Simple Limbal Epithelial Transplantation

Cell therapy in the cornea: The emerging role of microenvironment

The cornea is an ideal testing field for cell therapies. Its highly ordered structure, where specific cell populations are sequestered in different layers, together with its accessibility, has allowed the development of the first stem cell-based therapy approved by the European Medicine Agency. Today, different techniques have been proposed for autologous and allogeneic limbal and non-limbal cell transplantation. Cell replacement has also been attempted in cases of endothelial cell decompensation as it occurs in Fuchs dystrophy: injection of cultivated allogeneic endothelial cells is now in advanced phases of clinical development. Recently, stromal substitutes have been developed with excellent integration capability and transparency. Finally, cell-derived products, such as exosomes obtained from different sources, have been investigated for the treatment of severe corneal diseases with encouraging results. Optimization of the success rate of cell therapies obviously requires high-quality cultured cells/products, but the role of the surrounding microenvironment is equally important to allow engraftment of transplanted cells, to preserve their functions and, ultimately, lead to restoration of tissue integrity and transparency of the cornea.

Comparative analysis of long-term results of three epithelial cell transplantation procedures for treating limbal stem cell deficiency

This study compared the long-term outcome of different epithelial transplantation techniques to treat limbal stem cell deficiency (LSCD). We conducted a retrospective 15-year comparative systematic cohort study of patients with LSCD who underwent either cultivated limbal epithelial transplantation (CLET), simple limbal epithelial transplantation (SLET), or cultivated oral mucosal epithelial transplantation (COMET). We reviewed the demographic data, etiology, LSCD severity, best-corrected visual acuity, surgical outcomes, and complications. A total of 103 eyes of 94 patients (mean age, 45.0 ± 16.4 years) with LSCD were enrolled. The most common cause of LSCD was chemical injury (42.7 %). The median follow-up time was 75 months. The success rates of CLET, SLET, and COMET were 45.5 %, 77.8 %, and 57.8 %, respectively. The 7-year survival rates after CLET, SLET, and COMET were 50.0 %, 72.2 %, and 53.2 %, respectively. Steven-Johnson syndrome (SJS) had a significantly lower survival rate than other causes (p < 0.001), but SLET had a significantly higher survival rate than CLET (p = 0.018) and COMET (p = 0.047). Visual improvement of more than four Snellen lines was achieved in 53.1 % of successful cases and 28.2 % of failed cases. SJS, Schirmer I test <5 mm, and the presence of postoperative recurrent epithelial defects were significant risk factors for a failed surgery. All epithelial transplantation techniques had favorable long-term surgical outcomes. More than half of the patients achieved a stable ocular surface and visual acuity improvement up to 7 years postoperatively. SLET tends to have a better surgical outcome than CLET and COMET, especially in patients with SJS.

Corneal blindness in the developing world: The role of prevention strategies

Corneal blindness is an important contributor to the burden of global blindness and has a greater prevalence in low-income countries of the developing world where resources and infrastructure are limited. The causes of corneal blindness too are different from high-income countries and include infectious keratitis, ocular trauma, and xerophthalmia. Persons with these indications tend to have unfavourable outcomes after corneal transplantation, limiting their chances of benefitting from this sight-saving procedure. However, most causes of corneal blindness in the developing world are preventable. This highlights the importance of understanding the unique challenges in these regions and the need for targeted interventions. This article discusses various prevention strategies, including primordial, primary, and secondary prevention, aimed at reducing the burden of corneal blindness in low-income countries. These include capacity building, training, and awareness campaigns to reduce the risk factors of ocular trauma, infectious keratitis, and to improve access to first aid. It is also important to promote safe eye practices and tackle nutritional deficiencies through public health interventions and policy changes. Providing the required training to general ophthalmologists in the management of basic corneal surgeries and diseases and enhancing the accessibility of eye care services in rural areas will ensure early treatment and prevent sequelae. Current treatment modalities belong to the tertiary level of prevention and are largely limited to corneal transplantation. In developing nations, there is a scarcity of donor corneal tissue necessitating an urgent expansion of eye banking services. Alternative approaches to corneal transplantation such as 3D printed corneas, cultured stem cells, and biomaterials should also be explored to meet this demand. Thus, there is a need for collaborative efforts between healthcare professionals, policymakers, and communities to implement effective prevention strategies and reduce the prevalence of corneal blindness in the developing world.

Neovascularization against autologous SLET donor grafts despite successful corneal epithelialization and graft adherence

PURPOSE

To report a case of neovascularization against autologous grafts after simple limbal epithelial transplantation (SLET) despite successful corneal epithelialization, as well as its subsequent regression without intervention.

METHODS

A case report and review of the literature.

RESULTS

A 52-year-old woman underwent uncomplicated autologous SLET for asymmetric limbal stem cell deficiency (LSCD) in the left eye. One month after the surgery, the patient had successful adherence of the graft and corneal epithelialization; however, new neovascularization developed in the left eye towards the graft sites. With only a slow taper of topical prednisolone acetate and polymyxin b/trimethoprim, the neovascularization regressed to ghost vessels over the following three months with improvement of her LSCD symptoms and increased clarity of her cornea.

CONCLUSION

The limbus does not enjoy relative immune privilege like other parts of the eye; therefore, autologous limbal stem cell transplantation (along with the minimal immune response generated) is valuable for restoration of the ocular surface. Here, we describe neovascularization against autologous donor grafts despite an otherwise uncomplicated surgery and expected epithelialization course. Inflammation-mediated angiogenesis likely initiated the neovascularization, suggesting that immune mediators of inflammation may be inadvertently part of the graft tissue in bilateral LSCD.

Advances in Cell Transplantation Therapy for Limbal Stem Cell Deficiency

BACKGROUND

Limbal stem cells (LSCs) are essential for maintaining corneal transparency and ocular surface integrity. Many external factors or genetic diseases can lead to corneal limbal stem cell deficiency (LSCD), resulting in the loss of barrier and corneal epithelial cell renewal functions. Stem cell transplantation is one of the primary treatments for LSCD, including limbal transplantation and cultivated limbal epithelial transplantation. In addition, a variety of non-limbal stem cell lines have been experimented with for LSCD treatment. Biological scaffolds are also used to support in vitro stem cell culture and transplantation. Here, we review the mechanisms of corneal maintenance by LSCs, the clinical stage and surgical treatment of LSCD, the source of stem cells, and the biological scaffolds required for in vitro culture.

METHODS

This study is a narrative retrospective study aimed at collecting available information on various aspects of surgical treatments for LSCD. Relevant literature was searched in a range of online databases, including Web of Science, Scopus, and PubMed from 2005 to March, 2023.

RESULTS

A total of 397 relevant articles were found, and 49 articles with strong relevance to the studies in this paper were obtained and analyzed. Moreover, 11 of these articles were on the concept of LSCD and the mechanism of LESCs maintaining the corneal epithelium, 3 articles on the staging and grading of LSCD, 17 articles on cell transplantation methods and donor cell sources, and 18 articles on scaffolds for delivering stem cells. We also summarized the advantages and disadvantages of different cell transplantation methods and the benefits and limitations of scaffolds based on the above literature.

CONCLUSION

The treatment of LSCD is determined by the clinical stage and whether it involves monocular or binocular eyes. Appropriate surgical techniques should be taken for LSCD patients in order to reconstruct the ocular surface, relieve symptoms, and restore visual function. Meanwhile, biological scaffolds assist in the ex vivo culture and implantation of stem cells.

