Evaluation of Limbal Stem Cell Transplant Success in Ocular Chemical Injury

Advances in Regenerative Medicine, Cell Therapy, and 3D Bioprinting for Corneal, Oculoplastic, and Orbital Surgery

Advances in regenerative medicine, cell therapy, and 3D bioprinting are reshaping the landscape of ocular surgery, offering innovative approaches to address complex conditions affecting the cornea, ocular adnexal structures, and the orbit. These technologies hold the potential to enhance treatment precision, improve functional outcomes, and address limitations in traditional surgical and therapeutic interventions.The cornea, as the eye's primary refractive and protective barrier, is particularly well-suited for regenerative approaches due to its avascular and immune-privileged nature. Cell-based therapies, including limbal stem cell transplantation as well as stromal keratocyte and corneal endothelial cell regeneration, are being investigated for their potential to restore corneal clarity and function in conditions such as limbal stem cell deficiency, keratoconus, and endothelial dysfunction. Simultaneously, 3D bioprinting technologies are enabling the development of biomimetic corneal constructs, potentially addressing the global shortage of donor tissues and facilitating personalized surgical solutions.In oculoplastic and orbital surgery, regenerative strategies and cell therapies are emerging as possible alternatives to conventional approaches for conditions such as eyelid defects, meibomian gland dysfunction, and Graves' orbitopathy. Stem cell-based therapies and bioengineered scaffolds are showing potential in restoring lacrimal glands' function as well as reconstructing complex ocular adnexal and orbital structures. Moreover, 3D-printed orbital implants and scaffolds offer innovative solutions for repairing traumatic, post-tumor resection, and congenital defects, with the potential for improved biocompatibility and precision.Molecular and gene-based therapies, including exosome delivery systems, nanoparticle-based interventions, and gene-editing techniques, are expanding the therapeutic arsenal for ophthalmic disorders. These approaches aim to enhance the efficacy of regenerative treatments by addressing underlying pathophysiological mechanisms of diseases. This chapter provides an overview of these advancements and the challenges of translating laboratory discoveries into effective therapies in clinical practice.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Precision of limbal ischemia evaluation in ocular chemical injuries with anterior segment optical coherence tomography angiography

PURPOSE

To evaluate the limbal ischemia objectively in ocular surface chemical injuries by using anterior segment optical coherence tomography angiography (AS-OCTA).

METHODS

In this cross-sectional study, acute ocular surface chemical injury patients with less than 1 week injury history were enrolled. Demographic data of the patients were noted, and detailed ophthalmological examination with Dua classification was performed. AS photographs and AS-OCTA images were obtained and used for the assessment of limbal ischemia. To visualize the limbal vasculature, the device was focused manually to get a sharp image for all 4 quadrants of the limbus. The absence of vasculature was regarded as "ischemia," and the amount of the ischemia was defined in clock hours. The limbal ischemia detected in clinical evaluation with biomicroscopy was compared with the AS-OCTA detected ischemia amount to make a conclusion for the correlation.

RESULTS

Nineteen eyes of 18 patients with acute ocular surface chemical injury were enrolled to the study (2 female, 16 male). The mean age was 35.1 ± 10 (18-55), and the mean best corrected visual acuity was 0.75 ± 1 (0.1-3.1) LogMAR. The causative agents were acid in 6 and alkaline in 12 patients. Limbal ischemia detected by using AS-OCTA was greater ((5.8 ± 2.6 (2-10) clock hours) than that detected in biomicroscopy (4.8 ± 2.4 (2-12) clock hours). The difference was statistically significant (p < 0.0005).

CONCLUSION

AS-OCTA has a significant importance on limbal vascularity visualization; therefore, its use for more objective and sensitive evaluation of limbal ischemia in ocular surface chemical injuries seems to have a crucial impact. AS-OCTA images may reveal the extension of limbal ischemia more precisely than clinical evaluation with biomicroscopy. However, future studies with higher number of patients are needed to come to a specific conclusion.