Blepharitis pathophysiology: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
The exact pathogenesis of blepharitis is unknown, but suspected to be multifactorial. | 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]]. Patients’ lipid tear layer destabilizes, causing uneven spreading of tears and increased aqueous tear evaporation. It is impossible to eliminate all bacteria with antibiotics; it’s also undesirable. Bacteria play a critical role in normal eye homeostasis. | |||
Some clinicians believe that [[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. | |||
===Staphylococcal Blepharitis=== | ===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 | 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=== | ||
Seborrheic blepharitis is characterized by less [[inflammation]] than staphylococcal blepharitis but with more oily or | 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. | ||
==Associated Conditions== | ==Associated Conditions== | ||
Blepharitis often is associated with [[systemic diseases]], such as: | |||
*[[Rosacea]] | |||
*[[Atopy]] | |||
*[[Systemic lupus erythematous|systemic lupus erythematous (SLE)]] | |||
*[[Sjögren's Syndrome]] | |||
*[[Seborrheic dermatitis]] | |||
Blepharitis also is associated with [[ocular diseases]], such as: | |||
*[[Conjunctivitis]] | |||
*[[Keratitis]] | |||
*[[Dry eye syndrome]] | |||
*[[Chalazion]] | |||
Trichiasis, | |||
==Gross Pathology== | ==Gross Pathology== | ||
On [[gross pathology]], [feature1], [feature2], and [feature3] are characteristic findings of [disease name]. | |||
==Microscopic Pathology== | ==Microscopic Pathology== | ||
On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name] | |||
==Images== | ==Images== | ||
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[[Category:Primary care]] | [[Category:Primary care]] | ||
[[Category:Ophthalmology]] | [[Category:Ophthalmology]] | ||
{{WH}} | {{WH}} | ||
{{WS}} | {{WS}} | ||
Revision as of 12:45, 12 July 2016
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Blepharitis Microchapters | |
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Diagnosis | |
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Treatment | |
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Case Studies | |
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Blepharitis pathophysiology On the Web | |
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American Roentgen Ray Society Images of Blepharitis pathophysiology | |
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Risk calculators and risk factors for Blepharitis pathophysiology | |
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. 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. Patients’ lipid tear layer destabilizes, causing uneven spreading of tears and increased aqueous tear evaporation. It is impossible to eliminate all bacteria with antibiotics; it’s also undesirable. Bacteria play a critical role in normal eye homeostasis.
Some clinicians believe that 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.
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.
Associated Conditions
Blepharitis often is associated with systemic diseases, such as:
Blepharitis also is associated with ocular diseases, such as:
Trichiasis,
Gross Pathology
On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
Microscopic Pathology
On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name]