Midterm Outcomes of Autologous Glueless Simple Limbal Epithelial Transplantation for Unilateral Limbal Stem Cell Deficiency

PURPOSE

The aim of this study was to report the midterm outcomes of glueless simple limbal epithelial transplantation (G-SLET) as a novel modification of limbal stem cell transplantation in patients with unilateral limbal stem cell deficiency (LSCD).

METHODS

This was a single-center, retrospective, interventional case series. Analysis of the 6 months interim outcomes was performed for 11 patients with unilateral LSCD who underwent G-SLET without simultaneous keratoplasty. The primary outcome measure was clinical success, which was defined as a completely epithelialized, avascular, and stable corneal surface. Secondary outcome measures included LSCD staging, improvement in visual acuity, and corneal grading of the recipient eye before and after the intervention. Adverse events were monitored throughout the study period.

RESULTS

At 6-month follow-up, clinical success was achieved in 9 of the 11 cases (81.8%) and partial success was observed in 2 cases (18.2%). Among the patients in the cohort, 54.5% improved to stage 0 LSCD. Seven patients experienced enhancement in visual acuity. All corneal grading parameters improved significantly. Six adverse events were registered in 5 cases and were successfully managed. An extended scar in the donor eye was observed in 1 patient.

CONCLUSIONS

This study demonstrated the high efficacy and safety of the G-SLET technique in the management of unilateral LSCD. G-SLET should be considered as a viable alternative to the"classic" SLET technique, specifically in the geographic areas where the availability of the fibrin glue is limited due to regulatory, economical, or any other reasons.

Safety and Efficacy of Contact Lenses in Eyes After Simple Limbal Epithelial Transplantation

PURPOSE

The aim of this study was to evaluate the safety and efficacy of contact lenses (CLs) in eyes after simple limbal epithelial transplantation (SLET) for limbal stem cell deficiency (LSCD).

METHODS

This retrospective study included 61 eyes with partial or total LSCD which underwent SLET and were fitted with corneal or scleral rigid gas-permeable CLs. The primary outcome measure was best-corrected visual acuity (BCVA) with CLs.

RESULTS

The median age at presentation was 22 years. The most common cause of LSCD was chemical injury [47/61 eyes (77%)]. Twenty-seven eyes (44%) were fitted with corneal rigid gas-permeable lenses, while 34 eyes (56%) were prescribed scleral lenses. The median duration of interval between SLET and CL trial was 10 months (interquartile range: 4-17). The median preoperative BCVA was logarithm of minimal angle of resolution (logMAR) 1.8. This improved to logMAR 1 ( P < 0.001) after SLET and to logMAR 0.6 ( P < 0.001) with CLs. Eyes with chemical injury (logMAR 1 vs. 0.6, P = 0.0001), grade 1 (logMAR 0.8 vs. 0.4, P < 0.0001), and grade 2 (logMAR 0.9 vs. 0.6, P = 0.004) corneal scarring had better improvement in BCVA with CLs. No complications were noted until the last follow-up visit.

CONCLUSIONS

CLs, both corneal and scleral lenses, provide significant visual improvement in eyes after SLET with residual corneal scarring. These can be safely prescribed in such eyes without any adverse effects. This option can be considered before offering keratoplasty in these eyes.

Ocular Surface Regeneration by Limbal Stem Cells Therapies: State of the Art, Challenges, and Perspectives

Limbal stem cells (LSCs) are adult stem cells located at the limbus ensuring the continuous renewal of the corneal epithelium, critical to maintain an optimal visual function. Damages to the LSCs or their niche microenvironment lead to limbal stem cell deficiency (LSCD), a potentially blinding disease. Transplantation of LSCs as a treatment for severe to total LSCD has gained popularity since 1980s, owing to the clinical success of the first direct limbal autograft transplantation. Recent advances in the understanding of the LSCs' molecular identity and regulation have enabled preclinical and clinical advancements of promising LSCs therapies. However, lack of standardization of the diagnostic methods, staging of the disease severity, manufacturing process, and clinical outcome measures have hindered the advancement of the therapy. To move these therapies to the clinic, optimization and standardization of the diagnostic strategy, cell product manufacturing, and assessment of clinical efficacy with potency assays are key points to the development of customized therapies. Recent findings suggest that residual LSCs exist in eyes presenting with clinical signs of total LSCD, which opens new therapeutic strategies for eyes with partial LSCD. Prospective, randomized, multicentric controlled clinical trials are necessary to determine the efficacy of different LSCs therapies for different stages of LSCD using a set of standardized outcome measures.

Sequelae of carbide-related thermo-chemical injury: A retrospective analysis

Purpose

To describe the outcomes of eyes with calcium carbide (CaC2)-related thermo-chemical injury.

Methods

This study included 28 eyes of 23 patients who presented with calcium carbide-related ocular burns. Only patients with more than three months of follow-up were included. Group A included 16 eyes with Dua's Grade I-III burns, while Group B included 12 eyes with Grade IV-VI burns. Electronic medical records were reviewed to provide data on the etiology of burn, presenting clinical signs and visual acuity, sequelae, and surgical interventions performed, both in the acute and chronic phases.

Results

The overall mean age was 28.48 ± 11.8 years. Fifteen patients were injured while using carbide to create an explosion to scare away animals on farms. The median presenting BCVA (best-corrected visual acuity) in Group A (20/160) was significantly better than in Group B [(20/2000) (P = 0.002)]. Five eyes in Group A and one eye in Group B underwent medical management. There was no difference in the duration of follow-up for both groups (P = 0.24). The median final BCVA in Group A (20/32) was significantly better than in Group B [(20/200) (P = 0.02)]. Two eyes in Group A and nine eyes in Group B developed LSCD. Two eyes in Group B were phthisical at the last visit.

Conclusion

Calcium carbide-related ocular injuries can result in significant visual morbidity in young adults. Early presentation and management may improve outcomes. Prevention of these injuries by increasing awareness and increasing advocacy efforts is necessary.

Why Are Corneal Specialists Resistant to Treating Patients Who Have Severe Ocular Surface Disease With Limbal Stem Cell Deficiency?

PURPOSE

To highlight the paucity of surgeons performing ocular surface stem cell transplantation with systemic immunosuppression (OSSTx with SI) for limbal stem cell deficiency (LSCD) patients, suboptimal treatments for LSCD, and obstacles to adoption.

METHODS

A review of the Eye Bank Association of America annual reports and the authors' case volume for OSSTx with SI was performed. Examination of the published literature on corneal surgeries, especially for LSCD, was completed. These findings were combined with our clinical observations to develop this editorial.

RESULTS

Despite techniques and protocols for OSSTx with SI published more than 30 years ago for the treatment of severe bilateral LSCD, only a small number of corneal specialists have adopted these techniques. There is a paucity of attention to this population of patients, with minimal publications to advance this area of our field. We are too often referred patients with LSCD and severe ocular surface disease that have had suboptimal treatments such as penetrating keratoplasties or primary keratoprostheses. Hesitancy for adopting OSSTx with SI is likely due to a lack of exposure to these procedures during training and fear of systemic immunosuppression. Corneal surgeons are likely unaware of the safety of systemic immunosuppression with appropriate monitoring especially when comanaging these patients with an organ transplant specialist.

CONCLUSION

There is a large unmet need for the treatment of corneal blindness secondary to conjunctival and LSCD. For the vast majority of patients, OSSTx should be the first surgical choice to treat these eyes. We hope major ophthalmology centers will meet this need by building programs, and groups of corneal surgeons should collaborate to create regional centers to make this treatment more accessible to help this population.

