Written by Dr. Jia Hui Lee, MBBS (Hons) and A/Prof Elaine Chong, MBBS MEpi PhD Melb, FAMS, FRANZCO.
Episcleritis refers to inflammation of the episclera, which is a very thin layer of clear tissue that sits between the white part of the eye (the sclera, located beneath it) and another clear layer of tissue (the conjunctiva, located above it). Episcleritis causes the eye to look red, and can look very similar to another more commonly known condition called conjunctivitis or ‘pink eye’. However, unlike conjunctivitis, episcleritis is not associated with eye discharge and most cases of episcleritis have no apparent cause. In addition, episcleritis usually clears on its own without any treatment.
Figure 1. Illustration showing parts of the eye containing cornea, conjunctiva, episclera and sclera
(Source: Health Library, Tan Tock Seng Hospital, 2022)
The following sections will briefly outline how common is episcleritis, what causes episcleritis, its signs and symptoms, and some insights into its treatment.
Episcleritis is relatively uncommon. Based on populations in the United States (U.S.) and Australia, studies have estimated that episcleritis affects around 4 to 41 per 100 000 people every year , .
Episcleritis typically occurs in young to middle aged adults, and appears to affect females more commonly than males. Most cases of episcleritis have no obvious cause.
About one third of people with episcleritis may have an associated systemic inflammatory condition, such as rheumatoid arthritis, lupus or inflammatory bowel disease. Rarely, episcleritis can also be associated with certain infections, such as Lyme disease, cat-scratch disease or syphilis .
Episcleritis most commonly affects one eye, but in about one third of patients it can occur in both eyes at the same time .
There are two main types of episcleritis , :
There are 2 subtypes of episcleritis, diffuse and sectoral.
Figure 2. Diffuse episcleritis
(Source: Somepomed, 2011)
Nodular episcleritis refers to when a nodule develops in the episclera.
Figure 3. Nodular episcleritis (Source: University of Iowa Health Care, 2008)
The onset of episcleritis usually occurs quickly and suddenly. Patients with episcleritis often complain of the following:
Unlike other conditions that can also cause a red eye, episcleritis usually does not cause:
If you experience any of these signs and symptoms, schedule an appointment with an eye health professional to get your eyes checked. It is also important to note that the development of eye conditions may even start before symptoms appear, which makes going for regular and timely eye checks that much more essential.
Episcleritis is usually diagnosed by an eye care professional based on a comprehensive eye check. This includes a vision test, and a slit lamp examination (a microscope used to look at eye structures under high magnification in detail).
In episcleritis, a slit lamp examination should reveal superficial inflamed blood vessels. This helps differentiate it from other conditions such as scleritis, where the inflammation of blood vessels is deeper and appears a darker red.
If a slit lamp examination is not confirmatory, an eye drop called phenylephrine can be used to help further distinguish episcleritis from scleritis. In episcleritis, the phenylephrine eye drop will result in blanching of the superficial inflamed blood vessels, resulting in the eye looking less red 10 to 15 minutes after instillation of the eye drop. In contrast, in scleritis, the deeper inflamed blood vessels do not blanch even after instillation of the phenylephrine eye drop, and the eye will still appear to be significantly red , .
Most people who develop episcleritis do not require any further tests. However, some people may experience multiple recurrent episodes of episcleritis. In these cases, further blood tests and imaging tests, such as a chest x-ray, may be considered to look for an underlying systemic inflammatory condition or infection , .
Most cases of episcleritis are mild, and will clear on its own without any specific treatment within days to weeks. Lubricant eye drops and cool compresses can be used for symptom relief whilst allowing the condition to resolve by itself.
In some cases, if patients are especially bothered by the discomfort, eye care professionals may also prescribe non-steroidal anti-inflammatory drugs (NSAIDs) in eye drop or tablet form, or a mild steroid eye drop for a short period of time. Prolonged use of these medications may be associated with long term complications and thus their use should be kept to a minimum and only at the direction of an eye health professional .
If the episcleritis is associated with an underlying systemic inflammatory condition or infection, then treatment of the underlying condition should be undertaken.
Episcleritis usually has a good prognosis as it resolves by itself completely over 2 to 3 weeks. It is not usually associated with any long-term complications and does not cause any problems with vision.
In some cases when it is associated with an underlying systemic condition, episcleritis can be recurrent and can be associated with inflammation in other parts of the eye. In these cases, the underlying condition should be treated.
As most cases of episcleritis have no apparent cause, there is no obvious way to prevent episcleritis from occurring.
In people who have an underlying systemic inflammatory condition, episodes of episcleritis may be prevented with optimal treatment and control of their underlying condition. This should be done in conjunction with their general practitioner, medical physician or rheumatologist.
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 G. Honik, I. G. Wong, and D. C. Gritz, “Incidence and prevalence of episcleritis and scleritis in Northern California,” Cornea, vol. 32, no. 12, pp. 1562–6, 2013, doi: 10.1097/ICO.0b013e3182a407c3.
 L. P. Thong, S. L. Rogers, C. T. Hart, A. J. Hall, and L. L. Lim, “Epidemiology of episcleritis and scleritis in urban Australia,” Clinical & Experimental Ophthalmology, vol. 48, no. 6, pp. 757–766, May 2020, doi: 10.1111/ceo.13761.
 S. Schonberg and T. J. Stokkermans, “Episcleritis,” PubMed, 2022. https://www.ncbi.nlm.nih.gov/books/NBK534796/#article-21252.s2.
 American Academy Of Ophthalmology, Basic and clinical science course 2005-2006 : section 8 external disease and cornea. San Francisco, Ca: American Academy of Ophthalmology, 2005.
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