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Crystalline Keratopathy

ROUTINE — Cornea

Symptoms

Decreased vision (proportional to plaque density/location).

Photophobia.

Decreased corneal sensation (in certain etiologies).

Often asymptomatic; biofilm-sequestered organisms may not provoke typical pain or photophobia.

Clinical Findings

Infectious crystalline keratopathy (ICK)

  • Fine, white, branching, "snowflake" or "fern-like" stromal opacities.
  • Key Diagnostic Clue: Significant disconnect between dense stromal infiltrate and a quiet, noninflamed eye.
  • Organisms are sequestered within an exopolysaccharide biofilm, shielding them from host immunity and antibiotics.

Clinical settings for ICK

  • Post-Penetrating Keratoplasty (PKP): Develops months to years later, usually on chronic topical steroids.
  • Suture Tracks: Crystals propagate along sutures, which act as a biofilm scaffold and portal of entry.
  • Other: Chronic contact lens wear, neurotrophic keratopathy, or post-refractive surgery interfaces.

Causative organisms

  • Streptococcus viridans (mitis group): Most common (>70%); produces glycocalyx biofilm.
  • Others: Coagulase-negative Staph, Haemophilus, Pseudomonas, Atypical Mycobacteria (post-LASIK).
  • Fungal: Candida, Alternaria.

Non-infectious crystals

  • Schnyder Dystrophy: Cholesterol/phospholipid deposits; associated with hyperlipidemia.
  • Cystinosis: Polychromatic fine stromal crystals; associated with renal failure in children.
  • Dysproteinemias: Multiple myeloma, MGUS, or Waldenström (diffuse fine stromal crystals).
  • Bietti Dystrophy: Sparking yellow-white spots at the corneal limbus.
  • Drug Deposition: Amiodarone, tamoxifen, or ciprofloxacin precipitates.

Etiology

Infectious mechanism

  • Biofilm formation on collagen or surgical hardware (sutures/flaps).
  • Chronic topical steroid use is the primary permissive factor.

Systemic & metabolic

  • Schnyder: Autosomal dominant (AD) disorder of local corneal lipid metabolism.
  • Cystinosis: Autosomal recessive (AR) systemic metabolic defect.
  • Lymphoproliferative: Paraprotein deposition (Multiple Myeloma, cryoglobulinemia).
  • Bietti: AR retinal and corneal crystalline dystrophy.

Red Flags

Crystalline deposits post-PKP → suspect Strep viridans ICK; mandates prolonged fortified antibiotics.

Bilateral crystals in an adult → perform SPEP/UPEP to rule out Multiple Myeloma.

Crystals in a child → rule out Systemic Cystinosis (potentially fatal without renal management).

Progression despite antibiotics → consider atypical mycobacteria or surgical debulking.

Investigations

Infectious workup

  • Corneal cultures (bacterial and fungal).
  • Mycobacterial cultures and acid-fast stains (especially for post-refractive surgery patients).
  • Confocal microscopy: May visualize branching crystalline patterns.

Systemic workup (non-infectious)

  • Schnyder: Fasting lipid profile.
  • Bietti: Electroretinogram (ERG).
  • Cystinosis: Conjunctival biopsy, blood/bone marrow smear, and pediatric nephrology consult.

Dysproteinemia workup

  • Serum Protein Electrophoresis (SPEP) and Urine Protein Electrophoresis (UPEP).
  • Free light chains, CBC with differential, serum calcium, and creatinine.

Treatment

Infectious crystalline keratopathy

  • Fortified Antibiotics: Topical Vancomycin (25–50 mg/mL) + Cefazolin (50 mg/mL) or Moxifloxacin.
  • Frequency: Hourly initially; taper very slowly over weeks to months.
  • Steroids: Reduce frequency or strength slowly (do not stop abruptly).
  • Surgical: Suture removal, plaque debulking, or intrastromal antibiotic injections for resistant biofilm.

Systemic & dystrophic causes

  • Cystinosis: Topical cysteamine drops (dissolves crystals) and systemic cysteamine.
  • Schnyder: Manage hyperlipidemia; consider lamellar or penetrating keratoplasty.
  • Paraproteinemia: Treat the underlying hematologic malignancy.

Clinical Pearl

Branching corneal crystals are a major clinical "tell"—they can be the first sign of multiple myeloma or MGUS years before systemic symptoms appear. In post-graft patients, the "fern-like" infiltrate in a quiet eye is Strep viridans ICK until proven otherwise.

Differential Diagnosis

  • Infectious crystalline keratopathy (Strep viridans)
  • Band keratopathy
  • Granular corneal dystrophy
  • Cystinosis
  • Paraproteinemia (Multiple Myeloma)

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