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Corneal Dystrophies

CHRONIC — Cornea

Symptoms

Clinical triad

  • Bilateral, symmetric, and slowly progressive (distinguishes from degeneration or keratitis).

Visual symptoms

  • Painless, progressive vision loss (chief complaint in stromal and endothelial types).
  • Glare and haloes around lights due to light scatter from opacities or edema.
  • Morning blurred vision that clears throughout the day (classic for Fuchs endothelial dystrophy).

Recurrent erosions

  • Episodes of acute pain, photophobia, and tearing upon waking (common in EBMD, Meesmann, Reis–Bücklers, lattice, and granular).

Onset windows

  • Congenital: CHED.
  • 1st Decade: Macular.
  • 1st–2nd Decade: Lattice, Granular.
  • 3rd–4th Decade: EBMD.
  • 5th–7th Decade: Fuchs.

Clinical Findings

Epithelial layer

  • EBMD (Map–Dot–Fingerprint): subtle patterns in basal epithelium; highlighted with retroillumination or by drying the cornea.
  • Meesmann: fine intraepithelial cysts across the entire cornea; best seen on retroillumination.
  • Reis–Bücklers: reticular gray-white subepithelial opacities at the level of Bowman layer; painful recurrent erosions.

Stromal layer

  • Granular (TGFBI): discrete white "crumb-like" opacities in central anterior stroma; spares the limbus (Hyaline/Masson trichrome).
  • Lattice (TGFBI): branching refractile linear deposits (Amyloid/Congo red).
  • Macular (CHST6): diffuse cloudy stroma with poorly-defined opacities extending to the limbus; most visually devastating (Mucopolysaccharide/Alcian blue).
  • Schnyder: central crystalline deposits and stromal lipid; associated with systemic hyperlipidemia.

Endothelial layer

  • Fuchs: central endothelial guttae ("beaten-metal" appearance on specular reflection); progresses to stromal edema and bullae.
  • Posterior Polymorphous (PPMD): bands, vesicles, or geographic patterns at the endothelium.
  • Congenital Hereditary Endothelial Dystrophy (CHED): ground-glass corneal clouding present at birth.

Unifying negative findings

  • NO conjunctival injection, NO vascularization, and NO active infiltrate (presence suggests keratitis or scarring).

Etiology

Genetics

  • Autosomal Dominant (most common): EBMD, Granular, Lattice, Fuchs, PPMD, Reis–Bücklers.
  • Autosomal Recessive: Macular dystrophy, CHED.

Specific genes

  • TGFBI (5q31): Granular, Lattice, Reis–Bücklers.
  • CHST6: Macular (keratan sulfate synthesis defect).
  • COL8A2 / TCF4: Fuchs.

Red Flags

Bilateral edema in an infant → consider CHED vs congenital glaucoma; requires urgent pediatric referral.

Progressive central clouding in children → high risk for amblyopia; requires aggressive management.

Middle-aged Fuchs patient with rapid visual decline → impending corneal decompensation.

Recurrent erosion with hypopyon or worsening pain → suspect superimposed microbial keratitis.

Investigations

Clinical tools

  • Slit lamp exam: identify lesion depth (epithelial vs stromal vs endothelial).
  • Retroillumination: highlights EBMD, Meesmann, and guttae.
  • Pachymetry: maps corneal thickness; >640 μm suggests significant edema.

Specialized imaging

  • Specular microscopy: quantifies endothelial cell density (normal >2000 cells/mm²).
  • Anterior Segment OCT / Pentacam: maps opacity depth to guide PTK treatment.

Systemic & genetic

  • Fasting lipid panel: mandatory for Schnyder dystrophy.
  • Genetic testing: for diagnosis confirmation or family planning.

Treatment

Recurrent erosion ladder

  • Lubrication: PF artificial tears and ointment qhs.
  • Hypertonic saline: 5% NaCl (Muro 128) qid + ointment qhs.
  • Procedural: Bandage contact lens (6–8 weeks) → epithelial debridement/micropuncture → excimer PTK.

Endothelial management (Fuchs)

  • Mild edema: topical hypertonic saline.
  • Visually significant edema: DMEK (Descemet membrane endothelial keratoplasty) or DSAEK.
  • Triple procedure: combined Phaco/IOL and DMEK for borderline cell counts.

Stromal & congenital management

  • Anterior stromal opacities: excimer PTK.
  • Deep/diffuse disease: DALK (deep anterior lamellar keratoplasty) or PK.
  • Macular dystrophy: typically requires PK due to full-thickness limbus-to-limbus involvement.
  • CHED: PK in infancy to prevent amblyopia.

Clinical Pearl

Remember "MARILYN MONROE Always Gained Her Men's Lovers And Comebacks": MAcular = Mucopolysaccharide (Alcian blue); Granular = Hyaline (Masson trichrome); LAttice = Amyloid (Congo red). Morning blur is pathognomonic for Fuchs.

Differential Diagnosis

  • Corneal degeneration (arcus senilis, Salzmann nodular)
  • Pseudophakic bullous keratopathy (usually unilateral)
  • ICE syndrome (unilateral with iris changes)
  • Interstitial keratitis
  • Post-infectious corneal scar

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