Simultaneous deep anterior lamellar keratoplasty and limbal allograft in bilateral limbal stem cell deficiency

TACSTD2 in gelatinous drop-like corneal dystrophy: variant functional analysis and expression in the cornea after limbal stem cell transplantation

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive eye disease. GDLD is characterized by the loss of barrier function in corneal epithelial cells (CECs) and amyloid deposition due to pathogenic variants in the TACSTD2 gene. Limbal stem cell transplantation (LSCT) has been suggested as an effective therapeutic alternative for patients with GDLD. However, despite LSCT, amyloid deposition recurs in some patients. The pathogenesis of recurrence is poorly studied. We present the case of a patient with GDLD. Genetic analysis revealed a homozygous deletion, NM_002353.3:c.653del, in the TACSTD2 gene. Functional analysis in a cell model system revealed the loss of the transmembrane domain and subcellular protein mislocalization. The patient with GDLD underwent direct allogeneic LSCT with epithelial debridement followed by deep anterior lamellar keratoplasty 10 months later due to amyloid deposition and deterioration of vision. Taken together, the results of transcriptome analysis and immunofluorescence staining of post-LSCT corneal sample with amyloid deposits obtained during keratoplasty demonstrated complete restoration of wild-type TACSTD2 expression, indicating that donor CECs replaced host CECs. Our study provides experimental evidence that amyloid deposition can recur after LSCT despite complete restoration of wild-type TACSTD2 expression.

Future directions in managing aniridia-associated keratopathy

Congenital aniridia is a panocular disorder that is typically characterized by iris hypoplasia and aniridia-associated keratopathy (AAK). AAK results in the progressive loss of corneal transparency and thereby loss of vision. Currently, there is no approved therapy to delay or prevent its progression, and clinical management is challenging because of phenotypic variability and high risk of complications after interventions; however, new insights into the molecular pathogenesis of AAK may help improve its management. Here, we review the current understanding about the pathogenesis and management of AAK. We highlight the biological mechanisms involved in AAK development with the aim to develop future treatment options, including surgical, pharmacological, cell therapies, and gene therapies.

Genetic predisposition to ocular surface disorders and opportunities for gene-based therapies

The ocular surface, comprised of the corneal and conjunctival epithelium, innervation system, immune components, and tear-film apparatus, plays a key role in ocular integrity as well as comfort and vision. Gene defects may result in congenital ocular or systemic disorders with prominent ocular surface involvement. Examples include epithelial corneal dystrophies, aniridia, ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, xeroderma pigmentosum (XP), and hereditary sensory and autonomic neuropathy. In addition, genetic factors may interact with environmental risk factors in the development of several multifactorial ocular surface disorders (OSDs) such as autoimmune disorders, allergies, neoplasms, and dry eye disease. Advanced gene-based technologies have already been introduced in disease modelling and proof-of-concept gene therapies for monogenic OSDs. For instance, patient-derived induced pluripotent stem cells have been used for modelling aniridia-associated keratopathy (AAK), XP, and EEC syndrome. Moreover, CRISPR/Cas9 genome editing has been used for disease modelling and/or gene therapy for AAK and Meesmann's epithelial corneal dystrophy. A better understanding of the role of genetic factors in OSDs may be helpful in designing personalized disease models and treatment approaches. Gene-based approaches in monogenic OSDs and genetic predisposition to multifactorial OSDs such as immune-mediated disorders and neoplasms with known or possible genetic risk factors has been seldom reviewed. In this narrative review, we discuss the role of genetic factors in monogenic and multifactorial OSDs and potential opportunities for gene therapy.

Preparing the Ocular Surface for a Boston Keratoprosthesis Type 1 Through En Bloc Minor Salivary Gland Transplantation and Mucous Membrane Grafting in End-Stage Stevens-Johnson Syndrome

PURPOSE

This case describes the successful visual restoration of a patient with end-stage Stevens-Johnson syndrome (SJS) with a severely keratinized ocular surface.

METHODS

This study is a case report.

RESULTS

A 67-year-old man with SJS secondary to allopurinol sought visual rehabilitation options. His ocular surface was severely compromised from sequelae of chronic SJS, leaving him with light perception vision bilaterally. The left eye was completely keratinized with severe ankyloblepharon. The right eye had failed penetrating keratoplasty, limbal stem cell deficiency, and a keratinized ocular surface. The patient declined both a Boston type 2 keratoprosthesis and a modified osteo-odonto keratoprosthesis. Therefore, a staged approach was pursued with (1) systemic methotrexate to control ocular surface inflammation, (2) minor salivary gland transplant to increase ocular surface lubrication, (3) lid margin mucous membrane graft to reduce keratinization, and finally, (4) Boston type 1 keratoprosthesis for visual restoration. After minor salivary gland transplant and mucous membrane graft, the Schirmer score improved from 0 mm to 3 mm with improvement in ocular surface keratinization. This approach successfully restored the vision to 20/60, and the patient has retained the keratoprosthesis for over 2 years.

