A prospective randomized double-blind controlled trial will be conducted. The informed consent of each patient will be obtained prior to the procedure.

All patients will undergo a classic PRK procedure

Patients will be instructed to use eye drops blindly in both eyes at a frequency of six times daily:

• In one eye: Insulin drops formulated by combining regular human insulin with artificial tears containing polyethylene glycol (PEG 400) 0,25% at a concentration of 1 unit per milliliter.
• In the other eye: Placebo drops containing only artificial tears. For the double-blind trial, two identical vials will be provided to each patient: one labeled R (for the right eye) and one labeled L (for the left eye). Using the bloc randomization method, the pharmacy will be the only entity aware of the composition of each vial, ensuring that 50% of patients use insulin drops in the right eye and 50% in the left eye.

Every week the drops will be prepared one day prior to the PRK procedure and will be stored in a refrigerator, to be used within one week of their preparation date.

Patients will be examined by two ophthalmology residents on days 2 and 4 post-operatively.

The size of the epithelial defect in both eyes will be measured using the ImageJ software. Thus, the primary outcome of the study is the ulceration closure rate: the smaller the defect, the faster the epithelial healing is.

Additionally, a comparison of subjective symptoms reported by the patient in each eye will be recorded.

Inclusion Criteria:

• Myopic or astigmatic patient undergoing excimer laser PRK

Exclusion Criteria:

• diabetes mellitus prior ocular surgery ocular surface disease (including dry eye disease, history of herpetic keratitis) previous ocular trauma use of systemic corticosteroids