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. 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. In most blepharitis cases, the eyelids are colonized with bacteria, usually Staphylococcus epidermidis, Corynebacteria, or Staphylococcus aureus. Bacterial lipase changes meibomian gland secretions, increasing cholesterol concentration and creating an environment that promotes bacterial growth and proliferation. Bacterial toxins, mattering, and enzymes can also create inflammation.
Meibomian gland dysfunction is characterized by functional abnormalities of themeibomian 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. This can contribute to symptoms experienced in Meibomian gland dysfunction (MGD) blepharitis.
Demodex folliculorum small parasitic mites that live in hair follicles, sebaceous glands, and meibomian glands may caused or contributed to chronic blepharitis. This theory is still controversial. Demodex infestation has been implicated in rosacea, which is often accompanied by blepharitis.
Associated Conditions
Blepharitis often is associated with systemic diseases, such as:
Blepharitis also is associated with ocular diseases, such as:
Gross Pathology
On gross pathology, lid margin swelling, misdirection of lashes, madarosis,oily or greasy deposits on lid margins, crusting of anterior lid margin, lid margin hyperaemia, and conjunctival hyperaemia are characteristic findings of blepharitis.
Microscopic Pathology
On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name]