The role of topical insulin in ocular surface restoration: A review

Corneal epithelial defects are one of the most common ocular disorders. Restoring corneal integrity is crucial to reduce pain and regain function, but in cases of neurotrophic or desensitized corneas, healing can be significantly delayed. Treating neurotrophic corneas is challenging for ophthalmologists, and surgical intervention is often indicated to manage refractory cases that are unresponsive to medical therapy. Over the last decade, as more expensive therapeutics reach the market, topical insulin has returned to the forefront as an affordable option to improve corneal wound healing. There is still a paucity of data on the use and the efficacy of topical insulin, with no consensus regarding its indications, preparation, or posology. Here we review the literature on topical insulin for corneal and ocular surface pathologies, with a focus on the current evidence, its mechanisms of action, and its safety profile. Additionally, we share our experience in the field and provide a potential framework for future research.

Ocular Surface Homeostasis After Scleral Lens Usage

OBJECTIVES

The aim of this prospective study is to examine the effects of 5 hours of well-fitted, mini-scleral contact lens (mini-SL) wear on the tear film cytokine expression in healthy eyes.

METHODS

Twenty-three healthy participants were included in the study. One eye of each participant was selected at random, and a mini-SL measuring 16.5 mm in diameter was fitted by an experienced contact lens specialist. The contact lens remained in place for 5 hours. Precorneal tear fluid was collected using capillary tubes at three different time points: baseline before SL insertion (T0), after 5 hours of SL wear (T1), and 3 hours after SL removal (T2). The concentration of 40 inflammatory cytokines at the three different time points was determined using multiplex bead assay.

RESULTS

Mini-scleral lens wear did not result in significant changes in the cytokine-to-protein ratio after 5 hours of wear on a healthy eye.

CONCLUSIONS

Although a well-fitted mini-SL reduces the rate at which the precorneal tear film is refreshed, 5 hours of lens wear did not appear to significantly affect the tears cytokine-to-protein ratio, suggesting that scleral lenses have minimal impact on corneal cytokine expression.

Outcomes of Human Leukocyte Antigen-Matched Allogeneic Cultivated Limbal Epithelial Transplantation in Aniridia-Associated Keratopathy-A Single-Center Retrospective Analysis

PURPOSE

To assess the efficacy and safety of human leukocyte antigen-matched allogeneic cultivated limbal epithelial stem cell grafts in the treatment of aniridia-associated keratopathy (AAK).

METHODS

Six eyes of 6 patients with severe AAK received an allogeneic stem cell graft between January 2010 and March 2017. Anatomical and functional results were assessed at 6 months, 1 year, 2 years, and the final follow-up visit available. Safety analysis was performed by considering all perioperative and postoperative adverse events and additional surgeries required during the follow-up period.

RESULTS

The mean follow-up was 53.6 months (range 24-104 months). In most patients (80%), there was an early improvement of the keratopathy postoperatively, which slowly regressed during longer follow-up. At the final follow-up, 4 of the eyes were graded as failure and 1 eye was graded as partial success. Grading the sixth eye was not possible because of an adverse event. None of the patients maintained a total anatomical success in the long-term. Only 1 patient maintained a modest improvement in best-corrected visual acuity from hand motion to counting fingers. Four serious adverse events were recorded in 2 patients.

CONCLUSIONS

Severe AAK remains a challenging condition to manage. Transplantation of allogenic ex vivo cultivated limbal stem cells may provide a temporary improvement in ocular surface stability, but anatomical and functional results are poor in the long-term. The eyes are prone to adverse events, and any surgical treatment should take this into consideration.

Ethical issues in living-related corneal tissue transplantation

The cornea was the first human solid tissue to be transplanted successfully, and is now a common procedure in ophthalmic surgery. The grafts come from deceased donors. Corneal therapies are now being developed that rely on tissue from living-related donors. This presents new ethical challenges for ophthalmic surgeons, who have hitherto been somewhat insulated from debates in transplantation and donation ethics. This paper provides the first overview of the ethical considerations generated by ocular tissue donation from living donors and suggests how these might be addressed in practice. These are discussed in the context of a novel treatment for corneal limbal stem cell deficiency. This involves limbal cell grafts which are transplanted, either directly or after ex vivo expansion, onto recipient stem cell-deficient eyes. Where only one eye is diseased, the unaffected eye can be used as a source of graft tissue. Bilateral disease requires an allogenic donation, preferably from a genetically related living donor. While numerous papers have dealt with the theory, surgical approaches and clinical outcomes of limbal stem cell therapies, none has addressed the ethical dimensions of this form of tissue donation.

A method for quantifying limbal stem cell niches using OCT imaging

Aims

To evaluate the efficacy of Fourier domain-optical coherence tomography (FD-OCT) in imaging and quantifying the limbal palisades of Vogt and to correlate these images with histological findings.

Methods

The superior and inferior limbal region of both eyes of 50 healthy volunteers were imaged by FD-OCT. Images were processed and analysed using Matlab software. In vitro immunofluorescent staining of a cadaveric donor limbus was analysed to correlate the presence of stem cells in the visualised structures.

Results

FD-OCT could successfully visualise limbal crypts and the palisades of Vogt in the limbus region. Fluorescent labelling confirmed the presence of stem cells in these structures. The mean palisade ridge width (Δ_PR) and the mean interpalisade epithelial rete peg width (Δ_ERP) were both of the order of 72 μm, leading to a palisade density (PD) of about 7.4 palisades/mm. A significant difference in Δ_PR, Δ_ERP and PD was seen between the inferior and superior sides of the right eye and the superior sides of the left and right eye(p<0.05.). A significant influence of iris colour on parameters Δ_PR, Δ_ERP and PD was found, and of age on PD and Δ_ERP (p<0.05).

Conclusions

In vivo OCT imaging is a safe and effective modality to image the limbus and can be used to visualise the palisades of Vogt. Image processing using Matlab software enabled quantification and density calculation of imaged limbal palisades of Vogt. This technique may enhance targeted limbal biopsies for transplantation.