Cornea and Corneal Problems in Optometry
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Cornea and Corneal Problems in Optometry

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Questions and Answers

What is the thickness of the epithelium layer in the cornea?

  • 50um (correct)
  • 500um
  • 10-20um
  • 1-2mm

    • What is the primary component of the stroma layer in the cornea?

  • Keratocytes
  • Endothelial cells
  • Epithelial cells
  • Type 1 collagen and proteoglycans (correct)

    • What is the primary function of the endothelium layer in the cornea?

  • To regulate fluid balance
  • To facilitate nutrient exchange
  • To provide mechanical strength to the cornea
  • To enlarge to account for cell loss (correct)

    • What is the average radius of curvature of the cornea?

    <p>7.8mm</p> Signup and view all the answers

    What is the wavelength of light at which light transmission is maximal through the cornea?

    <p>700nm</p> Signup and view all the answers

    What is the typical refractive index of the cornea?

    <p>1.3375</p> Signup and view all the answers

    What is the typical location of the crescent-shaped area of inferior corneal thinning in high increasing regular astigmatism?

    <p>From 4 to 8 o'clock</p> Signup and view all the answers

    What is the most common peripheral corneal opacity?

    <p>Arcus Senilus</p> Signup and view all the answers

    What is the characteristic appearance of Cornea Guttata?

    <p>All of the above</p> Signup and view all the answers

    What is the treatment for Band Keratopathy?

    <p>Chelation or excimer laser</p> Signup and view all the answers

    What is the typical age of onset for Meesman dystrophy?

    <p>First decade of life</p> Signup and view all the answers

    What is the characteristic of Lipid Keratopathy?

    <p>Abnormal vessels leak lipid into the stroma</p> Signup and view all the answers

    Which type of lattice dystrophy is associated with progressive facial palsy and systemic features?

    <p>Lattice Dystrophy Type 2</p> Signup and view all the answers

    What is the characteristic appearance of Cogan Microcystic dystrophy?

    <p>Map Dot Fingerprint or epithelial basement membrane appearance</p> Signup and view all the answers

    What is the typical appearance of the opacities in Granular Dystrophy Type 1?

    <p>White snowflake-like opacities in the stroma</p> Signup and view all the answers

    What is the characteristic of Reis-Bucklers dystrophy?

    <p>Honeycomb or fishnet appearance</p> Signup and view all the answers

    What is the metabolic dysfunction in Macular Dystrophy Types 1 and 2?

    <p>Failure to produce keratan sulphate</p> Signup and view all the answers

    What is the treatment for Reis-Bucklers dystrophy?

    <p>Lamellar keratoplasty</p> Signup and view all the answers

    What is the characteristic of Meesman dystrophy?

    <p>Very rare and autosomal dominant</p> Signup and view all the answers

    Which type of dystrophy is characterized by central corneal haze and scintillating subepithelial crystalline opacities?

    <p>Schnyder dystrophy</p> Signup and view all the answers

    What is the characteristic of Corneal Dystrophies?

    <p>Tend to develop slowly through life</p> Signup and view all the answers

    What is the typical age of onset for Lattice Dystrophy Type 3?

    <p>Fourth decade of life</p> Signup and view all the answers

    What is the characteristic shape of the corneal protrusion in keratoconus?

    <p>Oval or nipple</p> Signup and view all the answers

    What is the purpose of riboflavin drops in corneal collagen crosslinking?

    <p>To promote collagen crosslinking</p> Signup and view all the answers

    What is the typical appearance of the opacities in Granular Dystrophy Type 3?

    <p>A few superficial and small white ring-shaped lesions</p> Signup and view all the answers

    What is the typical feature of Fuch's Endothelial Dystrophy?

    <p>Greatly thickened Descemet's membrane</p> Signup and view all the answers

    What is the typical location of cones in keratoconus?

    <p>Inferior</p> Signup and view all the answers

    What is the term for the break or fold in Descemet's membrane?

    <p>Break in Descemet's membrane</p> Signup and view all the answers

    What is the typical treatment for Lattice Dystrophy Type 1?