Cultivated autologous limbal epithelial cell (CALEC) transplantation: Development of manufacturing process and clinical evaluation of feasibility and safety

To treat unilateral limbal stem cell (LSC) deficiency, we developed cultivated autologous limbal epithelial cells (CALEC) using an innovative xenobiotic-free, serum-free, antibiotic-free, two-step manufacturing process for LSC isolation and expansion onto human amniotic membrane with rigorous quality control in a good manufacturing practices facility. Limbal biopsies were used to generate CALEC constructs, and final grafts were evaluated by noninvasive scanning microscopy and tested for viability and sterility. Cultivated cells maintained epithelial cell phenotype with colony-forming and proliferative capacities. Analysis of LSC biomarkers showed preservation of "stemness." After preclinical development, a phase 1 clinical trial enrolled five patients with unilateral LSC deficiency. Four of these patients received CALEC transplants, establishing preliminary feasibility. Clinical case histories are reported, with no primary safety events. On the basis of these results, a second recruitment phase of the trial was opened to provide longer term safety and efficacy data on more patients.

Case Report: Simultaneous penetrating keratoplasty with autologous simple limbal epithelial transplantation as an alternative to keratoprosthesis

Introduction and importance: This case report highlights the multidisciplinary approach required to achieve successful anatomical and functional outcomes, in an eye with total limbal stem cell deficiency (LSCD) associated with underlying corneal scarring and thinning. Presentation of case: A 59-year-old gentleman had poor visual recovery in the right eye (RE) following accidental carbide blast, 1-year before presenting to us. The visual acuity was counting fingers and clinical examination revealed cicatricial entropion involving the upper eyelid, total LSCD, corneal scarring with a central descemetocele and cataract in the RE. Prior to ocular surface reconstruction, entropion correction was performed. Three months later, penetrating keratoplasty combined with cataract surgery and intraocular lens implantation (penetrating keratoplasty (PK) triple), with autologous simple limbal epithelial transplantation (SLET) was performed. The visual acuity was 20/100, 18 months after the surgery, with a clear well-epithelized corneal graft and stable ocular surface. Discussion: LSCD is caused by a decrease in the population and /or function of the limbal epithelial stem cells. Limbal stem cell transplantation (LSCT) is warranted in eyes with total LSCD. In eyes with coexisting corneal scarring, LSCT alone may be inadequate to restore the vision. These eyes require simultaneous or sequential lamellar or full-thickness corneal transplantation for visual rehabilitation. Though, the existing literature favors a sequential approach, where LSCT is performed first followed by corneal transplantation, under certain circumstances such as a thin underlying cornea like in our case, corneal transplantation may have to be combined with LSCT to achieve optimal outcomes. Conclusion: Combining autologous SLET with PK can be performed for visual rehabilitation in eyes with unilateral total LSCD and underlying corneal thinning. Corneal and limbal graft survival is prolonged if existing adnexal comorbidities are addressed before any surgical intervention is planned and adequate time interval is allowed for the surface inflammation to subside.

Case Report: Simultaneous penetrating keratoplasty with autologous simple limbal epithelial transplantation as an alternative to keratoprosthesis

Introduction and importance: This case report highlights the multidisciplinary approach required to achieve successful anatomical and functional outcomes, in an eye with total limbal stem cell deficiency (LSCD) associated with underlying corneal scarring and thinning. Presentation of case: A 59-year-old gentleman had poor visual recovery in the right eye (RE) following accidental carbide blast, 1-year before presenting to us. The visual acuity was counting fingers and clinical examination revealed cicatricial entropion involving the upper eyelid, total LSCD, corneal scarring with a central descemetocele and cataract in the RE. Prior to ocular surface reconstruction, entropion correction was performed. Three months later, penetrating keratoplasty combined with cataract surgery and intraocular lens implantation (penetrating keratoplasty (PK) triple), with autologous simple limbal epithelial transplantation (SLET) was performed. The visual acuity was 20/100, 18 months after the surgery, with a clear well-epithelized corneal graft and stable ocular surface. Discussion: LSCD is caused by a decrease in the population and /or function of the limbal epithelial stem cells. Limbal stem cell transplantation (LSCT) is warranted in eyes with total LSCD. In eyes with coexisting corneal scarring, LSCT alone may be inadequate to restore the vision. These eyes require simultaneous or sequential lamellar or full-thickness corneal transplantation for visual rehabilitation. Though, the existing literature favors a sequential approach, where LSCT is performed first followed by corneal transplantation, under certain circumstances such as a thin underlying cornea like in our case, corneal transplantation may have to be combined with LSCT to achieve optimal outcomes. Conclusion: Combining autologous SLET with PK can be performed for visual rehabilitation in eyes with unilateral total LSCD and underlying corneal thinning. Corneal and limbal graft survival is prolonged if existing adnexal comorbidities are addressed before any surgical intervention is planned and adequate time interval is allowed for the surface inflammation to subside.

Clinical applications of bioengineered tissue-cellular products for management of corneal diseases

PURPOSE OF REVIEW

To discuss bioengineered tissue-cellular products for treatment of corneal diseases that are currently in clinical use. These include tissue-cellular products that have received regulatory approval, are being used off-label in clinical practice, or are in active use in clinical trials.

RECENT FINDINGS

Due to the global shortage of donor corneal tissue, significant efforts have been made to develop bioengineering tissue-cellular products that can replace or augment the use of cadaveric tissue for corneal transplantation. The development of carrier substrates to support transplantation of cultivated limbal epithelial transplantation (CLET) has been a growing area of research. CLET offers a promising therapeutic alternative to conventional simple limbal epithelial transplantation and keratolimbal allografts for treatment of limbal stem cell deficiency. Engineered tissue matrices and porcine-derived corneas are potential alternatives to human donor tissue in anterior lamellar keratoplasty for corneal ulcers and scars, as well as intrastromal transplants for advanced keratoconus. For endothelial disease, substrate supported cultured endothelial cell grafts, and synthetic barrier devices are promising alternative to traditional endothelial keratoplasties.

SUMMARY

There has been increasing interest in cellular and acellular bioengineered tissue-cellular and synthetic products for treatment of corneal diseases, and many of these products have already seen clinical use. Industry and academia have important roles in advancing these products to later phase clinical trials and comparing them to conventional allograft approaches. Future development of full thickness donor corneas with cultivated epithelium, endothelium, and stromal keratocytes in a biosynthetic matrix will likely be an important next step in tissue alternatives. Continued progress in this field will be critical for addressing the global disease burden from corneal blindness.

Corneal epithelial development and homeostasis

The corneal epithelium (CE), the most anterior cellular structure of the eye, is a self-renewing stratified squamous tissue that protects the rest of the eye from external elements. Each cell in this exquisite three-dimensional structure needs to have proper polarity and positional awareness for the CE to serve as a transparent, refractive, and protective tissue. Recent studies have begun to elucidate the molecular and cellular events involved in the embryonic development, post-natal maturation, and homeostasis of the CE, and how they are regulated by a well-coordinated network of transcription factors. This review summarizes the status of related knowledge and aims to provide insight into the pathophysiology of disorders caused by disruption of CE development, and/or homeostasis.

