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Staphylococcal Hypersensitivity

ROUTINE — Conjunctiva

Symptoms

  • mild photophobia and discomfort: usually less severe than infectious ulcers
  • localized redness: often sectoral, matching the location of the infiltrate
  • lid crusting: "morning mattering" and greasy debris on the lashes
  • foreign body sensation: a gritty feeling exacerbated by lid movement
  • recurrence: history of multiple "styes" (chalazia) or similar red-eye episodes

Clinical Findings

Marginal infiltrates

  • "lucid interval": a clear, uninflamed strip of cornea separates the infiltrate from the limbus (diagnostic hallmark)
  • 2, 4, 8, 10 o’clock: infiltrates occur where the eyelid margins rest on the cornea
  • appearance: small (0.5–2.0 mm) white-gray subepithelial stromal opacities
  • staining: may show overlying punctate staining or a small epithelial defect

Eyelid disease (mandatory)

  • blepharitis: lash-base collarettes (crusts) and telangiectatic lid margins
  • mgd: "pouting" or capped meibomian glands with thickened, toothpaste-like secretions
  • rosacea: look for facial flushing, telangiectasias on the nose/cheeks, or rhinophyma

Phlyctenulosis

  • a raised, vascularized nodule at the limbus that "walks" toward the central cornea

Etiology

Pathophysiology

  • type iii & iv hypersensitivity: it is a sterile immune reaction, NOT an active infection
  • mechanism: staphylococcal antigens from the lid diffuse into the peripheral cornea
  • the reaction: antigens meet antibodies from limbal vessels, forming immune complexes
  • result: recruitment of inflammatory cells (PMNs) into the corneal stroma

Red Flags

  • infiltrate abutting the limbus: lack of a "lucid interval" suggests infectious keratitis
  • hypopyon or severe ac reaction: sterile infiltrates should not have pus in the chamber
  • madarosis (loss of lashes): may indicate a more serious lid malignancy (sebaceous cell)
  • phlyctenules in children: can be a rare sign of systemic Tuberculosis—rule out TB

Investigations

Clinical examination

  • slit lamp: carefully document the distance between the infiltrate and the limbus
  • lid eversion: check for meibomian gland health and presence of chalazia

Cultures

  • only indicated if the diagnosis is ambiguous or the lesion is atypical (e.g., central or touching the limbus)

Treatment

Topical management

  • steroid: low-potency (e.g., fluorometholone or loteprednol) to quiet the immune response
  • antibiotic: prophylactic cover (e.g., erythromycin ointment) to reduce bacterial load on the lids

Systemic (for rosacea/MGD)

  • doxycycline: 50–100 mg bid; acts by inhibiting bacterial lipases and reducing inflammation
  • note: children < 8 years old should use oral erythromycin instead of tetracyclines

Maintenance

  • lifelong lid hygiene is required to prevent "the rule of recurrence"

Clinical Pearl

Marginal infiltrates with a clear zone from the limbus are sterile immune responses to staph exotoxins — treat the lid margin, not just the cornea.

Differential Diagnosis

  • • infectious marginal keratitis (no lucid interval, more pain, touches the limbus)
  • • cat-scratch disease or other granulomatous conjunctivitis
  • • peripheral ulcerative keratitis (puk) associated with RA or GPA

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