What are the causes of blepharitis?

Causes of Blepharitis

Blepharitis is primarily caused by bacterial infections (particularly Staphylococcus species), Demodex mite infestations, meibomian gland dysfunction, and seborrheic dermatitis, with each cause requiring specific identification and targeted treatment. 1

Anatomical Classification and Major Causes

Blepharitis can be classified by anatomical location, which helps identify the underlying causes:

1. Anterior Blepharitis

• Staphylococcal blepharitis

  • Characterized by scaling, crusting, and erythema of the eyelid margin with collarette formation at the base of the cilia 1
  • Staphylococcus aureus is isolated with greater frequency from eyelids of patients with clinical diagnoses of staphylococcal blepharitis 1
  • Pathophysiology involves bacterial toxin production and immunologic mechanisms, including enhanced cell-mediated immunity to S. aureus 1

• Seborrheic blepharitis

  • Presents with greasy scaling of the anterior eyelid 1
  • Often coexists with seborrheic dermatitis of the eyebrows and scalp 1

• Demodex blepharitis

  • Caused by Demodex mite infestation (responsible for more than two-thirds of all blepharitis cases in the US) 2
  • Two distinct species: D. folliculorum (causes anterior blepharitis) and D. brevis (causes posterior blepharitis) 3
  • Pathognomonic sign: collarettes (waste products of Demodex mites) at the base of eyelashes 2
  • Risk factors include increasing age, rosacea, and diabetes 4

2. Posterior Blepharitis

• Meibomian gland dysfunction (MGD)
  • Characterized by terminal duct obstruction and/or qualitative/quantitative changes in glandular secretion 1
  • Clinical signs include prominent blood vessels crossing the mucocutaneous junction, frothy discharge, pouting or plugging of meibomian orifices, and altered meibomian secretions 1
  • Can lead to eventual atrophy and fibrosis of the meibomian glands 1
  • Often coexists with rosacea or seborrheic dermatitis 1

Pathophysiological Mechanisms

Bacterial Mechanisms

• Staphylococcal antigens can directly initiate inflammatory reactions by attaching to bacterial antigen-binding receptors on the corneal epithelium 1
• Toxin production may correlate with blepharoconjunctivitis, though evidence is mixed 1
• Cell-mediated immunologic mechanisms are implicated in the development of keratitis associated with staphylococcal blepharitis 1

Demodex Mechanisms

• Direct mechanical damage to eyelid tissues 4
• Serving as a vector for bacteria 4
• Inducing hypersensitivity and inflammation 4
• Can cause blockage and atrophy of meibomian glands, worsening dry eye disease 2

Meibomian Gland Dysfunction Mechanisms

• Alterations in biochemical composition of meibomian gland secretions 1
• Decreased availability of normal meibum to the lid margin and tear film 1
• Results in hyperosmolarity and instability of the tear film 1
• Promotes increased bacterial growth on the lid margin 1
• Leads to evaporative dry eye and ocular surface inflammation 1

Less Common Causes

• Carcinoma or immune-mediated diseases should be considered in non-responsive blepharitis, particularly if associated with loss of eyelashes and/or conjunctival cicatricial changes 1

• Medication side effects can cause eyelash abnormalities that may mimic or contribute to blepharitis 5

  • Prostaglandin analogs (bimatoprost, latanoprost) used for glaucoma can affect eyelash growth and appearance 5

• Endocrine disorders may contribute to eyelash abnormalities and should be excluded in the diagnosis 5

Clinical Implications

Proper identification of the specific cause of blepharitis is crucial as it guides appropriate treatment. For example:

• Staphylococcal blepharitis may require antibiotics 6
• Demodex blepharitis responds to specific treatments like tea tree oil or lotilaner ophthalmic solution 4, 3
• MGD benefits from warm compresses and thermal pulsation treatments 7

Early diagnosis and appropriate treatment of the underlying cause can prevent complications including corneal involvement, vision loss, and in rare cases, disfigurement 1.