Insights into the clinical development of regenerative medical products through a comparison of three cell-based products recently approved for limbal stem cell deficiency

Three regenerative medical products for limbal stem cell deficiency (LSCD), a rare and intractable ocular surface disease, have recently been approved in Japan. To our knowledge, this is the first time multiple stem-cell-based medical products have been approved for the same ocular disease. Development plans and study designs for each product differ, resulting in differences in indications. Since cell-based products have a heterogeneous formulation and often target rare diseases, they require a flexible approach to development. This review article describes the status and prospects of the clinical development of regenerative medical products by summarizing the issues of the three products from the Pharmaceuticals and Medical Devices Agency (PMDA) standpoint. Implementing stem cell-based products is challenging, requiring scientific and flexible review by regulatory authorities. To overcome these issues in the development process, developers and regulatory authorities need to communicate and fully discuss study protocols from the early stage of development.

Technique for the Management of Extensive Ocular Surface Lipodermoid Involving the Cornea of Children

PURPOSE

Ocular surface lipodermoids with corneal involvement may require surgical intervention; if deep, ocular surface reconstruction with lamellar corneal tissue or amniotic membrane may be needed. We describe a staged technique using autologous ipsilateral simple limbal epithelial transplantation.

METHODS

After verifying sparing of Descemet membrane, the conjunctival portion of the lipodermoid was debulked in the first stage. Six weeks later, the corneal portion was excised, followed by autologous ipsilateral simple limbal epithelial transplantation to promote rapid reepithelialization of the residual stromal bed. Temporary tarsorrhaphy was used for patient comfort and to expedite ocular surface healing.

RESULTS

Three eyes of 3 children with grade III large ocular surface lipodermoids that encroached the visual axis and hindered proper eyelid closure underwent surgery without complications. In all cases, the visual axis was cleared and eyelid closure was improved. At the last follow-up (mean 35.7 months, median 36.0 months), the bed of the original dermoid showed minimal haze in 1 case, while 2 eyes developed small pseudopterygium; best spectacle-corrected visual acuity improved from 20/200 to 20/70 in the first case, from fix and follow to 20/50 in the second case, and remained fix and follow in the last case, but this child had congenital hydrocephalus with severe developmental delay.

CONCLUSIONS

This surgical technique is a promising option for children with grade III large ocular surface lipodermoids given its effectiveness in clearing the visual axis and in improving eyelid closure. Moreover, it does not require lamellar corneal transplantation or intervention to the fellow eye.

Clinical efficacy of a new surgical technique of oral mucosal epithelial transplantation for severe ocular surface disorders

BACKGROUND

Severe ocular surface disorders are one of the major blinding diseases, and a paucity of original tissue obscures successful reconstruction. We developed a new surgical technique of direct oral mucosal epithelial transplantation (OMET) to reconstruct severely damaged ocular surfaces in 2011. This study elaborates on the clinical efficacy of OMET.

METHODS

A retrospective review of patients with severe ocular surface disorders who underwent OMET from 2011 to 2021 at the Department of Ophthalmology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine was conducted. Patients who were followed up for at least 3 months postoperatively and had sufficient pre or postoperative records were included. Surgical efficacy was evaluated by comparing the best-corrected visual acuity (BCVA), corneal transparency, neovascularization grade, and symblepharon grade. Additionally, postoperative ocular surface impression cytology was used to study the morphology of the newborn epithelial cells.

RESULTS

Forty-eight patients (49 eyes; mean age: 42.55 ± 12.40 years, range:12-66 years) were enrolled in the study. The etiology included chemical burns (30 eyes), thermal burns (16 eyes), explosive injuries (1 eye), Stevens-Johnson syndrome (1 eye), and multiple pterygiums (1 eye). The mean follow-up period was 25.97 ± 22.99 months. Postoperatively, 29 eyes (59.18%) showed improved corneal transparency, 26 eyes (53.06%) had improved BCVA, 47 eyes (95.92%) had a stable epithelium until the final follow-up, 44 eyes (89.80%) had a reduced neovascularization grade. Of the 20 eyes with preoperative symblepharon, 15 (75%) were completely resolved, and five (25%) were partially resolved. Impression cytological studies showed no postoperative conjunctival invasion onto the corneal surface.

CONCLUSIONS

OMET is a safe and effective surgical technique for reconstruction in severe ocular surface disorder by maintaining a stable epithelium and reducing the neovascularization and symblepharon grade.

Single mRNA detection of Wnt signaling pathway in the human limbus

Limbal epithelial stem/progenitor cells (LSCs) are adult stem cells located at the limbus, tightly regulated by their close microenvironment. It has been shown that Wnt signaling pathway is crucial for LSCs regulation. Previous differential gene profiling studies confirmed the preferential expression of specific Wnt ligands (WNT2, WNT6, WNT11, WNT16) and Wnt inhibitors (DKK1, SFRP5, WIF1, FRZB) in the limbal region compared to the cornea. Among all frizzled receptors, frizzled7 (Fzd7) was found to be preferentially expressed in the basal limbal epithelium. However, the exact localization of Wnt signaling molecules-producing cells in the limbus remains unknown. The current study aims to evaluate the in situ spatial expression of these 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7. Wnt ligands, DKK1, and Fzd7 expression were scattered within the limbal epithelium, at a higher abundance in the basal layer than the superficial layer. SFRP5 expression was diffuse among the limbal epithelium, whereas WIF1 and FRZB expression was clustered at the basal limbal epithelial layer corresponding to the areas of high levels of Fzd7 expression. Quantitation of the fluorescence intensity showed that all 4 Wnt ligands, 3 Wnt inhibitors (WIF1, DKK1, FRZB), and Fzd7 were highly expressed at the basal layer of the limbus, then in a decreasing gradient toward the superficial layer (P < 0.05). The expression levels of all 4 Wnt ligands, FRZB, and Fzd7 in the basal epithelial layer were higher in the limbus than the central cornea (P < 0.05). All 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7 were also highly expressed in the limbal stroma immediately below the epithelium but not in the corneal stroma (P < 0.05). In addition, Fzd7 had a preferential expression in the superior limbus compared to other limbal quadrants (P < 0.05). Taken together, the unique expression patterns of the Wnt molecules in the limbus suggests the involvement of both paracrine and autocrine effects in LSCs regulation, and a fine balance between Wnt activators and inhibitors to govern LSC fate.

Management of limbal stem cell deficiency by amnion-assisted conjunctival epithelial redirection using vacuum-dried amniotic membrane and fibrin glue

PURPOSE

To study the outcome of a modified amnion-assisted conjunctival epithelial redirection (ACER) technique using vacuum-dried amnion (Omnigen) and fibrin glue for managing total limbal stem cell deficiency (LSCD).

METHOD

A retrospective, interventional case series of all patients with total LSCD who underwent limbal stem cell transplant (LSCT) using the modified ACER procedure between 2016 and 2019. The outcome was defined as: (1) success: complete corneal re-epithelialisation without conjunctivalisation; (2) partial success: sub-total corneal re-epithelialisation with partial non-progressive conjunctivalisation sparing the visual axis and (3) failure: conjunctivalisation affecting the visual axis.

RESULTS

Ten patients (six men), with a mean age of 46.2±18.4 years, were included. The mean follow-up was 23.0±13.9 months. Causes of LSCD were chemical eye injury (30%), congenital aniridia-related keratopathy (30%), ocular surface malignancy (20%), Steven-Johnson syndrome (10%) and contact lens overuse (10%). 50% were bilateral. The time from diagnosis to ACER (for acquired causes) was 45.6±44.4 months. 80% of patients achieved a complete/partial success following ACER and 20% of patients required repeat LSCT. Auto-LSCT was associated with a significantly higher chance of success than allo-LSCT (p=0.048). The mean best-corrected-visual-acuity (logMAR) improved significantly from 1.76±0.64 preoperatively to 0.94±0.94 at final follow-up (p=0.009). Omnigen was available off-the-shelf stored at room temperature and its transparency enabled visualisation of the healing epithelium beneath.

