Persistent epithelial defect (PED) management can be challenging. First line of treatment includes lubrication, bandage contact lenses and punctal plugs. The second line of treatment includes autologous serum (AS). Topical insulin has been shown to be safe for topical use and improve corneal epithelial healing. Therefore, a controlled clinical trial (control group with current standard treatment, ie, AS) multicentre, randomised and with a blind third observer will be conducted to evaluate the efficacy and safety of the use of insulin eye-drops in the treatment of PED.

A preselection of patients with epithelial defect after 1 week of treatment will be made and blood tests will be obtained in order to dispense AS if necessary. After 2 weeks of standard treatment, if the PED persists and the patient meets criteria, patients will be enrolled after signing an informed consent form. Patients will be randomly allocated to receive either insulin (1 UI/mL, 4 times a day) or AS (20%, 5–6 times a day) eye-drops for 3 months. 234 patients will be included, 117 in each treatment group. The main variable (PED size) will be obtained from slit-lamp photographs, an objective and easily quantifiable variable which will be evaluated by a blinded investigator (third observer). Patients will be examined every 3–5 days until week 4 of study treatment and once a week until 6 weeks, to continue with a visit every 2 weeks until reaching 3 months of follow-up. Primary endpoints are: complete epithelialisation, epithelialisation rate (initial defect area/days until epithelialisation) and time until complete closure.

Ethical approval has been obtained from Hospital Clinico San Carlos in Madrid and Agencia Española del Medicamento y Productos Sanitarios (AEMPS). The findings will be disseminated in peer-reviewed publications and presentations at meetings.

EudraCT 2022-003589-19.