eye disorders
Blepharitis
Etiology of Blepharitis
Blepharitis may be acute (ulcerative or nonulcerative) or chronic (meibomian gland dysfunction, seborrheic blepharitis). Acute ulcerative blepharitis is usually caused by bacterial infection (usually staphylococcal) of the eyelid margin at the origins of the eyelashes; the lash follicles and the meibomian glands are also involved. It may also be due to a virus (eg, herpes simplex, varicella zoster). Bacterial infections typically have more crusting than the viral type, which usually has more of a clear serous discharge. Acute nonulcerative blepharitis is usually caused by an allergic reaction involving the same area, eg, atopic blepharodermatitis and seasonal allergic blepharoconjunctivitis, which cause Intense itching and inflammation (usually along the edges of both eyelids); Rubbing (a response to itching that can increase conjunctival itching and exacerbate atopic dermatitis [eczema] of the eyelid); or Contact sensitivity (dermatoblepharoconjunctivitis) Chronic blepharitis is noninfectious inflammation of unknown cause. Meibomian glands in the eyelid produce lipids (meibum) that reduce tear evaporation by forming a lipid layer on top of the aqueous tear layer. In meibomian gland dysfunction, the lipid composition is abnormal, and gland ducts and orifices become inspissated with hard, waxy plugs. Many patients have Rosacea and Many patients with seborrheic blepharitis have Seborrheic Dermatitis of the face and scalp or acne rosacea. Secondary bacterial colonization often occurs on the scales that develop on the eyelid margin. Meibomian glands can become obstructed. Most patients with meibomian gland dysfunction or seborrheic blepharitis have increased tear evaporation and secondary Keratoconjunctivitis Sicca , also known as dry eye. 