CONCLUSION

LSCT using the modified ACER serves as an effective ocular surface reconstruction technique in managing total LSCD and improving vision. Vacuum-dried amnion provides advantages of easy handling, transparency and storage at room temperature.

Allogeneic Limbal Transplants Integrate into the Corneal Surface and Lead to an Improved Visual Acuity

Limbal stem cell deficiency (LSCD) severely impairs vision and can lead to blindness. LSCD causes include chemical burns, infections, multiple previous operations and congenital malformations. Allogeneic limbal transplantation is a procedure for treating LSCD where prepared limbal tissue is attached using a double running suture during allogeneic penetrating keratoplasty (PKP). A total of 22 patients underwent ALT surgery between February 2019 and June 2022 at the University Hospital Halle (Saale). Regular follow-up was performed postoperatively every three months and included visual acuity testing, pressure measurement, slit lamp microscopic examination, fundoscopy, corneal topography and anterior segment optical coherence tomography (AS-OCT). The mean patient age was 69.5 years, and the mean follow-up was 19 months. All included patients had LSCD and multiple previous surgeries. Patient LSCD etiology was 59% infectious and 41% traumatic. ALTs integrated into corneal surfaces in all patients, demonstrated on AS-OCT. Since most patients initially received allogeneic limbal transplants, none of the operated eyes had surgical complications. Overall, visual acuity improved postoperatively from an initial 2.06 to 1.44 logarithm of the minimum angle of resolution (logMAR). Allogeneic limbal transplantation can be used to treat LSCD and its integration into the surrounding corneal tissue can be observed on AS-OCT.

Concise Review: Bioengineering of Limbal Stem Cell Niche

The corneal epithelium is composed of nonkeratinized stratified squamous cells and has a significant turnover rate. Limbal integrity is vital to maintain the clarity and avascularity of the cornea as well as regeneration of the corneal epithelium. Limbal epithelial stem cells (LESCs) are located in the basal epithelial layer of the limbus and preserve this homeostasis. Proper functioning of LESCs is dependent on a specific microenvironment, known as the limbal stem cell niche (LSCN). This structure is made up of various cells, an extracellular matrix (ECM), and signaling molecules. Different etiologies may damage the LSCN, leading to limbal stem cell deficiency (LSCD), which is characterized by conjunctivalization of the cornea. In this review, we first summarize the basics of the LSCN and then focus on current and emerging bioengineering strategies for LSCN restoration to combat LSCD.

Diagnostic Algorithm for Surgical Management of Limbal Stem Cell Deficiency

BACKGROUND

Limbal stem cell deficiency (LCSD) presents several challenges. Currently, there is no clearly defined systematic approach to LSCD diagnosis that may guide surgical tactics.

METHODS

The medical records of 34 patients with LSCD were analyzed. Diagnostic modalities included standard (visometry, tonometry, visual field testing, slit-lamp biomicroscopy with corneal fluorescein staining, Schirmer test 1, ultrasonography) and advanced ophthalmic examination methods such as anterior segment optical coherence tomography, in vivo confocal microscopy, impression cytology, and enzyme-linked immunoassay.

RESULTS

Standard ophthalmological examination was sufficient to establish the diagnosis of LSCD in 20 (58.8%) cases, whereas advanced evaluation was needed in 14 (41.2%) cases. Depending on the results, patients with unilateral LSCD were scheduled to undergo glueless simple limbal epithelial transplantation (G-SLET) or simultaneous G-SLET and lamellar keratoplasty. Patients with bilateral LSCD with normal or increased corneal thickness were enrolled in the paralimbal oral mucosa epithelium transplantation (pLOMET) clinical trial.

CONCLUSIONS

Based on the diagnostic and surgical data analyzed, the key points in LSCD diagnosis were identified, helping to guide the surgeon in selecting the appropriate surgical procedure. Finally, we proposed a novel step-by-step diagnostic algorithm and original surgical guidelines for the treatment of patients with LSCD.

Deep anterior lamellar limbo-keratoplasty for bilateral limbal stem cell deficiency with corneal scarring in chemical injury sequelae: Two case reports

INTRODUCTION AND IMPORTANCE

This report describes a new technique of deep anterior lamellar limbo-keratoplasty for the management of bilateral limbal stem cell deficiency (LSCD) with corneal scarring.

PRESENTATION OF CASES

A 45-year-old male presented with chronic sequelae of ocular chemical injury and had bilateral total LSCD with corneal scarring. The visual acuity (VA) in the right eye was counting fingers. A large diameter deep anterior lamellar limbo-keratoplasty (DAL-LK) was carried out and the donor cornea and limbus were sourced from a single tissue. The VA at the last visit, 2.5 years after the surgery was 20/80. A similar presentation was seen in a 31-year-old male with a VA of 20/320 in the right eye. He underwent a DAL-LK and 3 years after the procedure, the VA was 20/60. Both grafts remained clear with no episodes of rejection until the last follow up visit.

DISCUSSION

Limbal stem cell transplantation with keratoplasty or a keratoprosthesis is required to manage bilateral LSCD with stromal scarring. The former necessitates multiple interventions while the latter is associated with several globe threatening complications. DAL-LK was devised to overcome these disadvantages and offers a simple, single staged technique of simultaneously transplanting the corneal stroma with the limbal stem cells. As the host endothelium is preserved, there is no risk of rejection episodes.

CONCLUSION

DAL-LK can successfully restore stability of the ocular surface and visually rehabilitate cases with bilateral LSCD and stromal scarring. The procedure has stable long-term outcomes with a good safety profile.

Current Advancements in Corneal Cell-Based Therapy

Corneal epithelial stem cells (CEpSCs) mostly reside at the limbal area and are responsible for tissue homeostasis throughout life. Once complete CEpSC deficiency occurs, regenerative medicine cell-based therapy using CEpSCs or their alternatives can provide successful clinical outcomes. Due to an improved understanding of CEpSCs and mucosal epithelial stem cells, major advancements have been made over the past few decades in in vivo and ex vivo cell-based ocular surface reconstruction therapies for the treatment of severe ocular surface diseases. New therapeutic concepts and clinical strategies are emerging for the treatment of corneal endothelial dysfunction. For example, unlike corneal epithelial cells, in vivo corneal endothelial cells (CECs) stop proliferating and are arrested in the G1 phase of the cell cycle due to cell-to-cell contact inhibition and exposure to a high concentration of transforming growth factor-beta in the aqueous humor. Thus, the production of CECs with good functionality in culture has consistently been difficult. To solve this problem, Rho-associated protein kinase inhibition has taken center stage, as it not only makes the production of human CECs in culture closely mimic the functional characteristics of in vivo healthy CECs possible but also helps sustain those biological properties. Thus, cultured human CEC injection therapy is now moving to the forefront for the treatment of corneal endothelial failure. Herein, we summarize key historical discoveries in corneal cell-based regenerative medicine and illustrate the concept of corneal cell therapy for the treatment of refractory corneal epithelial and endothelial diseases.

OUP accepted manuscript

The corneal epithelium serves to protect the underlying cornea from the external environment and is essential for corneal transparency and optimal visual function. Regeneration of this epithelium is dependent on a population of stem cells residing in the basal layer of the limbus, the junction between the cornea and the sclera. The limbus provides the limbal epithelial stem cells (LESCs) with an optimal microenvironment, the limbal niche, which strictly regulates their proliferation and differentiation. Disturbances to the LESCs and/or their niche can lead to the pathologic condition known as limbal stem cell deficiency (LSCD) whereby the corneal epithelium is not generated effectively. This has deleterious effects on the corneal and visual function, due to impaired healing and secondary corneal opacification. In this concise review, we summarize the characteristics of LESCs and their niche, and present the current and future perspectives in the management of LSCD with an emphasis on restoring the function of the limbal niche.

