PUK, interstitial keratitis and scleritis
Key Takeaways
Peripheral ulceration with thinning requires urgent assessment of infection, perforation and systemic inflammatory disease.
Destructive scleritis can indicate systemic vasculitis and is not managed adequately by surface lubrication alone.
Blanching and ultrasound signs support differentiation but cannot replace the complete clinical assessment.
Peripheral Ulcerative Keratitis
Peripheral ulcerative keratitis (PUK) is a crescentic inflammatory ulcer with epithelial loss and stromal thinning near the limbus. Pain, photophobia, injection and adjacent scleritis may occur, but presentation varies. The peripheral vascular/immune environment permits inflammatory-cell recruitment and collagen degradation. The immediate questions are whether infection is present, whether thinning threatens perforation and whether an associated systemic vasculitis needs urgent treatment.
Assess acuity, defect extent/depth, infiltrate, sclera, anterior chamber and leakage when safe. Avoid pressure on a very thin cornea. Obtain microbiological samples for a possible infectious ulcer without delaying antimicrobial care. Ask about rheumatoid arthritis, respiratory/renal symptoms, skin disease, inflammatory bowel disease, prior surgery, medication and systemic infection risk. Rheumatoid disease and granulomatosis with polyangiitis (GPA) are important associations, but an unreferenced percentage does not establish the diagnosis.
Immune-mediated PUK can signal serious systemic disease and needs urgent corneal and rheumatology care. Systemic corticosteroids and steroid-sparing treatment may be required once infection is excluded or appropriately covered; use targeted immune treatment rather than automatically administering it before assessment. GPA may need rituximab or cyclophosphamide-based induction according to the systemic team. Topical steroid monotherapy is inadequate for systemic vasculitic PUK and can worsen infection or melting. Local lubrication, anticollagenolytic measures and protective procedures complement treatment of the cause. Glue, amniotic membrane or tectonic grafting may be needed for impending or established perforation, with size, location and tissue viability guiding choice.
Mooren Ulcer and Interstitial Disease
Mooren ulcer is a painful progressive peripheral ulcer with an undermined edge, diagnosed after excluding infection and systemic causes. Absence of a recognised systemic disease does not make every peripheral ulcer Mooren disease. Assess both eyes, age, progression and scleral involvement; treatment ranges from local immune control to specialist systemic therapy and reconstruction.
Interstitial keratitis is inflammation primarily within the stroma, often with vascularisation and little primary epithelial ulceration. Causes include syphilis, herpes, TB-associated disease and immune disorders. Distinguish an active infectious process from immune-mediated scarring before prescribing steroids. Ghost vessels indicate prior vascularisation rather than current cause. Syphilis testing needs stage/treatment interpretation and systemic antimicrobial treatment when indicated.
Cogan syndrome classically combines non-syphilitic interstitial keratitis with audiovestibular disease. New hearing symptoms or systemic vascular signs warrant urgent medical/ENT assessment; treatment is chosen for organ threat and infection exclusion. A corneal appearance alone does not diagnose Cogan or justify one automatic high-dose regimen. Review drug toxicity, autoimmune and infectious alternatives.
Episcleritis versus Scleritis
Episcleritis usually causes local superficial injection with irritation and relatively preserved vision. Scleritis often produces deeper violaceous injection, tenderness and substantial boring pain, sometimes radiating or waking the patient. Pain can be reduced in necrotising disease without inflammation or neuropathy, so absence of severe pain is not reassuring by itself. Examine cornea, pressure, pupils and posterior segment and assess whether the globe is threatened.
| Feature | Episcleritis | Scleritis |
|---|---|---|
| Tissue | Superficial episcleral vessels | Deeper sclera with possible thinning |
| Symptoms | Often mild discomfort | Often deep pain and tenderness |
| Vision | Usually preserved | Can be affected by associated disease |
| Phenylephrine | Superficial vessels often blanch | Deep vessels may persist; this is supportive, not definitive |
| Management | Lubrication and selected anti-inflammatory care | Cause- and severity-based systemic assessment/treatment |
Phenylephrine testing is not an infallible discriminator and may be inappropriate with particular cardiovascular or ocular conditions. Consider keratitis, uveitis, angle closure and orbital disease if symptoms or findings do not fit. Recurrent episcleritis may justify systemic review guided by history; every mild first episode does not need an indiscriminate laboratory panel.
Scleritis Classification and Management
Anterior scleritis may be diffuse, nodular or necrotising. Necrotising disease threatens globe integrity and may accompany systemic vasculitis. Infectious scleritis is particularly relevant after surgery/trauma and must be distinguished from immune disease before escalating steroids. Posterior scleritis can cause pain, reduced vision, disc swelling, choroidal folds or an exudative detachment. Ultrasound may show scleral thickening and a T-sign from fluid around the optic nerve, but absence of that sign does not exclude the diagnosis.
Mild non-necrotising immune disease may respond to an oral NSAID if renal, gastrointestinal, cardiovascular and other risks permit. More severe or resistant disease may require systemic corticosteroids and immunomodulation, selected with medical specialists. Topical therapy may be an adjunct but usually does not adequately control deeper severe disease. Do not provide a high-dose indomethacin recipe or assume every posterior case needs the same IV steroid/cyclophosphamide combination.
Investigation follows the phenotype and systemic history: blood count, renal/urine assessment, inflammatory markers and targeted infection/autoimmune tests may identify an actionable cause. Monitor pain, inflammation, thinning, pressure and posterior complications and reassess the diagnosis if treatment fails. Provide urgent return advice for reduced vision, new leakage, escalating pain or systemic deterioration.
Clinical Reasoning Example
A patient with a painful peripheral crescentic defect, stromal loss and deep injection has a threatening ulcer and possible scleritis. Describe the size/depth and assess leakage without pressure, obtain infection-directed samples, and arrange urgent corneal/systemic review. A history of arthritis increases concern for immune disease but does not eliminate infection. Starting only a steroid drop would fail to address the systemic threat and could worsen microbial disease. Once the cause is assessed, combine systemic treatment with local protection and close review.
A peripheral inflammatory ulcer has thinning and adjacent scleritis. What is the immediate priority?
Prescribe topical steroid monotherapy without examination
Assume Mooren ulcer because it is peripheral
Exclude or address infection, assess perforation and arrange urgent corneal/systemic review
Wait for spontaneous healing
Which finding supports posterior scleritis but is not required in every case?
A normal pupil proving the diagnosis
A fixed retinal-drusen count
An elevated Newcastle score
A T-sign and scleral thickening on ultrasound
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