Episcleritis - A Simple Explanation

What is it?

Think of the eye like a layered cake. The white part of your eye is the sclera. Just above it is a thin, clear tissue called the episclera. When that thin layer gets inflamed (irritated and swollen), it's called episcleritis.

It looks like a red eye, but it is NOT the same as pink eye (conjunctivitis). It's generally a benign (harmless), self-limiting condition - meaning it goes away on its own.

Episcleritis - red eye with engorged episcleral vessels

Two Types

Feature	Simple Episcleritis (75%)	Nodular Episcleritis (25%)
Appearance	Redness only, no lump	Redness + a small raised nodule
Onset	Sudden, peaks in 24 hrs	Slower onset
Duration	Few days to 3 weeks	Longer course
Pain	Often mild or absent	More painful
Systemic disease link	Less common	More commonly linked

Simple episcleritis can be either sectoral (just one patch of redness) or diffuse (whole white of the eye is red).

Who Gets It?

Most common in middle-aged women
Can be bilateral (both eyes) in over half of cases
Recurs in about 60% of patients, but episodes tend to become less frequent over time
Rare in children

What Causes It?

Most often: No known cause (idiopathic) - about 60% of cases have no underlying disease
Sometimes linked to systemic conditions:
- Rheumatoid arthritis
- Crohn's disease / Inflammatory bowel disease
- Gout
- Herpes zoster (shingles)
- Lupus (SLE)
- Rosacea
Rarely: infections (syphilis, Lyme disease), medications (topiramate, pamidronate)

Symptoms

Red or pink eye (sectoral patch or the whole white)
Mild discomfort or grittiness - up to 50% feel no pain at all
Mild watering
Sometimes mild photophobia (light sensitivity)
No discharge (this helps rule out conjunctivitis)
Vision is always normal - episcleritis does NOT affect vision

How is it Diagnosed?

The key clinical test is the phenylephrine 2.5% drop test:

Put the drop in the eye, wait 10-15 minutes
In episcleritis: the red vessels blanch (go white) because the vessels are superficial
In scleritis (deeper, more serious): vessels do NOT blanch - they stay red/purple

Another clue: the engorged episcleral vessels can be gently moved with a cotton swab - they're not fixed like in scleritis.

Key Difference: Episcleritis vs. Scleritis

Feature	Episcleritis	Scleritis
Depth	Superficial (episclera)	Deep (sclera itself)
Pain	Mild or none	Severe, deep, boring pain
Colour	Bright red	Violaceous (bluish-purple) hue
Phenylephrine test	Vessels blanch	Vessels do NOT blanch
Vessels move with swab?	Yes	No
Vision affected?	No	Can be
Systemic disease link	Sometimes	Frequently
Danger level	Benign	Can be sight-threatening

Treatment

Treatment depends on severity:

Mild cases: No treatment needed - just cool compresses or refrigerated artificial tears (lubricating eye drops)
Moderate cases:
- Topical NSAIDs (e.g., diclofenac 0.1% four times a day)
- Mild topical steroids (e.g., fluorometholone 0.1% four times a day)
Severe or recurrent cases:
- Oral NSAIDs such as ibuprofen 200-600 mg three times a day for 10-14 days (take with food)
- Naproxen or flurbiprofen are alternatives
If systemic disease found: Treat the underlying cause with a rheumatologist

Prognosis

Excellent. Episcleritis is not dangerous and does not cause permanent eye damage or vision loss. Most episodes last a few days to 3 weeks. It can recur but tends to become less frequent over time.

Key memory tip: Episcleritis = superficial, benign, bright red, blanches with phenylephrine, mild pain or none, good prognosis. Scleritis = deep, potentially serious, violaceous/purple, does NOT blanch, severe pain, worse prognosis.

Sources: Kanski's Clinical Ophthalmology 10th Ed.; Wills Eye Manual

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