Effects of corneal epithelial superficial keratectomy in patients with focal limbal stem cell disease

Purpose

Irregular corneal epithelium in limbal stem cell disease can cause visual acuity to deteriorate substantially when it reaches the pupil. In this case series, we assessed the effectiveness of simple corneal epithelial superficial keratectomy in improving visual acuity in patients with irregular corneal epithelium in focal limbal stem cell disease covering the visual axis.

Observations

We performed simple corneal epithelial superficial keratectomy in four patients (five eyes) with irregular corneal epithelium covering the visual axis. The main outcome measures were best-corrected visual acuity, slit lamp findings with fluorescein staining, anterior segment optical coherence tomography and histopathology. In all five eyes, slit lamp findings showed uneven fluorescein staining in a spiral pattern, with impaired corneal epithelial smoothness and visual disturbance. We removed the irregular epithelium in all five eyes. Visual acuity in all the eyes was improved immediately after surgery, and good visual acuity and stable epithelium were maintained for the duration of the observation periods. Hematoxylin and eosin staining showed, normal squamous and columnar epithelial cells. Goblet cells were not detected.

Conclusionsand Importance

Corneal epithelial superficial keratectomy can lead to a pathological diagnosis by examining the removed epithelial tissues, and result in excellent therapeutic outcomes in focal limbal stem cell disease reaching the pupil.

Surgical Management of Unilateral Partial Limbal Stem Cell Deficiency: Conjunctival Autografts versus Simple Limbal Epithelial Transplantation

Purpose

To evaluate the clinical outcomes of conjunctival autograft (CAG) versus simple limbal epithelial transplant (SLET) for management of unilateral partial limbal stem cell deficiency (LSCD).

Methods

This retrospective, comparative, interventional case series evaluated 30 eyes of 30 patients with unilateral partial LSCD. After corneal pannus dissection, 17 patients underwent CAG where graft was harvested from the ipsilateral or contralateral eye, while 13 patients underwent SLET where limbal biopsy was harvested from the contralateral eye. The primary outcome measure was anatomical success in the form of restoration of a completely epithelised, stable, and avascular corneal surface at last follow-up.

Results

Both groups were comparable in terms of age at time of surgery, preoperative best-corrected visual acuity, median duration since injury, number of clock hours of limbus involved, and number of previous surgeries performed. The most common etiology for LSCD was chemical burns in both groups. The median duration of post-operative follow-up was 5.6 months [interquartile range [(IQR): 3.6–15.1] in the CAG group versus 6.2 months (IQR: 4.5–12.2) in the SLET group (p=0.75)]. The anatomical success rates were 86.5 ± 8.9% in the CAG group and 28.3 ± 13.7% in the SLET group at final follow-up visit (p = 0.025). Most failures in both groups occurred within the first 8 months after surgery.

Conclusion

For eyes with unilateral partial LSCD secondary to chemical burns, CAG is a safe and effective method for restoring the corneal epithelium. Limbal transplantation may not be necessary for the treatment of partial LSCD.

Outcomes of surgical interventions for the treatment of limbal stem cell deficiency

Background & objectives:

In the current scenario, with availability of different surgical procedures for limbal stem cell deficiency (LSCD), there exists no common consensus as to the standardization of the management protocol for the same. In addition, there also exists diversity in the views about the clinical diagnosis, ancillary investigations and clinical parameters. The objective of the present study was to evaluate the reported outcomes of surgical interventions for the management of LSCD.

Methods:

A systematic review of published literature on limbal stem cell transplantation (LSCT) was performed using Ovid Medline, Embase and PubMed for a duration of 2009 to 2019. Original studies including prospective, retrospective case series and randomized controlled trials, articles in English language, articles with access to full text and studies with more than or at least 10 patients were included in this review. Data related to clinical and visual outcomes were evaluated, and pool estimates of different surgeries were calculated using random-effects model and individually using Pearson’s Chi-square test.

Results:

A total of 1133 abstracts were evaluated. Finally, 17 studies were included for the analysis. Among these 17 studies, direct limbal lenticule transplantation was performed in five studies, of which autologous tissue from the fellow eye [conjunctival limbal autograft (CLAU)], allograft from a cadaver/live donor [keratolimbal allograft (KLAL)/conjunctival limbal allograft (CLAL)] and combination of CLAU plus KLAL were done in one, three and one studies, respectively. The ex vivo expanded cultivated limbal epithelial transplantation (CLET) was reported in six studies and simple limbal epithelial transplantation (SLET) in four studies. Two were comparative studies comparing CLET and CLAL (living-related CLAL) with cadaveric KLAL, respectively. Outcome analysis of the included studies showed significant heterogeneity. Calculated pool rate for various types of surgeries was calculated. The pool estimate for CLAL was 67.56 per cent [95% confidence interval (CI), 41.75-93.36; I²=83.5%, P=0.002]. For KLAL, this value was 63.65 per cent (95% CI, 31.38-95.91; I²=92.4%, P=0.000). Pool estimate for CLET was 78.90 per cent (95% CI, 70.51-87.28; I²=73.6%, P=0.001). Corresponding values for SLET were 79.08 per cent (95% CI, 74.10-84.07; I²=0.0%, P=0.619). CLAU and combination of CLAU plus KLAL were done in one study each; hence, statistical analysis could not be done. The functional outcome in terms of gain in visual acuity post-operatively was better in KLAL (P<0.005) and SLET group as compared to CLET group.

Interpretation & conclusions:

The present analysis suggests that though the anatomical success rates were almost identical between SLET, CLET, CLAL, and KLAL procedures, the functional success rates were better following KLAL and SLET procedures as compared to CLET. Decision for LSCT for cases of ocular burns based on either clinical judgement of the surgeon or individual diagnosis remains a suitable option.

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.

Wnt6 plays a complex role in maintaining human limbal stem/progenitor cells

The corneal epithelium is consistently regenerated by limbal stem/progenitor cells (LSCs), a very small population of adult stem cells residing in the limbus. Several Wnt ligands, including Wnt6, are preferentially expressed in the limbus. To investigate the role of Wnt6 in regulating proliferation and maintenance of human LSCs in an in vitro LSC expansion setting, we generated NIH-3T3 feeder cells to overexpress different levels of Wnt6. Characterization of LSCs cultured on Wnt6 expressing 3T3 cells showed that high level of Wnt6 increased proliferation of LSCs. Medium and high levels of Wnt6 also increased the percentage of small cells (diameter ≤ 12 µm), a feature of the stem cell population. Additionally, the percentage of cells expressing the differentiation marker K12 was significantly reduced in the presence of medium and high Wnt6 levels. Although Wnt6 is mostly known as a canonical Wnt ligand, our data showed that canonical and non-canonical Wnt signaling pathways were activated in the Wnt6-supplemented LSC cultures, a finding suggesting that interrelationships between both pathways are required for LSC regulation.

Longitudinal Changes in Corneal Epithelial Thickness and Reflectivity following Simple Limbal Epithelial Transplantation: An Optical Coherence Tomography-Based Study

PURPOSE

To describe the changes in corneal epithelial thickness and reflectivity following simple limbal epithelial transplantation (SLET) using anterior segment optical coherence tomography (ASOCT).

