higher than that of ACLET.

CONCLUSIONS

For total LSCD patients, ACLET should be prioritized, since limbal epithelial cells have better ability to maintain corneal epithelial integrity and ocular surface stability and benefit the ocular surface when compared with oral mucosal epithelial cells. Preoperative and postoperative eyelid abnormalities should be corrected as early as possible.

The application of human amniotic membrane in the surgical management of limbal stem cell deficiency

The application of human amniotic membrane (AM) has a wide spectrum of indications in the treatment of ocular surface disorders. Transplantation of AM has been incorporated routinely as a component of ocular surface reconstruction in a variety of ocular pathologies. The application of human AM can be combined with nearly all types of limbal transplantation in treating limbal stem cell deficiency (LSCD). AM provides support and possible protection to the transplanted limbal tissues and limbal stem cells owing to its mechanical and biological properties, and these properties are thought to enhance the success rate of LSC transplantation. This paper reviews the current literature on the applications of AM in the surgical management of LSCD and summarizes the outcome of different surgical approaches. The current literature contains mostly low-level evidences in supporting the role of AM. The efficacy of AM in LSC transplantation needs to be confirmed by randomized controlled clinical trials.

Repairing the corneal epithelium using limbal stem cells or alternative cell-based therapies

INTRODUCTION

The corneal epithelium is maintained by limbal stem cells (LSCs) that reside in the basal epithelial layer of the tissue surrounding the cornea termed the limbus. Loss of LSCs results in limbal stem cell deficiency (LSCD) that can cause severe visual impairment. Patients with partial LSCD may respond to conservative therapies designed to rehabilitate the remaining LSCs. However, if these conservative approaches fail or, if complete loss of LSCs occurs, transplantation of LSCs or their alternatives is the only option. While a number of clinical studies utilizing diverse surgical and cell culture techniques have shown favorable results, a universal cure for LSCD is still not available. Knowledge of the potential risks and benefits of current approaches, and development of new technologies, is essential for further improvement of LSCD therapies.

AREAS COVERED

This review focuses on cell-based LSCD treatment approaches ranging from current available clinical therapies to preclinical studies of novel promising applications.

EXPERT OPINION

Improved understanding of LSC identity and development of LSC expansion methods will influence the evolution of successful LSCD therapies. Ultimately, future controlled clinical studies enabling direct comparison of the diverse employed approaches will help to identify the most effective treatment strategies.

Surgical management of severe ocular surface injury due to Roman candle explosion accidents

PURPOSE

To report the clinical features, management, and outcomes of patients with ocular surface damage secondary to Roman candle explosion accidents.

METHODS

Retrospective, noncomparative, interventional case series of 11 patients with Roman candle explosion-related ocular surface injuries referred to the Cincinnati Eye Institute between 2007 and 2016.

RESULTS

Eleven patients (10 male, 1 female, mean age 22.4 years) sustained unilateral ocular surface injuries with presenting visual acuity ranging from count fingers to light perception. All patients had severe limbal stem cell deficiency with total ocular surface failure. Eight eyes received a conjunctival-limbal autograft (CLAU) with a keratolimbal allograft (KLAL), 1 eye received a living related-conjunctival limbal allograft (lr-CLAL) with a KLAL, and 2 eyes received a CLAU with lr-CLAL. Nine eyes underwent subsequent penetrating keratoplasty, and 7 eyes had reconstructive eyelid surgery. Nine eyes demonstrated improved visual acuity at last follow-up; seven eyes demonstrated a stable ocular surface at last follow-up. Nonadherence was noted in 7 patients, either with poor adherence with post-operative treatment or poor follow-up; this portended a worse visual result.

CONCLUSIONS

Roman candle-related accidents can lead to severe ocular surface injury. Despite total ocular surface failure, these eyes can achieve good postoperative visual results following limbal stem cell transplantation and subsequent keratoplasty with appropriate compliance.

