Corticosteroid has been used for the treatment after phototherapeutic keratectomy (PRK). Dexamethasone, a potent steroid can retard the corneal epithelial healing rate and has numerous serious complications, especially glaucoma. Loteprednol, a new generation of corticosteroid has less potency than dexamethasone and was proposed to has less side effect regarding intraocular pressure (IOP) elevation. Therefore, Investigators would like to compare the effect of dexamethasone and loteprednol on corneal epithelial healing rate after PRK and risk of glaucoma.

Inclusion Criteria:

• the patient with epithelial defect after phototherapeutic keratectomy

Exclusion Criteria:

• the patient with systemic disease such as diabetes and connective tissue disease
• the patient with ocular surface disease such as dry eye and recurrent corneal erosion