Blepharitis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mehrsefat, M.D. [2]
Overview
Blepharitis is caused by an overgrowth of the bacteria that is normally found on the skin. It is usually due to seborrheic dermatitis or a bacterial infection. Both may occur at the same time.
The cause is overgrowth of the bacteria that is normally found on the skin.
Allergies and lice that affects the eyelashes may also cause blepharitis, although these causes are less common.
People who have blepharitis have too much oil being produced by the glands near the eyelid. This allows bacteria normally found on the skin to overgrow.
Pathophysiology
The exact pathogenesis of blepharitis is unknown, but suspected to be multifactorial.
Staphylococcal Blepharitis
Staphylococcal blepharitis is believed to be associated with staphylococcal bacteria on the ocular surface. In one study of ocular flora, 46% to 51% of those diagnosed with staphylococcal blepharitis had cultures positive for Staphylococcus aureus as compared to 8% of normal patients. The mechanism by which the bacteria cause symptoms of blepharitis is not fully understood, and may include direct irritation from bacterial toxins or enhanced cell-mediated immunity to S. aureus.
Seborrheic Blepharitis
Seborrheic blepharitis is characterized by less inflammation than staphylococcal blepharitis but with more oily or greasy scaling. Some patients with seborrheic blepharitis also exhibit characteristics of Meibomian gland dysfunction (MGD). Meibomian gland dysfunction is characterized by functional abnormalities of the meibomian glands and altered secretion of meibum, which plays an important role in slowing the evaporation of tear film and smoothing the tear film to provide an even optical surface. Both quantitative deficiencies in meibum or qualitative differences in its composition can contribute to symptoms experienced in MGD blepharitis.