Definition

• Peripheral corneal thinning ± sterile infiltrate or ulcer

Differential Diagnoses

• Peripheral Ulcerative Keratitis (PUK)
  • Group of inflammatory diseases leading to peripheral corneal thinning
  • Unilateral or bilateral
  • Crescent-shaped ulceration and stromal infiltration at the limbus, epithelial defect. Circular and occasionally central spread ^{1 2 3 4}
  • Mostly limbitis, episcleritis, scleritis. Perforation can occur.
  • Often associated with dry eye
  • Systemic comorbidities must be investigated!
    • Rheumatoid arthritis (most common)
    • Granulomatosis with Polyangiitis (second most common)
    • Relapsing Polychondritis
    • Systemic lupus erythematosus
• Mooren’s Ulcer
  • Special form of PUK without scleritis, by definition idiopathic without local or systemic underlying disease, diagnosis by exclusion!
  • Unilateral or bilateral
  • Severe pain is typical
  • Peripheral stromal ulcerations with epithelial defect, central lesion with overhanging edge, usually starting nasally or temporally with circular and later central spread; infiltrations at the periphery, vascularisations.
• Terrien’s Marginal Degeneration
  • Mostly bilateral
  • Often asymptomatic
  • No epithelial defect
  • Slowly progressive thinning of the peripheral cornea, typically superior; sometimes with yellowish linear deposition (lipids), irregular astigmatism possible ^{5 6}
• Corneal Dellen
  • Localized, mostly oval corneal thinning; usually next to a raised lesion
  • Caused by drying -> lubricating drops
• Pellucid Marginal Degeneration
• Marginal keratitis
  • Rule out infectious ulcer -> bacterial keratitis / fungal keratitis
• Ocular Rosacea
• Senile Furrow Degeneration
  • decreasing width of the peripheral cornea between the arcus senilis and limbus

Work-up

• History: especially systemic (rheumatic) or ocular pre-existing conditions?
• Complete slit-lamp examination including fundoscopy (Cotton-Wool spots? Signs of posterior scleritis?)
• consider Schirmer test
• Laboratory tests: Complete blood count, CRP, ESR, RF, anti citrullinated protein antibodies (ACPA), ANA, ANCA
• corneal swab when infectious aetiology is suspected
• consider scleritis – workup