    <p>Penetrating keratoplasty</p> Signup and view all the answers

    Which type of dystrophy is characterized by the presence of subepithelial dots that coalesce into fine spidery branching lattice lines?

    <p>Lattice Dystrophy Type 1</p> Signup and view all the answers

    What is the name of the clinical sign characterized by bulging of the lower lid on downgaze?

    <p>Munson's sign</p> Signup and view all the answers

    What is the purpose of INTACS in keratoconus treatment?

    <p>To strengthen the cornea</p> Signup and view all the answers

    What is the typical age of onset for keratoglobus?

    <p>At birth</p> Signup and view all the answers

    What is the name of the degeneration of collagen fibers in conjunctival stroma?

    <p>Pinguecula</p> Signup and view all the answers

    What is the term for the iron deposits that accumulate around the base of the cone in keratoconus?

    <p>Fleischer's ring</p> Signup and view all the answers

    What is the percentage of keratoconus cases that require penetrating keratoplasty or epikeratoplasty?

    <p>10-20%</p> Signup and view all the answers

    What is the primary characteristic of Stage 1 Fuch's Endothelial Dystrophy?

    <p>Central posterior cornea shows guttata changes and pigment dusting</p> Signup and view all the answers

    What is the name of the condition characterized by subtle vesicular, geographical or band-like lesions on endothelium?

    <p>Posterior Polymorphous Dystrophy</p> Signup and view all the answers

    What is the treatment for Exposure Keratopathy?

    <p>Hydrate the cornea with artificial tears/ointment, taping eye closed, and tarsorrhaphy</p> Signup and view all the answers

    What is the cause of Neurotrophic Keratopathy?

    <p>Loss of nerve supply to the cornea</p> Signup and view all the answers

    What is the characteristic of Recurrent Corneal Erosion Syndrome?

    <p>Defective adhesion of epithelium to Bowman's layer</p> Signup and view all the answers

    What is the treatment for Thygeson Superficial Punctate Keratitis?

    <p>Relieve symptoms with lubrication and topical steroid</p> Signup and view all the answers

    What is the type of keratopathy characterized by gold in the stroma?

    <p>Chrysiasis</p> Signup and view all the answers

    What is the stage of Fuch's Endothelial Dystrophy characterized by less pain and collagen deposition?

    <p>Stage 3</p> Signup and view all the answers

    What is the type of keratopathy characterized by recurrent breakdown of the epithelium?

    <p>Recurrent Corneal Erosion Syndrome</p> Signup and view all the answers

    What is the congenital disease characterized by subtle vesicular, geographical or band-like lesions on endothelium?

    <p>Posterior Polymorphous Dystrophy</p> Signup and view all the answers

    What is the name of the disease characterized by glycolipidosis, purple skin lesions, cardio and renal lesions, and pain in fingers and toes?

    <p>Fabry disease</p> Signup and view all the answers

    What is the purpose of refractive surgery?

    <p>To correct refractive errors such as myopia and hyperopia</p> Signup and view all the answers

    What is the name of the procedure where a full-thickness corneal graft is transplanted?

    <p>Penetrating keratoplasty</p> Signup and view all the answers

    What is the name of the condition characterized by symmetrical, bilateral, grey/golden deposits in the epithelium?

    <p>Vortex keratopathy</p> Signup and view all the answers

    What is the name of the technique used to remove a metallic or stone foreign body from the cornea?

    <p>Using the tip of a hyperdermic needle</p> Signup and view all the answers

    What is the name of the symptom complex characterized by watering, reduced vision, photophobia, and pain?

    <p>Corneal abrasion</p> Signup and view all the answers

    What is the purpose of topical cycloplegia in the management of corneal abrasion?

    <p>To reduce pain</p> Signup and view all the answers

    What is the name of the procedure that involves transplanting a partial-thickness corneal graft?

    <p>Lamellar keratoplasty</p> Signup and view all the answers

    What is the name of the condition characterized by deposition of copper in tissues, resulting in a sunflower lens opacity?

    <p>Wilson disease</p> Signup and view all the answers

    What is the purpose of careful examination in the management of ocular foreign body?