Systemic immunosuppression in limbal stem cell transplantation: best practices and future challenges

The objective of this study was to evaluate systemic immunosuppression regimens used for patients undergoing ocular surface stem cell transplantation, including their benefits and adverse effects in the adjunctive management of limbal stem cell deficiency (LSCD). A systematic literature review was conducted using the MEDLINE and EMBASE databases (1980-2015). Data were collected on surgical intervention(s), type of immunosuppressive agent(s), duration of immunosuppression, percentage with stable ocular surface at last follow-up, mean follow-up time, and demographics. Data were also collected on adverse ocular and systemic outcomes. Sixteen reports met the inclusion criteria. There were no randomized controlled studies. Three studies were noncomparative prospective case series, whereas the majority were retrospective case series. Bilateral severe LSCD was the most common disease (50%), and keratolimbal allograft was the most common intervention (80%). Immunosuppressive regimens showed a progression from early studies using oral cyclosporine to later studies using combinations of mycophenolate mofetil and tacrolimus. Most studies included a course of high-dose systemic corticosteroids. For patients adherent to long-term systemic immunosuppression, stable ocular surface rates of 70%-80% at last follow-up were reported. Adverse effects included hypertension, diabetes mellitus, and biochemical abnormalities managed with pharmacotherapy or discontinuation of offending agents. There were no cases of mortality related to immunosuppression. However, the current literature does not elucidate which immunosuppressive regimen is most efficacious for different categories of LSCD or graft types. Evidence-based guidelines for systemic immunosuppression in limbal allograft therapy would benefit from randomized controlled and/or additional prospective studies. Long-term immunosuppression would benefit from close collaboration between ophthalmologists and transplant specialists to individualize treatments.

Limbal Stem Cell Transplantation and Complications

Corneal epithelial stem cells are adult somatic stem cells located at the limbus and represent the ultimate source of transparent corneal epithelium. When these limbal stem cells become dysfunctional or deficient, limbal stem cell deficiency (LSCD) develops. LSCD is a major cause of corneal scarring and is particularly prevalent in chemical and thermal burns of the ocular surface. LSCD leads to conjunctivalization of the corneal surface, neovascularization, recurrent or persistent epithelial defects, ocular surface inflammation, and scarring that, in turn, lead to decreased vision, pain, and impaired quality of life. Several techniques have been reported for limbal stem cell transplantation (LSCT). We introduce the surgical techniques, examine the success rate, and discuss the postoperative complications of conjunctival limbal autograft (CLAU), cultivated limbal stem cell transplantation (CLET), simple limbal epithelial transplantation (SLET), and limbal allograft, including keratolimbal allografts (KLAL) and living-related conjunctival allograft (LR-CLAL).

Keratolimbal allograft for limbal stem cell deficiency after severe corneal chemical injury: a systematic review

Purpose

To review the published literature on outcomes of keratolimbal allograft (KLAL) for the surgical treatment of limbal stem cell deficiency (LSCD) and corneal blindness after severe corneal chemical injury.

Methods

Literature searches were conducted in the following electronic databases: MEDLINE, EMBASE, Science Citation Index, CINAHL, LILACS and the Cochrane Library. Standard systematic review methodology was applied. The main outcome measure was the proportion of eyes with best-corrected visual acuity (BCVA) ≥20/200 at last follow-up. Other measures of allograft success were also collected.

Results

We identified six reports in which KLAL outcomes in the eyes after chemical injury could be distinguished. There were no randomised controlled studies. The outcomes of KLAL in 36 eyes of 33 patients were analysed. One study with seven eyes did not specify KLAL follow-up specific to chemical injury. Median postoperative follow-up for the other 29 eyes in 26 patients was 42 months (range 6.2–114 months). In the same 29 eyes, 69% (20/29) had BCVA ≥20/200 at the last follow-up examination. Eighty-nine per cent of all eyes (32/36) underwent penetrating keratoplasty simultaneous or subsequent to KLAL.

Conclusions

The number of studies where outcomes of KLAL in eyes with severe corneal chemical injury could be discerned was limited, and variability was observed in outcome reporting. The quality of evidence to support the use of KLAL in LSCD in severe chemical corneal burns was low. Standardisation and longer follow-up are needed to better define evidence-based best practice when contemplating surgical intervention for blindness after corneal chemical injury.

PROSPERO registration number

CRD42017054733.

