Eyelashes are misdirected in a posterior direction, then they may rub against the globe, particularly the cornea, causing ocular surface damage. There are several possible causes:
Trichiasis is the common form of eyelash misdirection. It can arise from scarring of the lid margin causing misdirection of the lashes. Chronic blepharitis, herpes zoster ophthalmicus, trachoma, and basal cell carcinoma can cause this painful condition. However, trichiasis can also be idiopathic (meaning no obvious cause).
Pseudotrichiasis refers to eyelash misdirection due to entropion. The eyelash follicles are normal but the eyelid as a whole is misdirected causing the lashes to rub the cornea. Our office treats this condition by removing the offending lashes.