CONCLUSIONS

Sight restoration options are limited in patients with end-stage SJS with a keratinized ocular surface, aqueous and mucin deficiency, corneal opacification, and limbal stem cell deficiency. This case demonstrates successful ocular surface rehabilitation and vision restoration in such a patient through a multifaceted approach that resulted in successful implantation and retention of a Boston type 1 keratoprosthesis.

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.

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.

A Review of the Diagnosis and Treatment of Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) can cause significant corneal vascularization and scarring and often results in serious visual morbidity. An early and accurate diagnosis can help prevent the same with a timely and appropriate intervention. This review aims to provide an understanding of the different diagnostic tools and presents an algorithmic approach to the management based on a comprehensive clinical examination. Although the diagnosis of LSCD usually relies on the clinical findings, they can be subjective and non-specific. In such cases, using an investigative modality offers an objective method of confirming the diagnosis. Several diagnostic tools have been described in literature, each having its own advantages and limitations. Impression cytology and in vivo confocal microscopy (IVCM) aid in the diagnosis of LSCD by detecting the presence of goblet cells. With immunohistochemistry, impression cytology can help in confirming the corneal or conjunctival source of epithelium. Both IVCM and anterior segment optical coherence tomography can help supplement the diagnosis of LSCD by characterizing the corneal and limbal epithelial changes. Once the diagnosis is established, one of various surgical techniques can be adopted for the treatment of LSCD. These surgeries aim to provide a new source of corneal epithelial stem cells and help in restoring the stability of the ocular surface. The choice of procedure depends on several factors including the involvement of the ocular adnexa, presence of systemic co-morbidities, status of the fellow eye and the comfort level of the surgeon. In LSCD with wet ocular surfaces, autologous and allogeneic limbal stem cell transplantation is preferred in unilateral and bilateral cases, respectively. Another approach in bilateral LSCD with wet ocular surfaces is the use of an autologous stem cell source of a different epithelial lineage, like oral or nasal mucosa. In eyes with bilateral LSCD with significant adnexal issues, a keratoprosthesis is the only viable option. This review provides an overview on the diagnosis and treatment of LSCD, which will help the clinician choose the best option amongst all the therapeutic modalities currently available and gives a clinical perspective on customizing the treatment for each individual case.

Mini-conjunctival autograft combined with deep anterior lamellar keratoplasty for chronic sequelae of severe unilateral chemical burn: A case report

Introduction and importance

This case describes a novel technique combining a mini-conjunctival limbal autograft (CLAU) with a deep anterior lamellar keratoplasty (DALK) in a case of chemical injury sequelae.

Case presentation

A 19-year-old female presented with total limbal stem cell deficiency (LSCD) and a vascularized corneal scar in the visual axis of the left eye, 4 years following a chemical injury. In order to treat the LSCD and simultaneously visually rehabilitate the patient, a mini-CLAU with DALK was carried out. Two separate one clock-hour CLAUs were harvested from the right eye and secured in the left. The graft was clear in the initial postoperative period and maintained its clarity over 15 months of follow period with a visual acuity of 20/30 with scleral contact lenses. The mini-CLAUs sustained a stable and well epithelialized corneal surface during the same period.

Clinical discussion

The use of the mini-CLAUs instead of the traditional CLAU circumvents the complication of an iatrogenic LSCD in the donor eye as the size of the donor grafts is smaller (1–2 clock hours versus 6–8 clock hours). Despite the smaller size, these grafts are efficacious in maintaining a well epithelialized corneal surface even in cases of total LSCD. The autologous nature of the graft defers the need for immunosuppression and its peripheral location facilitates ease of the surgical technique when combined with a keratoplasty.

Conclusion

This novel single-staged procedure is an effective technique to reestablish a stable ocular surface and to visually rehabilitate cases of chronic chemical injury with good long-term outcomes.

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Severe ocular burns need both corneal and limbal transplantation.

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Anterior lamellar keratoplasty is preferred over penetrating grafts.

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Mini-conjunctival limbal grafts can be obtained safely from the healthy fellow eye.

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The need for long-term systemic immunosuppression is minimized in this approach.

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This combined technique leads to good and sustainable functional recovery.

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.

Femtosecond Laser-Assisted Keratolimbal Allograft Transplantation for the Treatment of Total Limbal Stem Cell Deficiency

PURPOSE

To investigate the surgical procedure and therapeutic efficacy of femtosecond (FS) laser-assisted keratolimbal allograft (KLAL) transplantation in the treatment of eyes with total limbal stem cell deficiency.

METHODS

Ten eyes from 10 patients who underwent FS laser-assisted KLAL transplantation were enrolled. The best-corrected visual acuity (BCVA), ocular surface stability, corneal transparency, and postoperative complications were recorded.