METHODS

This was a prospective imaging study of 31 eyes of 29 patients who had undergone autologous or allogeneic SLET for limbal stem cell deficiency and had stable, avascular surfaces postoperatively. ASOCT scans of all four quadrants were taken preoperatively and at 1-week, 1-month, 3-month, 6-month, and 1-year postoperative time points in the eyes undergoing SLET. Baseline scans were also taken from the normal eye in unilateral cases. The following parameters were obtained from the scans: (i) epithelial thickness (ET), (ii) stromal thickness, (iii) total corneal thickness, (iv) epithelial reflectivity (ER), (v) stromal reflectivity, and (vi) epithelial/stromal (ES) reflectivity ratio.

RESULTS

Chemical injury (24 eyes, 77.4%) was the most common indication for surgery. There was a significant improvement in the ET (184.8 ± 117.1 vs 60.3 ± 10 µm, p < .0001) and ER (144.5 ± 26.4 vs 120.9 ± 28.9, p < .0001) within the initial postoperative period following SLET, which remained stable at the end of 1 year follow-up. There was no difference in the ET of the post-SLET and normal eyes after the 3-month timepoint and this normalization was maintained until the end of the first year. A significant normalization was also noted in the ES reflectivity ratio at the end of 1 year (2.1 ± 0.8 vs 1 ± 0.2, p < .001). A significant correlation was found between the final visual acuity and the total corneal thickness (r = 0.942, p = .005).

CONCLUSION

There is a significant improvement in the epithelial thickness and reflectivity of the cornea in eyes undergoing SLET. ASOCT provides a reliable objective measure of these changes and can be used to monitor the outcomes in these eyes postoperatively.

Wound healing of the corneal epithelium: a review

The corneal epithelium (CE) forms the outermost layer of the cornea. Despite its thickness of only 50 μm, the CE plays a key role as an initial barrier against any insults to the eye and contributes to the light refraction onto the retina required for clear vision. In the event of an injury, the cornea is equipped with many strategies contributing to competent wound healing, including angiogenic and immune privileges, and mechanotransduction. Various factors, including growth factors, keratin, cytokines, integrins, crystallins, basement membrane, and gap junction proteins are involved in CE wound healing and serve as markers in the healing process. Studies of CE wound healing are advancing rapidly in tandem with the rise of corneal bioengineering, which employs limbal epithelial stem cells as the primary source of cells utilizing various types of biomaterials as substrates.

The Limbal Niche and Regenerative Strategies

The protective function and transparency provided by the corneal epithelium are dependent on and maintained by the regenerative capacity of limbal epithelial stem cells (LESCs). These LESCs are supported by the limbal niche, a specialized microenvironment consisting of cellular and non-cellular components. Disruption of the limbal niche, primarily from injuries or inflammatory processes, can negatively impact the regenerative ability of LESCs. Limbal stem cell deficiency (LSCD) directly hampers the regenerative ability of the corneal epithelium and allows the conjunctival epithelium to invade the cornea, which results in severe visual impairment. Treatment involves restoring the LESC population and functionality; however, few clinically practiced therapies currently exist. This review outlines the current understanding of the limbal niche, its pathology and the emerging approaches targeted at restoring the limbal niche. Most emerging approaches are in developmental phases but show promise for treating LSCD and accelerating corneal regeneration. Specifically, we examine cell-based therapies, bio-active extracellular matrices and soluble factor therapies in considerable depth.

Referral Patterns of Patients with Limbal Stem Cell Deficiency to a Specialized Tertiary Center in the United Kingdom

INTRODUCTION

Limbal stem cell deficiency (LSCD) is a potentially blinding disease; hence, referral to a specialist service is becoming increasingly common. Our aim was to investigate the referral patterns and associated details.

METHODS

We conducted an audit of 100 consecutive patients with LSCD who were referred to our service from 2011 to 2018. Patient demographics, geographical location, cause of LSCD, coexisting ocular diseases, best corrected visual acuity (BCVA), and extent of LSCD were recorded. The following two subgroups were further analyzed: (1) burns and (2) other causes of LSCD.

RESULTS

Out of the 100 patients (138 eyes), 70% were male, with a mean age of 45 years (SD 19). LSCD was unilateral in 62% of the cases. The most common ocular comorbidity was glaucoma, in 21 patients (33 eyes). Burns were the most frequent cause of referral (61%). The mean BCVA of the involved eye was 1.22 (SD 0.8) LogMAR, and total LSCD was present in 75 eyes (54%). There were statistically significant age, gender and eye-involved differences between the burns group and other causes group, mean 39 (SD 17) and 53 (SD 19) years (p < 0.001); 85% were men versus 48.7%, (p = 0.001); and 82% were unilateral versus 31% (p < 0.001), respectively.

CONCLUSIONS

LSCD was more common in men and usually unilateral. Overall, the main cause of LSCD was burns. There were significant differences between the burns group and other causes of LSCD group in terms of age, gender and unilateral involvement that may help to guide management decisions.

Outcomes of Ipsilateral Simple Limbal Epithelial Transplantation, Tenonectomy, Mitomycin and Amniotic Membrane Transplantation for Treatment of Recurrent Pterygium

PURPOSE

To report on the outcomes of recurrent pterygium treated by ipsilateral simple limbal epithelial transplantation (SLET), mitomycin, tenonectomy, and amniotic membrane transplantation.

METHODS

A retrospective, interventional study was conducted including all patients with recurrent pterygium who underwent SLET surgery under a single surgeon using ipsilateral donor tissue with a minimum 6-month follow-up at Toronto Western Hospital, Canada. Outcome measures included the following: recurrence rates, best spectacle-corrected visual acuity, and postoperative complications.

RESULTS

Ten eyes of 10 patients, aged 60.7 ± 18.5 years (range 23-79) with a mean follow-up time of 15.2 ± 10.0 months of which 50% (n = 5) were men, were included. Eight eyes (80%) had a history of 2 or less pterygium operations. Two patients had 3 and 5 previous pterygium operations, respectively. Concurrent limbal stem cell disease was noted in 6 eyes (60%). Average number of pterygium recurrences per eye was 1.9 ± 1.3 (range 1-5). Mean pre-op best-corrected visual acuity was 0.5 LogMAR (Snellen equivalent 20/60, range 20/20 to counting fingers). Best-corrected visual acuity remained the same or improved in 6 eyes (60%). Recurrence was noted in 1 eye (10%) with a history of 5 previous pterygium excisions and remained stable at the last follow-up. No patients required a second operation.

CONCLUSIONS

Ipsilateral SLET with mitomycin, tenonectomy, and amniotic membrane transplantation is a novel technique to address recurrent pterygium. Concurrent limbal stem cell diseases are often present. Initial results demonstrate low recurrence. Visual improvement is modest. Stabilization of the ocular surface to improve vision is possible.

Glueless Simple Limbal Epithelial Transplantation: The Report of the First 2 Cases

PURPOSE

To assess the anatomic and visual results of the modified glueless simple limbal epithelial transplantation (G-SLET) in the treatment of unilateral limbal stem cell deficiency (LSCD).

METHODS

This is a retrospective analysis of 2 patients who received G-SLET for corneal reepithelization after unilateral eye burn. After the recipient bed preparation on the eye with LSCD, radial symmetrical superficial incisions were applied to the corneal periphery. Next, short (1 mm) slightly oblique or horizontal tunnels were formed in every incision. The precut limbal pieces from the healthy eye were inserted into the tunnels with a scleral portion forward. At the end of surgery, the amniotic membrane was sutured to the sclera outside the corneal limbus with a single running suture.

