Trichiasis (/trɪkiˈeɪsɪs/ trik-ee-AY-sis, /trɪˈkaɪəsɪs/ tri-KEYE-ə-sis)[1] is a medical term for abnormally positioned eyelashes that grow back toward the eye, touching the cornea or conjunctiva.

Standard treatment involves removal or destruction of the affected eyelashes with electrology, specialized laser, or surgery.

Severe cases may cause scarring of the cornea and lead to vision loss if untreated.

Trichiasis in dogs is hair from the eyelid growing in the wrong direction and rubbing on the eye, causing irritation.

This type of trichiasis can be flattened by rubbing petroleum jelly onto it, but surgery is sometimes necessary for permanent correction.