RESULTS

The keratolimbal grafts prepared using the FS laser were even in thickness and width. After the surgery, glucocorticoid and tacrolimus eye drops were administered locally to the eyes with concentration gradients, and a medium dose was prescribed for maintenance. Within the mean follow-up period of 16.8 ± 7.3 months, 9 of 10 eyes (90.0%) maintained a stable ocular surface and showed significant improvements in corneal transparency and BCVA. Persistent corneal edema only occurred in one eye because of repeated epithelial defects, and the BCVA of this eye did not improve. Confocal microscopy revealed activated dendritic cells in the Bowman membrane at the limbus, but they were always low in density with small dendritic processes. No acute immune rejection, cataracts, or elevation of intraocular pressure were detected.

CONCLUSIONS

The FS laser-assisted KLAL technique can produce ring-shaped grafts with an even depth and width, resulting in a stable ocular surface and good visual prognosis. After surgery, glucocorticoids and potent immunosuppressive eye drops were administered locally with concentration gradients and effectively inhibited acute immune rejection.

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

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

Deep anterior lamellar keratoplasty: A surgeon's guide

Purpose

To review and highlight important practical aspects of deep anterior lamellar keratoplasty (DALK) surgery and provide some useful tips for surgeons wishing to convert to this procedure from the conventional penetrating keratoplasty (PK) technique.

Methods

In this narrative review, the procedure of DALK is described in detail. Important pre, intra, and postoperative considerations are discussed with illustrative examples for better understanding. A comprehensive literature review was conducted in PubMed/Medline from January 1995 to July 2017 to identify original studies in English language regarding DALK. The primary endpoint of this review was the narrative description of surgical steps for DALK, its pitfalls, and management of common intraoperative complications.

Results

A standard DALK procedure can be successfully performed taking into consideration factors such as age, ophthalmic co-morbidities, status of the crystalline lens, retina, and intraocular pressure. Careful trephination and dissection of the host cornea employing appropriate technique (such as big bubble technique, manual dissection, visco-dissection, etc.) suitable for the specific case is important to achieve good postoperative outcomes. Prompt identification of intraoperative complications such as double bubble, micro and macroperforations, etc. are vital to change the management strategies.

Conclusion

Although there is a steep learning curve for DALK procedure, considering details and having insight into the management of intraoperative issues facilitates learning and reduces complication rates.

Long-term Outcomes of Ocular Surface Stem Cell Allograft Transplantation

PURPOSE

To investigate the long-term outcomes of ocular surface stem cell allograft transplantation (OSST) in patients with total limbal stem cell deficiency (LSCD) owing to various etiologies with a follow-up ≥ 5 years.

DESIGN

Retrospective interventional cohort.

METHODS

Setting: Single tertiary referral hospital.

STUDY POPULATION

Patients who had (1) presence of total LSCD, (2) surgical treatment with at least 1 allograft OSST procedure, and (3) minimum follow-up ≥ 5 years after OSST.

INTERVENTION

All patients underwent allograft OSST from March 1998 to June 2009. All patients received systemic immunosuppression.

MAIN OUTCOME MEASURES

Ocular surface stability, best-corrected visual acuity (BCVA).

RESULTS

A total of 165 eyes of 110 patients fulfilled the inclusion criteria with a mean follow-up period of 109.22 ± 35.7 months or approximately 9.1 years (range 5.2-17.7 years). Ocular surface stability was achieved in 72.7% (120/165) of eyes at last follow-up, while 15.2% (25/165) maintained an improved ocular surface and 12.1% (20/165) developed total surface failure. Additional OSST surgery was necessary in 30.9% (51/165 eyes) to maintain a stable ocular surface. There was ≥ 2 lines BCVA improvement in 62.1%, no change in 7.7%, and a worsened BCVA in 18.6% at last follow-up.

CONCLUSIONS

With proper immunosuppression and repeat procedure in case of failure, allograft OSST can provide true long-term ocular surface stability and successful visual outcomes.

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).

Gelatinous drop-like corneal dystrophy: a review

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive form of corneal dystrophy characterised by subepithelial and stromal amyloid deposits. It is relatively common in Japan. It usually presents in the first two decades of life with subepithelial nodular lesions that later coalesce to form mulberry-like opacities. Although various surgical modalities have been attempted, recurrence remains a major challenge.

Histopathology Findings of Corneal Buttons in Congenital Aniridia Patients

PURPOSE

To evaluate the corneal button of primary penetrating keratoplasty of patients diagnosed with congenital aniridia. The study took place at the Instituto Universitario Barraquer and the Centro de Oftalmología Barraquer.

METHODS

A retrospective analysis of cases diagnosed with congenital aniridia was carried out. We analyzed 13 corneal buttons of 11 eyes with congenital aniridia. We only included those patients who underwent penetrating keratoplasty for the first time. The corneal buttons were analyzed for histological characteristics of the presence of vascularization, the presence or not of Bowman's layer, the thickness of the stroma and Descemet's membrane, and endothelium layer alterations.

RESULTS

We found alterations in the epithelium and stroma in all patients, although this loss of architecture was not seen in Descemet's membrane and the endothelial population.

CONCLUSION

Patients with advanced congenital aniridic keratopathy may be good candidates for deep or superficial anterior lamellar keratoplasty for the preservation of normal endothelium and Descemet's membrane, along with limbal stem cell transplantation, to address epithelial and stromal pathology.