What Causes Chronic Blepharitis
Chronic blepharitis has three primary causes: staphylococcal infection, seborrheic dermatitis, and meibomian gland dysfunction (MGD), with considerable overlap between these types. 1
Primary Etiologic Categories
Staphylococcal Blepharitis
The bacterial mechanisms are complex and multifactorial:
- Staphylococcus aureus is isolated more frequently from patients with clinical staphylococcal blepharitis compared to normal subjects 1
- Coagulase-negative staphylococcus is present in 89-100% of both normal and affected eyelids, but plays a pathogenic role through poorly understood mechanisms 1
- Immunologic mechanisms are key: 40% of chronic blepharitis patients show enhanced cell-mediated immunity to S. aureus (not seen in normal subjects) 1
- Staphylococcal antigens directly trigger inflammation by binding to bacterial antigen receptors on corneal epithelium 1
Important caveat: The presence of staphylococcus alone doesn't confirm causation—toxin production correlates inconsistently with disease severity 1
Seborrheic Blepharitis
- Characterized by greasy scaling of the anterior eyelid 1
- Frequently coexists with seborrheic dermatitis of eyebrows and scalp 1
- Often overlaps with other dermatologic conditions including rosacea and atopic dermatitis 1
Meibomian Gland Dysfunction (MGD)
MGD is the most common cause of evaporative dry eye disease 1:
- Altered biochemical composition of meibomian secretions leads to decreased normal meibum availability 1
- This cascade results in tear film hyperosmolarity, instability, increased bacterial growth, evaporative dry eye, and ocular surface inflammation 1
- 74% of patients with primary meibomitis have seborrheic dermatitis, and 51% have rosacea 1
Secondary Contributing Factors
Demodex Infestation
- Found in 30-68% of chronic blepharitis patients (especially older patients) 1
- Critical distinction: Also found in significant percentages of patients without blepharitis, making causation unclear 1
- However, patients with recalcitrant blepharitis respond to Demodex-directed therapy 1
- Cylindrical dandruff at eyelash base is a pathognomonic sign 1
Associated Systemic Conditions
The following dermatologic conditions share common etiologies:
- Rosacea: Present in 37-52% of patients with ocular involvement 1
- Atopic dermatitis: Highly associated in both children and adults 1
- Psoriasis: Can be associated with blepharitis 1
Dry Eye Disease
A bidirectional relationship exists:
- 50% of staphylococcal blepharitis patients have dry eye 1
- Conversely, 75% of dry eye patients have staphylococcal conjunctivitis or blepharitis 1
- Tear deficiency may reduce local lysozyme and immunoglobulin levels, altering bacterial resistance 1
Rare Causes to Consider
In treatment-resistant chronic blepharitis, consider:
- Dermatophyte infections (tinea ciliaris): Microsporum audouinii and Trichophyton verrucosum have been isolated from chronic cases 2
- Pediculosis palpebrarum (Phthirus pubis): Can cause follicular conjunctivitis 1
Clinical Pitfalls
- Don't assume single etiology: There is considerable overlap between all types—most patients have multifactorial disease 1
- Age matters for differential: Staphylococcal blepharitis patients are relatively younger (mean 42 years, 80% female), while MGD increases dramatically with age (5.3% in young military personnel vs 71.1% in elderly veterans) 1
- Recurrence is common: 52.2% of anterior blepharitis cases recur after topical antibiotic treatment, with residual findings after treatment predicting higher recurrence risk 3