Conjunctival-limbal autograft

PURPOSE OF REVIEW

To provide an overview of conjunctival-limbal autografting (CLAU) for ocular surface rehabilitation with emphasis on more recent literature detailing outcomes of the procedure over the last 2 decades as well as technique variations and adjuvant techniques.

RECENT FINDINGS

Limbal autografting initially described in 1964 by Barraquer and Strampelli and later popularized by Kenyon and Tseng is considered the best option for restoration of corneal phenotype in unilateral limbal stem-cell deficiency. Although there have been developments in alternative limbal epithelial stem-cell techniques including ex-vivo tissue engineering methods, because of the benefit of immunohistocompatability, this procedure still provides better long-term outcomes. As autograft donor tissue is valuable, optimization of the recipient eye preoperatively with good lid closure and reduction of inflammation is vital for success as is close postoperative follow-up. Variations in the technique described have included the modified Cincinnati technique combining CLAU with cadaveric keratolimbal allograft to avoid conjunctivalization. In addition, simple limbal epithelial autograft transplantation, a less-invasive technique combined with amniotic membrane transplantation, has shown promise.

SUMMARY

In spite of the development of new epithelial transplant techniques, in unilateral limbal stem-cell deficiency, CLAU from a healthy unaffected fellow eye remains the best option available for restoration of corneal phenotype.

Diagnostic criteria for limbal stem cell deficiency-a systematic literature review

The diagnosis of limbal stem cell deficiency (LSCD) is often based on clinical manifestations with or without the use of tests to demonstrate the presence of goblet cells or of specific epithelial markers on the corneolimbal surface. This systematic review looks at the various diagnostic methods used in the diagnosis of LSCD in published interventional studies. The design is a systematic literature review. We did a systematic search on MEDLINE and PUBMED for articles published in English between January 1, 2003, and December 31, 2013. We collected data on diagnostic methods used to diagnose LSCD (clinical findings, impression cytology, immunohistochemistry for various epithelial markers, or in vivo confocal microscopy). Forty-six studies (mostly retrospective/interventional case series) met the inclusion criteria. All of the studies used clinical features as evidence of LSCD: discomfort, impaired vision, irregular epithelium, unstable tear film, persistent epithelial defects, scarring, fibrovascular pannus, neovascularization, keratinization, calcification, and opacification of the cornea. Eighteen studies (39.1%) used an additional test for the diagnosis; 17 studies (37.0%) used impression cytology for goblet cells, 4 studies (8.7%) used immunohistochemistry for epithelial markers, and 2 studies (4.3%) use in vivo confocal microscopy. The diagnosis of LSCD was made in most cases on clinical grounds alone. In some studies, diagnostic tests were used, but these varied considerably from study to study. Comparison of effectiveness of various interventions requires standardized diagnostic methods. Consensus on the diagnostic criteria for LSCD is essential and needs to be reached by the interested care providers.

Clinical Spectrum and Treatment Approaches in Corneal Burns

Objectives:

To evaluate the clinical findings, treatment modalities and long-term prognosis of chemical and thermal burns of the cornea.

Materials and Methods:

Twenty-one patients (27 eyes) who were followed at two centers for corneal chemical and thermal burns between 2001 and 2013 were included. Eyes were grouped into four grades according to the severity of burn using Roper-Hall classification. Age, gender, type of burn, follow-up duration, corrected visual acuity before and after treatment, treatment modalities and complications were recorded. Patients received medical treatment or combined surgical treatment including amniotic membrane transplantation (AMT), conjunctivolimbal autograft/allograft (CLAU/CLAL) transplantation, keratolimbal allograft (KLAL) or penetrating keratoplasty (PKP).

Results:

Patients had a mean age of 27.1±15.5 years (range, 6 months-56 years) and were followed for a mean 63.2±58.6 weeks (4-160 weeks). Significant improvement was achieved with medical treatment alone in patients with grade I (4 eyes) and 2 burns (8 eyes). Patients with grade III burns (11 eyes) underwent CLAU (6 eyes), combined AMT/CLAU (3 eyes), AMT/CLAL (1 eye), or CLAL+PKP (1 eye), while patients with grade IV burns (4 eyes) had keratectomy+CLAL/AMT (1 eye), keratectomy+CLAL+PKP after recurrence with CLAU/AMT (1 eye), CLAU+PKP (1 eye), and AMT/KLAL+PKP (1 eye). All patients except the latter showed ocular surface stabilization with these procedures.

