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Scleritis and episcleritis describe inflammation of the sclera of the eye.

 

The sclera is made up of three layers; the superficial episcleral layer, deeper scleral layer and innermost lamina fusca layer. Scleritis involves full-thickness inflammation of both the scleral and episcleral layers, and hence is a more severe ocular condition. It is common in middle-aged women, and is associated with autoimmune and systemic diseases, particularly rheumatoid arthritis. Episcleritis, however, is a benign condition limited to the episclera tissue only. It is most commonly seen in young to middle-aged females, and doesn’t typically present with sight-threatening sequela in contrast to scleritis.

 

Scleritis may be divided into two main forms; anterior and posterior scleritis. Scleral inflammation relative to the location of the extraocular recti muscle insertion determines these subtypes (either anteriorly or posteriorly). Anterior scleritis constitutes the most common form, and is further classified into diffuse (most common and treatable), nodular (presents with tender nodules) and necrotising (most severe and destructive form, with ocular complications occurring in 60% of patients) subtypes. Posterior scleritis is rarer, and associated with retinal detachment acute angle closure glaucoma and vision loss.

 

Episcleritis is largely categorised into two further subtypes; diffuse (80%) or nodular (20%). Nodular may be associated with an underlying systemic autoimmune disease.

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Diffuse anterior scleritis with small area of necrotising scleritis

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Anatomy and physiology

As a whole, the sclera is formed from strong collagen fibres, which give the eye its white colour and provide the sclera with strength. The superficial episcleral is a thin, densely vascularised layer of loose connective tissue which overlies the sclera. The scleral layer is deep to this, and forms a dense white tissue which gives the ‘white’ appearance of the bulk of the eye.

 

The exact pathophysiology of scleritis is still largely unknown, however different theories have been put forward; the association of scleritis with autoimmunity has generally been accepted, and it is considered to be a chronic inflammatory response. Inflammation begins in one area and spreads circumferentially until the entire anterior segment is involved. Scleral oedema also occurs, and collectively these processes lead to redness and swelling of the eye.

 

The pathogenesis underpinning episcleritis is a non-granulomatous inflammation of the episcleral vascular network. It’s an acute inflammatory process which similarly involves immune cell activation, including lymphocytes and macrophages. Subsequent release of inflammatory mediators causes vasodilation, increased vascular permeability and the migration of white blood cells.

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Scleritis (notice how the white Sceral layer has thinned revealing the darker purple Choroid beneath it)

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Diagnosis

 

Scleritis is typically characterised by:

• Severe ocular pain/tenderness which possibly radiates to face/cheek/jaw

• Pain which is worse upon eye movement

• Blurred vision/vision loss

• Photophobia

• History of autoimmune/systemic disease

  • e.g. rheumatoid arthritis, inflammatory bowel disease, vasculitides, systemic lupus erythematosus

• History of herpes zoster ophthalmicus

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Episcleritis is typically characterised by:

• Mild ocular discomfort/irritation

• Patchy redness of eye

• Watering of eye

• No visual changes

 

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Episcleritis

 

Examination findings include

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Scleritis

• Violet-blue hue to sclera with scleral oedema and dilatation

• Criss-crossed pattern of fixed scleral vessels

• Vessels do not blanch with phenylephrine 2.5% drops

• Slit lamp: nodules, scleral thinning, corneal infiltrates/thinning

• Systemic (non-ocular) signs: joint pain and inflammation, rashes etc

 

Episcleritis

• Red hue to sclera

• Mobile vessels - easily moved with cotton swab when gentle pressure applied to sclera

• Vessels blanch with phenylephrine 2.5% drops

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Further investigations to aid diagnosis

 

Scleritis

• Complete physical examination with attention to joints

• Laboratory tests to rule out autoimmune inflammatory disease e.g. a rheumatoid screen (FBC, ESR/CRP, RF, ANNA, a-CCP, HLA-B27, ANCA), chest X-ray, urinalysis; if any specific systemic disease is suspected, then the necessary investigations to rule these out should be performed e.g. TB, syphilis, Lyme disease

• Posterior scleritis: B-scan ultrasonography (scleral and choroidal thickening, scleral nodules, distended optic nerve sheath, fluid in Tenons capsule) and orbital MRI

 

Episcleritis

• Phenylephrine 2.5% drops: superficial episcleral vessels blanch with application, compared to scleritis where vessels do not blanch

• Rheumatoid screen only if recurrent episodes

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A - Episcleritis with a pink hue.

B - Same eye with blanching of episcleral vessels after application of phenylephrine

 

Treatment

 

The primary aim for scleritis treatment is to reduce inflammation and thus minimise damage to ocular structures. Medical therapy typically comprises oral NSAIDs as first-line, and then corticosteroids. If these still don’t adequately control the disease, immunomodulatory agents may be considered, with input from a rheumatologist. If disease is extensive and causes scleral perforation or excessive scleral thinning with a high risk of rupture, surgical intervention may be considered. Follow-up would be required to adjust medication doses dependent on the level of clinical response. Laboratory tests may be ordered to monitor systemic toxicity or to determine efficacy of treatment

 

Scleritis management is typically supportive (cool compresses, iced artificial tears) as the disease largely self-resolves within 2-3 weeks. Simple medical therapy may be used for patients experiencing pain, such as oral NSAIDs and in more severe cases, weak topical steroids may be administered. Follow-up is generally not required, however patients on topical steroids should be monitored.