01OverviewDefinition, clinical context and the essential points that orientate the chapter.
The distinction concerns both the anatomical depth of inflammation and its clinical consequences. Episcleritis involves the vascular tissue superficial to the sclera, typically creating a sector of redness with mild tenderness or irritation. Visual function remains normal. Scleritis involves the sclera itself and can threaten the structural integrity of the eye. Its pain is often described as an ache deep within or around the eye, with radiation to adjacent facial areas. Ask specifically about sleep interruption and discomfort with eye movement, as patients may initially describe both conditions simply as a red patch.
Examine the whole eye rather than inferring the diagnosis from colour alone. Record acuity in each eye, inspect pupils and the cornea, and assess the distribution and apparent depth of the redness. An episcleral nodule can create focal elevation; nodular scleritis can also occur, so a visible lump does not establish a benign diagnosis. Slit-lamp assessment is especially valuable when pain is more than mild, the appearance is atypical or the examiner is uncertain. A specialist may use vascular blanching to help distinguish tissue layers, but this is not a prerequisite for referral.
Systemic context matters, particularly for recurrent episcleritis and any scleritis. Ask about inflammatory arthritis, connective-tissue disease, inflammatory bowel symptoms, respiratory or renal features of vasculitis, infections and recent eye surgery or trauma. The absence of a known systemic diagnosis does not make scleritis unlikely enough to dismiss. Investigations should be guided by the ophthalmic examination and history, because infectious and immune-mediated disease can require very different treatment. A broad untargeted panel must not delay the initial eye assessment.
Key points
- Episcleritis affects superficial tissue and usually causes mild discomfort with preserved vision; scleritis affects the deeper scleral coat.
- Episcleritis is commonly self-limiting over seven to ten days, although recurrence should prompt reconsideration of associated disease.
- Scleritic pain can be deep, radiating and severe enough to disturb sleep, but important exceptions occur.
- Scleritis may accompany systemic autoimmune disease, infection or prior ocular intervention and needs an aetiological assessment.
- Posterior scleritis may produce pain and visual symptoms without obvious anterior redness.
- Avoid empirical ocular steroids until the diagnosis and relevant infectious causes have been assessed.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Often isolated superficial disease
Many episcleritis episodes occur without an identified systemic disorder. Repeated episodes or an atypical course increase the value of reassessing systemic symptoms and the original ocular diagnosis.
Immune-mediated scleral inflammation
Scleritis can accompany rheumatoid arthritis, vasculitic disease or other systemic inflammation. Ocular involvement may occur before the associated medical disorder has been recognised or fully characterised.
Infection or local injury
Infection, trauma and previous ocular surgery can be relevant to scleral disease. These possibilities matter because immunosuppressive treatment may be inappropriate or hazardous without aetiological assessment.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Superficial vascular inflammation
Episcleral inflammation creates redness in the tissues above the sclera. Its limited depth usually preserves ocular structure and visual function during an uncomplicated self-limiting episode.
- 2Deep tissue injury
Inflammation within the scleral coat can produce substantial pain and disrupt collagenous tissue. Necrosis and thinning threaten the mechanical integrity of the globe.
- 3Posterior extension
Disease behind the visible anterior sclera can disturb adjacent ocular structures and vision without prominent surface redness. This anatomical location explains why inspection alone may be misleading.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Localised or diffuse superficial redness with mild soreness, preserved acuity and little or no photophobia supports episcleritis when the cornea and deeper eye are normal.
A deep red or violaceous hue, marked globe tenderness and severe radiating pain suggest scleral inflammation, particularly when vision or the adjacent cornea is affected.
Pain, visual disturbance or pain on eye movement can occur despite little obvious redness at the front of the eye; specialist imaging may be needed.
Scleral thinning or an abnormal dark appearance is concerning even with limited discomfort; some necrotising disease, especially with rheumatoid disease, may be relatively painless.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Visual acuity, pupils and corneal inspectionFirst step - Why
- Assess ocular function and identify associated sight-threatening findings.
- Interpretation and limitations
- Visual reduction, pupil abnormality or corneal damage argues against reassurance for uncomplicated episcleritis and supports urgent specialist assessment.
- 02
Slit-lamp assessment of inflammatory depth - Why
- Distinguish superficial episcleral changes from deeper scleral involvement.
- Interpretation and limitations
- Vessel depth, tenderness, nodularity and associated intraocular inflammation inform the diagnosis; an uncertain examination should increase rather than reduce referral urgency.
- 03
Specialist posterior-segment examination and ultrasound - Why
- Investigate suspected posterior disease or unexplained visual symptoms.
- Interpretation and limitations
- Posterior scleritis can require ocular imaging even when anterior inspection is unrevealing; imaging choice and interpretation belong within the urgent ophthalmic assessment.
- 04
Targeted systemic and infectious investigations - Why
- Identify an associated disorder and support safe treatment selection.