Conclusion:

Ocular burns cause severe impairment of the ocular surface. It is possible to achieve good results with appropriate medical treatment and surgeries including ocular surface reconstruction.

Coculture of autologous limbal and conjunctival epithelial cells to treat severe ocular surface disorders: long-term survival analysis

BACKGROUND

Cultivated limbal epithelium for reconstruction of corneal surface is a well-established procedure; however, it is not adequate for damage which also extensively involves the conjunctiva. In severe cases of ocular surface damage that warrant additional conjunctival transplantation apart from cultivated limbal stem cell transplantation, we describe the long-term survival of a novel method of cocultivating autologous limbal and conjunctival epithelium on a single substrate.

MATERIALS AND METHODS

Forty eyes of 39 patients with severe limbal stem cell deficiency and conjunctival scarring or symblepharon underwent transplantation of autologous cocultivated epithelium on human amniotic membrane. A ring barrier was used to segregate the central limbal and peripheral conjunctival epithelia in vitro. Patients were followed up at regular intervals to assess stability of the ocular surface, defined by absence of conjunctivalization into the central 4 mm of the cornea and absence of diffuse fluorescein staining. Penetrating keratoplasty (PKP) was subsequently performed, where indicated, in patients with surface stability.

RESULTS

The cumulative survival probability was 60% at 1 year and 45% at 4 years by Kaplan-Meier analysis (mean follow-up duration: 33 ± 29 months, range: 1-87 months). Best-corrected visual acuity improved to greater than 20/200 in 38% eyes at the last follow-up, compared with 5% eyes before surgery. Immunohistochemistry in five of the corneal buttons excised for PKP showed an epithelial phenotype similar to cornea in all five.

CONCLUSIONS

Synchronous use of cultured limbal and conjunctival epithelium offers a feasible alternative and a simpler one-step surgical approach to treat severe ocular surface disorders involving limbus and conjunctiva.

Ocular surface reconstruction after exposure to high concentrations of antiseptic solutions

PURPOSE

To report the clinical course in accidental exposure of the cornea to antiseptic solutions in 3 cases.

METHODS

Observational case series. Exposure to 20% chlorhexidine gluconate solution was observed in 2 cases and to 10% benzalkonium chloride solution in 1 case.

RESULTS

Not only superficial damage but also toxicity to corneal endothelial cells leading to corneal edema was observed in all 3 cases. Epithelial transplantation was performed: autologous cultivated limbal epithelial transplantation (auto-CLET), conjunctivolimbal autograft (CLAU), or living-related cultivated limbal epithelial transplantation (lr-CLET). A stable ocular surface was achieved, although exposure to high concentrations of antiseptic solutions caused severe anterior chamber inflammation; cataract and glaucoma developed in 2 cases, requiring further surgical treatment.

CONCLUSIONS

Exposure to high concentrations of antiseptics causes both ocular surface and intraocular damage. Epithelial transplantation enables restoration of a stable ocular surface. However, management of intraocular consequences, including secondary glaucoma and corneal endothelial damage, still remains a challenge in the prognosis of such cases.

Long-term outcome of cultivated oral mucosal epithelial sheet transplantation in treatment of total limbal stem cell deficiency

PURPOSE

To evaluate the long-term outcome of cultivated oral mucosal epithelial transplantation (COMET) in treatment of eyes with total limbal stem cell deficiency.

DESIGN

Noncomparative, retrospective, interventional case series.

PARTICIPANTS

Forty eyes in 36 patients with total limbal stem cell deficiency (Stevens-Johnson syndrome in 12 eyes, chemical or thermal burns in 11 eyes, ocular cicatricial pemphigoid [OCP] in 9 eyes, pseudo-OCP in 7 eyes, and gelatinous drop-like dystrophy in 1 eye) were treated at the Department of Ophthalmology, Tokyo Dental College, Chiba, Japan.

INTERVENTION

Cultivated autologous oral mucosal epithelial sheets were transplanted onto the ocular surface in eyes with total limbal stem cell deficiency.