RESULTS

Slit lamp examination in the early postoperative period revealed that transplanted limbal pieces remained in place and were visible through the semitransparent amniotic membrane. The donor's eye had a small scar and light subconjunctival hemorrhage. Early and late postoperative periods were uneventful. Twelve months after surgery, the LSCD-affected cornea was entirely covered with tight and semitransparent epithelium. The donor's eye exhibited a small scar on the site of the biopsy. Visual improvement was achieved in case 2, but the vision did not improve due to the presence of a mature cataract in case 1.

CONCLUSIONS

Modified G-SLET technique could be an option for LSCD treatment in patients with unilateral eye disease in cases when fibrin glue is not available for the surgeon.

Innovative technique of mini-simple limbal epithelial transplantation in pediatric patients

In this article, we introduce a modified technique of minor ipsilateral simple limbal epithelial transplantation (mini-SLET) in pediatric patients of limbal stem cell deficiency (LSCD). Two children with unilateral partial LSCD underwent the innovative technique of mini-SLET, where harvested limbal tissues were placed over the raw cornea and were covered with amniotic membrane. Both patients were followed till 9 months. Both cases showed favorable outcome and uneventful recovery. Results were comparable with the classical technique. This innovative modification of mini-SLET is safe, feasible, and an effective alternative with favorable visual outcome especially in pediatric population. It can be a breakthrough for LSCD management in developing countries with limited resources.

Current perspectives of limbal-derived stem cells and its application in ocular surface regeneration and limbal stem cell transplantation

Limbal stem cells are involved in replenishing and maintaining the epithelium of the cornea. Damage to the limbus due to chemical/physical injury, infections, or genetic disorders leads to limbal stem cell deficiency (LSCD) with partial or total vision loss. Presently, LSCD is treated by transplanting limbal stem cells from the healthy eye of the recipient, living-related, or cadaveric donors. This review discusses limbal-derived stem cells, the importance of extracellular matrix in stem cell niche maintenance, the historical perspective of treating LSCD, including related advantages and limitations, and our experience of limbal stem cell transplantation over the decades.

Stem Cell Niche Microenvironment: Review

The cornea comprises a pool of self-regenerating epithelial cells that are crucial to preserving clarity and visibility. Limbal epithelial stem cells (LESCs), which live in a specialized stem cell niche (SCN), are crucial for the survival of the human corneal epithelium. They live at the bottom of the limbal crypts, in a physically enclosed microenvironment with a number of neighboring niche cells. Scientists also simplified features of these diverse microenvironments for more analysis in situ by designing and recreating features of different SCNs. Recent methods for regenerating the corneal epithelium after serious trauma, including burns and allergic assaults, focus mainly on regenerating the LESCs. Mesenchymal stem cells, which can transform into self-renewing and skeletal tissues, hold immense interest for tissue engineering and innovative medicinal exploration. This review summarizes all types of LESCs, identity and location of the human epithelial stem cells (HESCs), reconstruction of LSCN and artificial stem cells for self-renewal.

Stem Cells in the Path of Light, from Corneal to Retinal Reconstruction

The future of eye reconstruction invariably includes stem cells transplantation. Corneal limbus, corneal stroma, trabeculum, retinal cells, optic nerve, and all structures that are irreversibly damaged and have no means to be repaired or replaced, through conventional treatment or surgery, represent targets for stem cell reconstruction. This review tries to answer the question if there is any clinical validation for stem therapies, so far, starting from the cornea and, on the path of light, arriving to the retina. The investigation covers the last 10 years of publications. From 2385 published sources, we found 56 clinical studies matching inclusion criteria, 39 involving cornea, and 17 involving retina. So far, corneal epithelial reconstruction seems well validated clinically. Enough clinical data are collected to allow some form of standardization for the stem cell transplant procedures. Cultivated limbal epithelial stem cells (CLET), simple limbal epithelial transplant (SLET), and oral mucosa transplantation are implemented worldwide. In comparison, far less patients are investigated in retinal stem reconstructions, with lower anatomical and clinical success, so far. Intravitreal, subretinal, and suprachoroidal approach for retinal stem therapies face specific challenges.

Global Consensus on the Management of Limbal Stem Cell Deficiency

PURPOSE

In recent decades, the medical and surgical treatment of limbal stem cell deficiency (LSCD) has evolved significantly through the incorporation of innovative pharmacological strategies, surgical techniques, bioengineering, and cell therapy. With such a wide variety of options, there is a need to establish a global consensus on the preferred approaches for the medical and surgical treatment of LSCD.

METHODS

An international LSCD Working Group was established by the Cornea Society in 2012 and divided into subcommittees. Four face-to-face meetings, frequent email discussions, and teleconferences were conducted since then to reach agreement on a strategic plan and methods after a comprehensive literature search. A writing group drafted the current study.

RESULTS

A consensus in the medical and surgical management of LSCD was reached by the Working Group. Optimization of the ocular surface by eyelid and conjunctival reconstruction, antiinflammatory therapy, dry eye and meibomian gland dysfunction treatment, minimization of ocular surface toxicity from medications, topical medications that promote epithelialization, and use of a scleral lens is considered essential before surgical treatment of LSCD. Depending on the laterality, cause, and stage of LSCD, surgical strategies including conjunctival epitheliectomy, amniotic membrane transplantation, transplantation of limbal stem cells using different techniques and sources (allogeneic vs. autologous vs. ex vivo-cultivated), transplantation of oral mucosal epithelium, and keratoprosthesis can be performed as treatment. A stepwise flowchart for use in treatment decision-making was established.

CONCLUSIONS

This global consensus provides an up-to-date and comprehensive framework for the management of LSCD.

Efficacy and outcome of simple limbal epithelial transplantation for limbal stem cell deficiency verified by epithelial phenotypes integrated with clinical evaluation

PURPOSE

To evaluate the efficacy and outcome of simple limbal epithelial transplantation (SLET) for limbal stem cell deficiency (LSCD) using epithelial phenotype detection integrated with clinical manifestation.

METHODS

This prospective multicenter study included patients with LSCD who underwent autologous SLET (autoSLET) and living-related allogenic SLET (Lr-alloSLET). All patients were assessed by slit-lamp biomicroscopy, in vivo confocal microscopy (IVCM), and impression cytology with immunofluorescence staining (ICIF) before and after surgery. The criteria for success were the presence of a clinically non-conjunctivalized cornea and corneal epithelium detected by IVCM or ICIF. Otherwise, the case would be considered a failure. Visual improvement and risk factors for SLET failure were analyzed.

RESULTS

A total of 28 eyes of 26 patients (11 autoSLET and 17 Lr-alloSLET) were included. The median age was 53 years (range, 35-63), and the follow-up time was 29.5 months (range, 17.5-39.8). The overall survival rate was 89.3% at 2 years and 75.6% at 3 years with no difference between autoSLET and Lr-alloSLET (p = 0.24). Seven eyes subsequently underwent penetrating keratoplasty. Immunohistochemistry analysis showed that all corneal buttons had corneal epithelium and limbal stem cell markers. Visual improvement was achieved in both SLET groups (p < 0.001). Failed SLET developed between 5 and 32 months postoperatively. However, absolute risk factors for SLET failure were unidentified.

CONCLUSION

The efficacy of autoSLET and Lr-alloSLET for LSCD was excellent. Limbal explants can regenerate and restore the corneal surface while maintaining the characteristics of limbal stem cells as shown by epithelial phenotype detection and immunohistochemistry integrated with clinical evaluation.