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

Timeframe to Keratoplasty After Ocular Surface Stem Cell Transplantation

PURPOSE

The aim of this study is to report the actual time delay between ocular surface stem cell transplantation (OSST) and keratoplasty at a high-volume center for limbal stem cell deficiency (LSCD). Understanding expected timelines and reasons for any delays or deferrals can allow for more accurate expectation-setting discussions with prospective patients.

METHODS

A retrospective chart review was performed on all patients having undergone OSST between January 2013 and December 2022. Charts were reviewed to determine whether the need for keratoplasty was specified at the time of OSST planning. Parameters for these cases were then collected including underlying diagnoses, type of OSST performed, and time delay between OSST and keratoplasty (if performed). Results were then aggregated, and subgroup analysis was conducted.

RESULTS

A total of 219 eyes were included, of which, 128 eyes had initial intent for keratoplasty. Of these, 48% had keratoplasty within 6 months of OSST, 17% between 6 and 24 months, 5% beyond 2 years, and, interestingly, 30% had no subsequent keratoplasty. Most eyes with no eventual keratoplasty experienced unanticipated stromal clearing after OSST obviating the need for keratoplasty.

CONCLUSIONS

This is the first study to report realized time delay between OSST and keratoplasty at a large LSCD practice. Prospective patients can be counselled that 76% of compliant cases with initial intent for keratoplasty either had keratoplasty within 6 months or exhibited unanticipated stromal clearing after OSST alone. Patients with congenital aniridia or contact lens-related LSCD are more likely to have unanticipated stromal clearing.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prevalence of limbal stem cell deficiency at an academic referral center over a two-year period

Aim

To evaluate the prevalence and clinical characteristics of limbal stem cell deficiency (LSCD) in the setting of a tertiary referral cornea practice at an academic center.

Patient and methods

A retrospective chart review was performed to identify all unique medical record numbers (MRNs) presenting to a single cornea specialist (JHH) at the University of Minnesota during calendar years 2019 and 2020. Records were queried and confirmed for a diagnosis of LSCD. Clinical characteristics of identified patients, including demographics, etiology of LSCD, severity of LSCD, treatment, and best corrected visual acuity (BCVA) at final follow-up, were documented.

Results

In total 1436 unique MRNs were identified over the study period. There were 61 individuals (91 eyes) diagnosed with LSCD, resulting in a prevalence of 4.25% (95% CI, 3.33-5.42). Of 91 eyes, 60 eyes were bilateral (65.9%). Among all eyes, ocular surface burns were the most common etiology (18.7%) followed by iatrogenic or medicamentosa (15.4%). There were 51 eyes (56.0%) that underwent some form of transplantation. The median BCVA at final follow-up was Snellen 20/80 (range 20/20 to no light perception).

Conclusions

The prevalence of LSCD found at a cornea subspecialty tertiary referral center in our study was much higher than previously reported prevalence rates. This may reflect referral bias and potential underdiagnosis of LSCD in practices outside of subspecialty referral centers. The high prevalence rate in our study also suggests that LSCD patients are concentrated in subspecialty referral practices, with many having high morbidity disease. This constitutes a major health burden for these practices.

Evaluation of Limbal Stem Cell Transplant Success in Ocular Chemical Injury

OBJECTIVES

We evaluated limbal stem cell transplant success in limbal stem cell deficiency due to chemical injury at a tertiary eye care center in Turkey with a novel system for describing limbal stem cell deficiency, as developed by the Limbal Stem Cell Working Group.

MATERIALS AND METHODS

Medical records of 80 eyes of 80 patients after limbal stem cell transplant for limbal stem cell deficiency secondary to chemical injury were included, with patients grouped according to surgical procedure, ie, limbal autograft, limbal allograft, and cultivated limbal epithelial cell transplant. Surgical success was defined as improvement in postoperative year 1 of limbal stem cell deficiency stage.

RESULTS

Patients' mean age was 37.9 ± 15.7 years (range, 4-71 years). Male/female ratio was 2.4. Forty-five patients (56.3%) were injured with alkaline substance, and 16 (20%) with acid substance. Mean follow-up time was 60.3 ± 30.6 months (range, 6-118.6 months). Limbal autograft, allograft, and cultivated limbal epithelial cell transplants were performed in 58 (72.5%), 12 (15%), and 10 (12.5%) eyes, respectively. Intervals between injury and surgery in limbal autograft, limbal allograft, and cultivated limbal epithelial cell transplants were 43.3 ± 94.1 months (range, 0.5-592 months), 14.5 ± 10.6 months (range, 2.4-32.5 months), and 122.8 ± 158.9 months (range, 21.1-504 months),respectively (P = .02); and surgical success rates in each group were 65.5%, 41.7%, and 90%, respectively (P = .03). Overall surgical success rate was 65%.

