How do you differentiate between scleritis, episcleritis, and conjunctivitis on a patient's exam, considering their symptoms, medical history, and physical examination findings?

Differentiating Scleritis, Episcleritis, and Conjunctivitis on Physical Examination

The key to distinguishing these three conditions lies in pain severity, depth of vessel involvement, and presence of visual changes: conjunctivitis causes minimal pain with discharge and superficial redness; episcleritis presents with mild or no pain and superficial vessel hyperemia without visual changes; scleritis causes severe, boring pain with deep vessel injection and potential vision loss. 1, 2, 3

Pain Assessment: The Primary Discriminator

Pain intensity is your most reliable clinical differentiator:

• Conjunctivitis: Minimal to no pain; primarily irritation, itching, or foreign body sensation 1
• Episcleritis: Mild pain or relatively painless; described as burning or itching 1, 2, 3
• Scleritis: Severe, boring, deep ocular pain that often radiates to the face, jaw, or head; frequently wakes patients from sleep 1, 4, 5

Visual Acuity and Photophobia

Check visual acuity immediately—this distinguishes benign from sight-threatening conditions:

• Conjunctivitis: Vision typically normal; may have mild blurring from discharge 1
• Episcleritis: Vision always preserved; no photophobia 2, 6, 3
• Scleritis: Visual disturbance common; moderate to severe photophobia present 1, 6, 3

Any patient with visual disturbance, photophobia, or moderate-to-severe pain requires urgent ophthalmology referral for slit-lamp examination to rule out scleritis or uveitis. 1, 6, 3

Vessel Involvement and Redness Pattern

Examine the depth and pattern of vascular injection:

Conjunctivitis

• Diffuse superficial conjunctival injection (bright red) 1
• Vessels blanch with topical vasoconstrictors
• May have follicular or papillary reaction on tarsal conjunctiva 1
• Discharge present (watery, mucoid, or purulent depending on etiology) 1

Episcleritis

• Superficial episcleral vessel hyperemia (salmon-pink or bright red) 2, 3
• Sectoral or diffuse pattern 1
• Vessels mobile over underlying sclera
• No discharge 2, 3
• Hyperemic sclera and conjunctiva without deep vessel involvement 1, 6

Scleritis

• Deep scleral vessel injection (dark red or violaceous hue) 4, 5
• Vessels do NOT blanch with topical vasoconstrictors
• May have scleral edema or nodules 4, 5
• Can progress to scleral necrosis in necrotizing forms 4, 5, 7

Associated Ocular Findings

Look for these additional examination findings:

Conjunctivitis-Specific Features

• Eyelid mattering and adherence upon waking 1
• Preauricular lymphadenopathy (viral or chlamydial) 1
• Follicles on tarsal conjunctiva (viral, chlamydial) 1
• Papillae (allergic, bacterial) 1
• Subconjunctival hemorrhage possible 1

Episcleritis-Specific Features

• No corneal involvement (or minimal punctate keratitis) 2
• No anterior chamber reaction 3
• Sectoral or diffuse episcleral injection 1, 3

Scleritis-Specific Features

• Scleral edema and nodules 4, 5
• Corneal involvement common (keratitis, peripheral ulcerative keratitis) 4, 8
• Anterior chamber inflammation may be present 8
• Risk of complications: glaucoma, uveitis, retinal detachment 9, 8

Critical Pitfalls to Avoid

Do not mistake scleritis for episcleritis—this delays treatment and risks permanent vision loss. 4, 5 The presence of severe pain, deep vessel involvement, or any visual changes mandates urgent ophthalmology referral. 1, 3

Episcleritis may precede diagnosis of systemic inflammatory diseases (inflammatory bowel disease, rheumatoid arthritis). 1, 2, 3 Consider targeted systemic evaluation when clinical features suggest underlying autoimmune disease, particularly with recurrent episodes. 3

Infectious scleritis can mimic immune-mediated scleritis. 8, 7 Herpetic causes are regularly underestimated and must be excluded before initiating corticosteroids, which can propagate infection. 8, 7

Examination Algorithm

1. Assess pain severity: Minimal (conjunctivitis) vs. mild (episcleritis) vs. severe (scleritis) 1, 2, 3
2. Check visual acuity: Preserved in conjunctivitis and episcleritis; may be reduced in scleritis 2, 6, 3
3. Evaluate photophobia: Absent in conjunctivitis and episcleritis; present in scleritis 1, 6, 3
4. Examine vessel depth: Superficial (conjunctivitis, episcleritis) vs. deep (scleritis) 2, 3, 4
5. Look for discharge: Present in conjunctivitis; absent in episcleritis and scleritis 1, 2
6. Assess for systemic symptoms: Important for all three conditions but particularly episcleritis and scleritis 1, 3, 7

If diagnosis is uncertain or any red flags present (severe pain, vision changes, photophobia), refer urgently to ophthalmology for slit-lamp examination. 1, 6, 3