    <p>All of the above</p> Signup and view all the answers

    Study Notes

    Corneal Anatomy

    • The cornea is composed of five layers:
      • Epithelium (50um thick, with basal, wing, and desquamating cells)
      • Bowman's layer (10-20um thick)
      • Stroma (accounts for over 90% of corneal thickness, contains keratocytes, type 1 collagen, and proteoglycans)
      • Descemet's membrane
      • Endothelium (single layer of cells that don't replicate, but enlarge to account for cell loss)

    Corneal Examination

    • Slit lamp examination: several illumination techniques
    • Keratometer/keratoscopy: measures corneal curvature
    • Corneal topographer: maps corneal surface
    • Specular microscope: examines endothelial cells
    • Pachymetry: measures corneal thickness

    Normal Corneal Parameters

    • Horizontal diameter: 11-12mm
    • Vertical diameter: 9-11mm
    • Central thickness: 500um
    • Peripheral thickness: 650um
    • Refractive index: 1.3375
    • Average radius of curvature: about 7.8mm (+43D)
    • Light transmission: maximal at 700nm (98%), decreases to 80% at 400nm

    Corneal Problems

    • Clinical signs: punctate epitheliopathy, epithelial oedema, corneal filaments, stromal infiltrates, stromal oedema, stromal vascularisation, breaks/folds in Descemet's membrane, endothelial problems
    • Chronic signs: neovascularisation, scarring

    Corneal Ectasias

    • Keratoconus: thinning and ectasia of the cornea, central and paracentral stromal thinning, apical protrusion, and irregular astigmatism
    • Keratoconus associations: Leber congenital amaurosis, retinitis pigmentosa, aniridia, etc.
    • Autosomal dominant inheritance with variable penetrance
    • Signs: scissor reflex on retinoscopy, irregular astigmatism, fine deep stromal striae (Vogt's lines), progressive corneal thinning, steep keratometry measurements, bulging of the lower lid on downgaze (Munson's sign), epithelial iron deposits around the base of the cone (Fleischer's ring)
    • Keratoconus treatment: spectacles, RGP contact lenses, scleral contact lenses, intra-stromal rings (INTACS), epikeratoplasty or penetrating keratoplasty, corneal collagen crosslinking (CXL)

    Corneal Degenerations

    • Arcus senilis: most common peripheral corneal opacity, hyperlipoproteinaemia frequently associated, bilateral lipid deposition starting in the superior and inferior perilimbal cornea
    • Vogt's white limbal girdle: very common, harmless, age-related finding, bilateral narrow crescentic lines composed of chalk-like flecks at the interpalpebral fissure on the nasal and temporal limbus
    • Crocodile shagreen: greyish-white polygonal stromal opacities, separate by clear spaces, rarely the opacities are found more posteriorly
    • Cornea guttata: focal accumulations of collagen on the posterior surface of Descemet's membrane, 'raindrops on a windowpane' or 'beaten metal' appearance
    • Band keratopathy: deposition of Ca+ salts in subepithelial space, anterior Bowman's layer, and anterior stroma, can arise from ocular conditions, metabolic conditions, or be hereditary

    Corneal Dystrophies

    • Most inherited abnormalities, bilateral, tend to develop slowly through life (progressive)
    • Dystrophies which predominantly involve the epithelium and anterior stroma tend to present with recurrent epithelial erosions and worsening vision from subsequent scarring
    • Types of corneal dystrophies:
      • Cogan microcystic dystrophy
      • Reis-Bucklers dystrophy
      • Meesman dystrophy
      • Schnyder dystrophy
      • Lattice dystrophy (Types 1, 2, and 3)
      • Granular dystrophy (Types 1, 2, and 3)
      • Macular dystrophy (Types 1 and 2)
      • Fuch's endothelial dystrophy
      • Posterior polymorphous dystrophy

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    Description

    Test your knowledge of corneal anatomy, signs and symptoms of corneal problems, corneal ectasias, degenerations, dystrophies, and surgical interventions. Also, covers corneal foreign bodies and abrasions.

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