What is the difference between blepharitis and conjunctivitis in a patient with a history of chronic blepharitis?

Blepharitis vs Conjunctivitis: Key Distinguishing Features

Blepharitis is a chronic inflammatory condition primarily affecting the eyelid margins with symptoms worsening in the morning, while conjunctivitis is an acute inflammatory condition of the conjunctival membrane presenting with "red eye" and typically lacking the characteristic eyelid margin findings of blepharitis. 1, 2

Anatomic Location: The Primary Distinguishing Feature

Blepharitis targets the eyelid margin structures, including the eyelid skin, base of eyelashes, eyelash follicles (anterior blepharitis), and meibomian glands (posterior blepharitis). 1 The inflammation is centered at the lid margin with specific findings like collarette formation at the base of cilia, scaling, crusting, and vascularization crossing the mucocutaneous junction. 1

Conjunctivitis affects the conjunctival membrane that lines the eyelids and covers the exposed sclera, without primary involvement of the eyelid margin structures. 2

Clinical Presentation Differences

Blepharitis Characteristics:

• Chronic course (weeks to months) with symptoms typically worsening in the morning 1, 3
• Bilateral presentation (though can be asymmetric) 3
• Foamy discharge along the eyelid margin, not purulent 1, 3
• Collarette formation at the base of eyelashes (pathognomonic for staphylococcal type) 1, 3
• Greasy scaling on anterior eyelid in seborrheic type 1
• Meibomian gland abnormalities including pouting, plugging of orifices, and abnormal secretions ranging from turbid fluid to thick cheese-like material 1
• No fever or systemic symptoms 3
• Normal extraocular movements and vision unless corneal complications develop 3

Conjunctivitis Characteristics:

• Acute onset in most bacterial and viral cases 2
• Purulent discharge in bacterial conjunctivitis, particularly severe and bilateral in Neisseria infections 2
• Severe itching with allergen exposure in allergic conjunctivitis 2
• Conjunctival hyperemia as the primary finding without eyelid margin pathology 2
• Self-limited course in most bacterial cases (except Chlamydia and Neisseria) 2

The Critical Overlap: Blepharoconjunctivitis

Blepharitis frequently leads to secondary conjunctivitis, creating an overlap condition called blepharoconjunctivitis. 1 This occurs because chronic eyelid margin inflammation causes ocular surface inflammation, functional tear deficiency, and keratitis. 1 In patients with chronic blepharitis, the conjunctival involvement is a consequence of the primary eyelid disease rather than a separate entity. 1

Chronic conjunctivitis is usually associated with underlying blepharitis, recurrent styes, or meibomianitis, requiring treatment of the eyelid condition. 2

Diagnostic Approach in Patients with Chronic Blepharitis

Key Examination Findings for Blepharitis:

• Slit-lamp examination revealing eyelid margin vascularization, hyperemia, scaling, and crusting specifically at the lid margin 3
• Meibomian gland assessment by applying pressure to lower eyelids to evaluate expressibility and character of secretions 1
• Tear film evaluation showing foamy discharge, decreased tear meniscus, and shortened break-up time 1
• Corneal examination may show punctate epithelial erosions, marginal infiltrates, or peripheral defects as complications 1

Red Flags Requiring Immediate Action:

• Unilateral presentation with ulceration and focal lash loss should prompt immediate biopsy to rule out sebaceous carcinoma 1, 3
• Conjunctival cicatricial changes necessitate workup for ocular mucous membrane pemphigoid with immunofluorescence studies 1, 3
• Marked asymmetry and resistance to standard therapy requires biopsy to exclude malignancy 1, 3

Management Implications

For blepharitis, treatment focuses on long-term eyelid hygiene with warm compresses and lid scrubs, topical antibiotics for anterior blepharitis, and patient education about the chronic nature requiring ongoing compliance. 3, 4 Re-evaluation should occur in 2-4 weeks. 3

For conjunctivitis, treatment depends on etiology: most bacterial cases are self-limited, while Chlamydia and Neisseria require aggressive antibiotic therapy, and allergic conjunctivitis responds to topical antihistamines or mast-cell stabilizers. 2

Common Pitfall to Avoid

Do not mistake secondary conjunctivitis from chronic blepharitis for primary infectious conjunctivitis. In patients with known chronic blepharitis presenting with conjunctival hyperemia, the underlying eyelid disease is likely the culprit and should be the primary treatment target. 1, 2 Treating only the conjunctival inflammation without addressing the eyelid margin pathology will result in persistent or recurrent symptoms. 2