Dry eye and blepharitis: approaching the patient with chronic eye irritation.

Dry eye is the most common cause for chronic eye irritation in the patient over age 50 years and is multifactorial in etiology. Whatever the etiology, the final common pathway is loss of water from the tear film, with an increase in tear film osmolarity. Patients with dry eye experience sandy-gritty irritation, dryness, burning, or increased awareness of their eyes that gets worse as the day goes on. These patients need to be distinguished from patients with posterior blepharitis, or meibomitis, in which similar symptoms are worse on eye opening. Dry eye treatment includes strategies to lower tear film osmolarity and treat associated eyelid disease. The effectiveness of available treatments often leaves something to be desired. This condition may be severely disabling in advanced cases.