MAIN OUTCOME MEASURES

Reconstruction of a stable ocular surface with a clear appearance and no epithelial defects, reduction in fibrovascular tissue invasion of corneal surface, a functional fornix, change in visual acuity, and postoperative complications.

RESULTS

The mean follow-up period was 25.5 months (range, 6-54.9 months). Kaplan-Meier analysis of a corneal surface stability revealed an early decline in transplanted oral mucosal epithelial stability over the first 6 months, remaining comparatively stable thereafter (1 year, 64.8%; 2 years, 59.0%; and 3 years, 53.1%). Postoperative persistent epithelial failure developed within the first 3 months in 9 eyes. Early epithelial failure was associated closely with preoperative corneal defects. Gradual fibrovascular tissue invasion of the corneal surface was observed in 8 eyes and was marked in cases of OCP. Survival of a functional fornix decreased progressively until approximately 6 months. Postoperative visual acuity seemed to be related to the presence of corneal opacity. Complications included stromal melting or perforation in 8 eyes, infectious keratitis in 2 eyes, glaucoma in 8 eyes, and recurrence of herpetic keratitis in 1 eye. Corneal melting or perforation and infectious keratitis were associated closely with persistent epithelial defects after COMET.

CONCLUSIONS

The transplantation of cultivated oral mucosal epithelial sheets offers a viable and safe alternative in the reconstruction of a stable ocular surface. Epithelialization of the corneal surface is very important not only in obtaining a satisfactory long-term outcome, but also in achieving a lower incidence of complications.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

A new surgical technique: a femtosecond laser-assisted keratolimbal allograft procedure

PURPOSE

To evaluate the feasibility of a femtosecond (FS) laser-assisted keratolimbal allograft (KLAL) technique.

DESIGN

Interventional case series.

METHODS

This study included 3 patients with extensive limbal stem cell deficiency. The donor cornea was dissected with an FS laser (IntraLase FS laser, 60 kHz) using a ring procedure, without outer side cutting for the limbal graft, after a penetrated dissection of the donor cornea prior to penetrating keratoplasty (PKP). The depth and width of the ring procedure were adjusted for each individual patient. Further extension to the periphery of the sclerocorneal tissue of the donor graft was performed with a diamond knife. In a case of KLAL alone, the unhealthy limbal tissue of the recipient was removed with the FS laser by the same method employed in donor preparation. One patient underwent KLAL alone, and 2 patients underwent KLAL combined with PKP. The patients were followed up for a maximum of 10 months.

RESULTS

Limbal grafts were even and thin, as expected. The case with KLAL alone showed the fastest epithelization of the recipient cornea. The 2 cases of combined KLAL and PKP showed excellent approximation between recipient and donor tissue. The ocular surfaces have been stable for 8 months in case 1 and 10 months in cases 2 and 3.

CONCLUSION

FS laser-assisted KLAL has potential advantages in terms of simplicity and speed as compared with conventional techniques.

[Ocular burns]

Ocular or thermal burns account for 7.7%-18% of ocular trauma. The majority of victims are young. The burns occur in the setting of accidents at work or in the home, or during a physical attack. Chemical burns by strong acids or bases are responsible for the most serious injuries. Associated with the destruction of limbal stem cells, they present as recurrent epithelial ulcerations, chronic stromal ulcers, deep stromal revascularization, conjunctival overlap, or even corneal perforation. The initial clinical exam is sometimes difficult to perform in the presence of burning symptoms. Nevertheless, it enables the physician to classify the injury, establish a prognosis, and most importantly, guide the therapeutic management. The Roper-Hall modification of the Hughes classification system is the most widely utilized, broken down into stages based on the size of the stromal opacity and the extent of possible limbal ischemia. This classification is now favorably supplemented by those proposed by Dua and Wagoner, which are based on the extent of the limbal stem cell deficiency. The prognosis of the more serious forms of ocular burns has markedly improved over the last decade because of a better understanding of the physiology of the corneal epithelium. Surgical techniques aimed at restoring the destroyed limbal stem cells have altered the prognosis of severe corneal burns. In order to decrease the incidence of burns, prevention, particularly in industry, is essential.