CONCLUSIONS

Accurate determination of the limbal stem cell deficiency stage is crucial for proper evaluation of surgical success. Surgery type and interval between injury and surgery were the most important factors associated with higher surgical success rates. Despite the limited number of patients in the subgroups, the results were remarkable to emphasize the significance of a novel limbal stem cell deficiency scoring system.

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.

En Bloc Keratolimbal Allograft and Central Penetrating Keratoplasty: A Novel Surgical Technique in Severe Limbal Stem Cell Deficiency

PURPOSE

The purpose of this study was to present a novel surgical technique combining 360-degree keratolimbal allograft (KLAL) and simultaneous central keratoplasty termed en bloc KLAL with the central penetrating keratoplasty (PKP) performed in those cases with total limbal stem cell deficiency (LSCD) and corneal scars.

METHODS

Nine eyes of 9 patients underwent en bloc KLAL and central PKP between 2014 and 2016. All patients had bilateral total LSCD with total corneal opacity due to different etiologies. The exclusion criteria were previous limbal stem cell transplantation and the presence of active and uncontrolled ocular surface inflammation. The same donor globe was used for harvesting 360-degree KLAL and central PKP. The 1-piece integrity of the KLAL and PKP graft was preserved during the described technique. All patients received modified immunosuppressive regimens compatible with the Cincinnati solid organ transplantation protocol.

RESULTS

The average age of patients was 58.6 ± 18.6 years. The diagnosis was mustard gas keratopathy in 6, herpes simplex keratitis in 1, and severe acid chemical burn in 2 patients. Seven patients were male. An integrated ocular surface without epitheliopathy and a clear cornea was achieved in 8 patients (88.8%) with an average of 6.5 years in follow-up. The average best-corrected visual acuity was 1.89 ± 0.18 (20/1600) preoperatively which improved to 1.02 ± 0.64 (20/200) logMAR in the postoperative period. Endothelial immune rejection episodes were observed in 3 patients. KLAL rejection was not observed in any patient. One patient required repeat PKP due to corneal graft failure.

CONCLUSIONS

En bloc 360-degree KLAL and central PKP could simultaneously be performed in patients with total LSCD and corneal opacification.

Profile of biological characterizations and clinical application of corneal stem/progenitor cells

Corneal stem/progenitor cells are typical adult stem/progenitor cells. The human cornea covers the front of the eyeball, which protects the eye from the outside environment while allowing vision. The location and function demand the cornea to maintain its transparency and to continuously renew its epithelial surface by replacing injured or aged cells through a rapid turnover process in which corneal stem/progenitor cells play an important role. Corneal stem/progenitor cells include mainly corneal epithelial stem cells, corneal endothelial cell progenitors and corneal stromal stem cells. Since the discovery of corneal epithelial stem cells (also known as limbal stem cells) in 1971, an increasing number of markers for corneal stem/progenitor cells have been proposed, but there is no consensus regarding the definitive markers for them. Therefore, the identification, isolation and cultivation of these cells remain challenging without a unified approach. In this review, we systematically introduce the profile of biological characterizations, such as anatomy, characteristics, isolation, cultivation and molecular markers, and clinical applications of the three categories of corneal stem/progenitor cells.

Goals and Challenges of Stem Cell-Based Therapy for Corneal Blindness Due to Limbal Deficiency

Corneal failure is a highly prevalent cause of blindness. One special cause of corneal failure occurs due to malfunction or destruction of the limbal stem cell niche, upon which the superficial cornea depends for homeostatic maintenance and wound healing. Failure of the limbal niche is referred to as limbal stem cell deficiency. As the corneal epithelial stem cell niche is easily accessible, limbal stem cell-based therapy and regenerative medicine applied to the ocular surface are among the most highly advanced forms of this novel approach to disease therapy. However, the challenges are still great, including the development of cell-based products and understanding how they work in the patient's eye. Advances are being made at the molecular, cellular, and tissue levels to alter disease processes and to reduce or eliminate blindness. Efforts must be coordinated from the most basic research to the most clinically oriented projects so that cell-based therapies can become an integrated part of the therapeutic armamentarium to fight corneal blindness. We undoubtedly are progressing along the right path because cell-based therapy for eye diseases is one of the most successful examples of global regenerative medicine.