LASIK and the ocular surface.

Wound healing after LASIK sometimes compromises homeostasis of the ocular surface. Diffuse lamellar keratitis is a post-LASIK inflammatory condition in the interface that appears during the first week after LASIK. The etiology of diffuse lamellar keratitis is unknown, but the association with allergic reaction to detergent, bacteria, and other chemicals is suspected. The condition is mostly self-limiting. Topical and/or oral corticosteroids may be effective against stage 2 disease, whereas flap lift and irrigation might be required in stage 3. Epithelial ingrowth occurs in about 1% of LASIK eyes. Although most cases heal spontaneously, some require surgical removal. There are 2 known mechanisms for epithelial ingrowth: epithelial invasion and epithelial implantation. Epithelial invasion grows in 2 distinct ways--outside invasion and flap epithelial invasion. The latter type is often seen after enhancement and may be treatment resistant. Patients with compromised attachment of corneal epithelium before LASIK may develop recurrent corneal erosion, which sometimes requires phototherapeutic keratectomy. Subepithelial opacity after viral infection, even long after infection, often recurs after LASIK and affects refraction and visual acuity. Topical corticosteroid may be effective to prevent recurrence. Dry eye is a common complication after LASIK. Although post-LASIK dry eye is usually temporary, some patients complain of severe symptoms that may negatively influence their satisfaction with the outcome. For example, functional visual acuity significantly decreases after LASIK. The possible mechanisms for post-LASIK dry eye may be associated with loss of neurotrophic effect, damage of goblet cells, and altered corneal shape.