Red eyes are a common presentation in patients, but its causes and consequences can vary significantly. Amongst the many differential diagnoses, episcleritis and scleritis stand out as two conditions that can look similar but have very different implications and treatments. As a medical student or a resident doctor, distinguishing between the two conditions is essential to not only triage patients, but also to prevent sight-threatening complications.
Understanding the Basics
The table below provides the basics of episcleritis and scleritis, and their differences (1).
| Feature | Episcleritis | Scleritis |
| Definition | Inflammation of the episclera, the thin layer between conjunctiva and sclera | Inflammation of the sclera, the dense fibrous outer layer of the eye |
| Onset | Acute, often recurrent | Gradual, severe |
| Pain | Mild or absent, grittiness | Severe, boring pain often radiating to the face or worse on eye movement |
| Redness | Localised, sectional, bright red | Diffuse or deep, nodular |
| Discharge | Mild watering | None |
| Visual acuity | Usually normal | Can be reduced |
| Response to Phenylephrine | Vessels will blanch | No blanching |
https://eyewiki.org/Episcleritis An image illustrating Episcleritis – Accessed 02/06/25
https://eyewiki.org/File:Recurrent_scleritis.jpg An image illustrating scleritis with an area of scleral thinning – Accessed 15/05/25
Why It Matters
Episcleritis is typically benign, self-limiting, and idiopathic. It can be associated with mild systemic disease like rosacea or mild autoimmune conditions (2). The condition tends to resolve within two weeks and may not require more than lubricants, NSAIDs or a short course of weak topical steroids such as loteprednol or fluorometholone.
In contrast, scleritis is a serious inflammatory disorder often linked to systemic autoimmune conditions such as rheumatoid arthritis, granulomatosis with polyangiitis, or lupus (3). If untreated, it can lead to complications like scleral thinning or associated uveitis, that can lead to vision loss. Scleritis will likely require a course of systemic treatment with NSAIDs such as Flurbiprofen or oral prednisolone, with the need for systemic immunosuppression in severe or recurrent cases (4).
Red Flags Pointing Toward Scleritis
- Pain which wakes the patient up at night (high on pain grade scale)
- Pain with eye movement or palpation
- Reduced visual acuity
- Violaceous hue of scleral vessels, areas of scleral translucency
- Systemic autoimmune symptoms (e.g., joint pain, rash)
What You Can Do as a Resident
Even without access to a slit lamp or specialist Ophthalmic tools, there are several important steps you can take (5,6):
- History:
- Ask about the onset and severity of symptoms. Assess for systemic symptoms
- Ask about previous episodes or autoimmune diagnoses
- Visual Acuity:
- Always measure and document acuity
- External exam: In a bright room, ask the patient to look in the 4 directions of gaze, raising the eyelids when necessary, to assess the extent of the redness (diffuse or sectorial), if a nodular elevation is present or if there are any areas of scleral translucency, as well as if there’s any worsening of the pain when moving the eyes.
- Phenylephrine 2.5% Test:
- Blanching of vessels suggests episcleritis
- No blanching suggests possible scleritis
- Refer Urgently If:
- The vision is impaired
- The pain is severe
- You suspect an underlying systemic disease
Take-Home Points
- Episcleritis is a benign, mild, often self-limiting condition
- Scleritis in contrast is potentially blinding, often systemic, with significant pain that requires treatment
- Pain severity and vessel blanching are your best bedside clues
- When in doubt, refer to ophthalmology – particularly for any deep pain or visual disturbance.
References:
- Kirkwood, Bradley & Kirkwood, Rodney. (2010). Episcleritis and scleritis. Insight (American Society of Ophthalmic Registered Nurses). 35. 5-8.
- Geng RSQ, Slomovic J, Bourkas AN, Slomovic A, Sibbald RG. Ocular rosacea: the often-overlooked component of rosacea. JEADV Clin Pract. 2024; 3: 1349–1363. https://doi.org/10.1002/jvc2.428
- Parthopratim Dutta Majumder, Rupesh Agrawal, Peter McCluskey, Jyotirmay Biswas, Current Approach for the Diagnosis and Management of Noninfective Scleritis, Asia-Pacific Journal of Ophthalmology, Volume 10, Issue 2, 2021, Pages 212-223, ISSN 2162-0989,https://doi.org/10.1097/APO.0000000000000341. (https://www.sciencedirect.com/science/article/pii/S216209892300126)
- Abdel-Aty A, Gupta A, Del Priore L, Kombo N. Management of noninfectious scleritis. Ther Adv Ophthalmol. 2022 Jan 21;14:25158414211070879. doi: 10.1177/25158414211070879. PMID: 35083421; PMCID: PMC8785299.
- Salama A, Elsheikh A, Alweis R. Is this a worrisome red eye? Episcleritis in the primary care setting. J Community Hosp Intern Med Perspect. 2018 Feb 6;8(1):46-48. doi: 10.1080/20009666.2017.1418110. PMID: 29441167; PMCID: PMC5804772.
- Lagina A, Ramphul K. Scleritis. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499944/
Written by Dr Michael Milad, FY1 at West Hertfordshire NHS Trust & Reviewed by Miss Marcela Bohn, Medical Retina and Uveitis Consultant
1 thought on “Episcleritis vs Scleritis: How to Tell and Why It Matters”
This was a very insightful explanation and breakdown of the differences in the presentation of episcleritis and scleritis.