Sclera

Aka: Sclera, Scleral Icterus, Yellow Sclera, Episclera, Lamina Cribrosa

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II. Physiology

  1. Sclera
    1. Thick, protective outer coat of the eye underlying the Conjunctiva
    2. Poorly vascularized
    3. Normally white (with possible bluish discoloration) and opaque
    4. Scleral inflammation is very painful, and associated with Vision Loss
  2. Episclera
    1. Covers the anterior Sclera and lacks the Scleral bluish discoloration
    2. Continuous with the Cornea
    3. Episcleral inflammation is not typically painful, and does not cause Vision change
  3. Lamina Cribrosa of Sclera
    1. Sleeve-like space at the opening of the Sclera through which Retinal axons pass on their way to the Optic Nerve
    2. Represents hundreds of openings through which 1-2 Million nerves pass (bundled into groups)
    3. Retinal axons are particularly sensitive to injury at the lamina cribosa, where the axons bend and exit the eye
      1. Lamina Cribrosa is an important landmark for Glaucoma related-injury to Retinal axons

III. Findings: Normal

  1. Normally white and opaque

IV. Causes: Scleral Inflammation

  1. Scleritis
  2. Episcleritis

V. Causes: Scleral Discoloration

  1. Blue Sclera suggests Osteogenesis Imperfecta
  2. Yellow Sclera Causes
    1. Carotenemia does not involve the Sclera
    2. Scleral Icterus
      1. Hyperbilirubinemia (associated with Jaundice)
      2. Bilirubin uniformly deposits throughout Sclera
    3. Quinacrine
      1. Yellow discoloration near limbus
    4. Yellow subscleral fat (normal)
      1. Involves only the area farthest from the limbus

VI. Reference

  1. Degowin (1987) Bedside Diagnostic Exam, p. 480

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