- Interpretation and limitations
- Blood count, inflammatory markers, renal assessment, urinalysis or directed autoimmune and infection tests depend on the history and specialist findings, not a universal screening panel.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Anterior uveitis
Pain, photophobia and redness overlap with scleritis, but anterior chamber cells, flare and pupil changes suggest intraocular inflammation. Both conditions may coexist and need specialist examination.
Microbial keratitis
An epithelial defect and corneal infiltrate indicate a corneal infectious process. Contact-lens wear, trauma or an ulcer changes the management priority despite surrounding scleral redness.
Subconjunctival haemorrhage
A sharply demarcated patch of blood can appear dramatic but is usually painless with normal vision. Deep pain or visual change makes an uncomplicated haemorrhage explanation inadequate.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Superficial inflammationRelieve symptoms and explain the expected courseFirst stepAssessment supports uncomplicated episcleritis with normal vision and no concerning corneal or intraocular findings.+
- 1Explain that symptoms commonly resolve within seven to ten days and offer cold compresses or artificial tears for comfort.
- 2Discuss whether clinical review is needed for troublesome discomfort, avoiding unexamined steroid treatment or assumptions about oral NSAID suitability.
- 3Provide clear instructions to return earlier for increasing pain, photophobia or visual change rather than waiting for spontaneous resolution.
02Deeper inflammationArrange emergency ophthalmology and a cause-directed planThe history or examination raises concern for anterior, posterior or necrotising scleritis.+
- 1Contact the emergency ophthalmic service and communicate pain severity, visual acuity, systemic illness and any scleral or corneal thinning.
- 2Let the specialist establish the extent and likely cause before systemic anti-inflammatory or immunosuppressive treatment is selected.
- 3Coordinate rheumatology, medical or infection input when indicated, while maintaining ophthalmic monitoring for structural damage and treatment response.
03Recurrent episodesReview the diagnosis and systemic contextEpiscleritis recurs repeatedly, persists beyond its usual course or develops atypical features.+
- 1Recheck that each episode truly has preserved vision, mild discomfort and no evidence of deeper scleral or corneal involvement.
- 2Consider ophthalmology assessment and systemic investigation after the second recurrence, with earlier referral when symptoms or medical history are concerning.
- 3Document associated joint, bowel, skin, respiratory and urinary symptoms and arrange focused follow-up rather than repeated isolated symptom treatment.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
Carmellose sodium for comfort in uncomplicated episcleritis
One to two drops into the affected eye as needed, using a suitable 0.5% or 1% formulation and the manufacturer's opening-expiry instructions.Use only alongside appropriate diagnostic assessment. Increasing pain or altered vision requires reassessment, not escalating lubricant use. Leave at least five minutes between different ocular drops.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Scleral thinning and perforation
Destructive scleral inflammation can weaken the globe and expose deeper pigmented tissue. A dark or thinned area requires urgent specialist assessment even when pain is limited.
Adjacent ocular inflammation
Scleritis can involve the cornea, uvea or other neighbouring structures. These complications can reduce vision and change the treatment and monitoring required.
Systemic disease consequences
An associated vasculitic or autoimmune disorder may affect organs beyond the eye. Recognising ocular inflammation can therefore trigger an important broader medical assessment.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Record the initial acuity and distribution of redness so that a later change can be interpreted against a clear baseline.
- Review an episode that fails to follow the expected improving course, especially if the original diagnosis was made without slit-lamp assessment.
- Tell patients that worsening deep pain, new photophobia or reduced vision requires urgent contact even if redness initially appeared mild.
- In scleritis, monitor through ophthalmology for inflammation, scleral integrity, corneal disease, intraocular pressure and complications of systemic treatment.
- When recurrent disease prompts systemic investigation, ensure results and referrals are followed through rather than leaving the ocular and medical assessments disconnected.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
A blanching test is not a gatekeeper
Specialists may use a vasoconstrictor response to help localise inflamed vessels. An unavailable test or uncertain response must not postpone referral for clinically suspected scleritis.
Pain has important exceptions
Severe pain is characteristic of many scleritis presentations, but posterior disease may lack redness and some necrotising disease is relatively painless. Structural and visual findings remain decisive.
Systemic treatment reflects depth
Confirmed scleritis often needs systemic anti-inflammatory treatment or immunosuppression under specialist care. A topical comfort measure cannot be assumed to control deep scleral inflammation.
Infection changes the treatment choice
Previous surgery, trauma or infection exposure can alter the differential. Immunosuppression before an appropriate infection assessment may worsen an infectious scleral process.
11Common pitfallsFrequent interpretation and management errors.
- 01
Equating all sharply localised redness with benign episcleritis without asking about deep pain and checking vision.
- 02
Excluding scleritis because the anterior eye looks relatively normal despite pain and visual disturbance.
- 03
Waiting for autoimmune blood results before arranging emergency ophthalmic assessment for suspected scleral disease.
- 04
Repeating steroid drops for recurrent redness without a confirmed diagnosis or a plan to investigate persistent and atypical episodes.