INS and Keratoconjunctivitis sicca: In recent years, several clinical studies have been performed to further explore the efficacy of topical insulin in patients with refractory neurotrophic keratopathy [22, 23], refractory persistent epithelial defects and dry eye in DM [24–26], thus suggesting that insulin eye drops are potential targeted drugs for nerve impairment and corneal epithelial lesions.