Usage of topical insulin for the treatment of diabetic keratopathy, including corneal epithelial defects

BACKGROUND: Diabetic keratopathy (DK) occurs in 46%-64% of patients with diabetes and requires serious attention. In patients with diabetes, the healing of corneal epithelial defects or ulcers takes longer than in patients without diabetes. Insulin is an effective factor in wound healing. The ability of systemic insulin to rapidly heal burn wounds has been reported for nearly a century, but only a few studies have been performed on the effects of topical insulin (TI) on the eye. Treatment with TI is effective in treating DK. AIM: To review clinical and experimental animal studies providing evidence for the efficacy of TI to heal corneal wounds. METHODS: National and international databases, including PubMed and Scopus, were searched using relevant keywords, and additional manual searches were conducted to assess the effectiveness of TI application on corneal wound healing. Journal articles published from January 1, 2000 to December 1, 2022 were examined. The relevancy of the identified citations was checked against predetermined eligibility standards, and relevant articles were extracted and reviewed. RESULTS: A total of eight articles were found relevant to be discussed in this review, including four animal studies and four clinical studies. According to the studies conducted, TI is effective for corneal re-epithelialization in patients with diabetes based on corneal wound size and healing rate. CONCLUSION: Available animal and clinical studies have shown that TI promotes corneal wound healing by several mechanisms. The use of TI was not associated with adverse effects in any of the published cases. Further studies are needed to enhance our knowledge and understanding of TI in the healing of DK.