Ophthalmology/Diseases of Cornea

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Introduction to Cornea[edit | edit source]

The cornea is a transparent, avascular, watch-glass like structure. It forms anterior 1/6th of the outer fibrous coat of eyeball.

Functions[edit | edit source]

  1. Major refracting medium
  2. Protects intraocular contents

Applied Physiology[edit | edit source]

Corneal Transparency[edit | edit source]

It is due to the following factors:

  1. Peculiar arrangement of corneal lamellae (Lattice Theory of Maurice)
  2. Avascularity
  3. Relative state of dehydration maintained by barrier effects of epithelium and endothelium and active bicarbonate pump of endothelium

Source of Nutrients[edit | edit source]

Solutes enter the cornea by:

  • Simple diffusion through aqueous humor
  • Active transport through aqueous humor
  • Diffusion from perilimbal capillaries

Oxygen directly enters from the air via an active process of epithelium

Congenital Anomalies[edit | edit source]

Megalocornea[edit | edit source]

When the horizontal diameter of cornea is of adult size at birth or 13mm or greater after the age of 2 years.

Microcornea[edit | edit source]

When the horizontal diameter is less than 10mm since birth.

Cornea Plana[edit | edit source]

Bilaterally the cornea is comparatively flat in this condition.

Congenital Cloudy Cornea[edit | edit source]

Cloudiness in the cornea since birth due to generally

  1. Sclerocornea
  2. Tears in Descemet's membrane
  3. Ulcer
  4. Metabolic conditions
  5. Posterior Corneal Defect
  6. Endothelial dystrophy
  7. Dermoids

Inflammatory Conditions[edit | edit source]

The inflammation of cornea is called keratitis.

Morphological Classification[edit | edit source]

A. Ulcerative Keratitis (corneal ulcer)

  1. Depending on location
    1. Central
    2. Peripheral
  2. Depending on purulence
    1. Purulent Corneal Ulcer (suppurative)
    2. Non-Purulent Corneal Ulcer (non-suppurative)
  3. Depending on hypopoyon
    1. Simple Corneal Ulcer
    2. Hypopyon Corneal Ulcer
  4. Depending on Depth
    1. Superficial
    2. Deep
    3. Impending perforation
    4. Perforated
  5. Depending on Slough fornmation
    1. Non-Sloughing Corneal Ulcer
    2. Sloughing Corneal Ulcer

B. Non-Ulcerative Keratitis

  1. Superficial keratitis
    1. Diffuse superficial keratitis
    2. Superficial Punctate Keratitis (SPK)
  2. Deep Keratitis
    1. Non-suppurative
      1. Interstitial
      2. Disciform
      3. Sclerosing
      4. Keratitis Profunda
    2. Suppurative
      1. Central Corneal
      2. Posterior Corneal

Etiological Classification[edit | edit source]

  1. Infective keratitis
    1. Bacterial
    2. Viral
    3. Fungal
    4. Chlamydial
    5. Protozoal
    6. Spirochaetal
  2. Allergic Keratitis
    1. Phlyctenular keratitis
    2. Vernal keratitis
    3. Atopic keratitis
  3. Trophic Keratitis
    1. Exposure keratitis
    2. Neuroparalytic keratitis
    3. Keratomalacia
    4. Atheromatous Ulcer
  4. Associated with diseases of skin and mucous membrane
  5. Associated with systemic collagen vascular disorders
  6. Traumatic keratitis
  7. Idiopathic keratitis
    1. Mooren's Corneal Ulcer
    2. Superior limbic keratoconjunctivitis
    3. Thygseon's superficial punctate keratitis

Degenerative Disorders[edit | edit source]

It happens when normal corneal cells undergo some degenerative changes due to age or some pathological conditions.

Classification[edit | edit source]

A.Etiological Classification

  1. Age related degenerations
    1. Arcus senilitis
    2. Vogt's white limbal girdle
    3. Hassal-Henle bodies
    4. Mosaic degeneration
  2. Pathological degenerations
    1. Fatty degeneration
    2. Amyloidosis
    3. Calcific degeneration
    4. Salzmann's nodular degeneration
    5. Furrow degeneration
    6. Spheroidal degeneration
    7. Pellucid marginal degeneration
    8. Terrien's marginal degeneration
    9. Mooren's ulcer

Corneal Dystrophies[edit | edit source]

These are inherited disorders in which the cells have some inborn defects due to which cornea becomes hazy with the passage of time. There is no associated systemic pathology.

Classification[edit | edit source]

  1. Anterior Dystrophies
    1. Epithelial basement membrane dystrophy
    2. Reis-Buckler's Dystrophy
    3. Meesman's Dystrophy
    4. Recurrent Corneal Erosion Syndrome
    5. Stocker-Holt Dystrophy
  1. Stromal Dystrophies
    1. Lattice Dystrophy
    2. Crystalline Dystrophy (Schnyder's)
    3. Granular Dystrophy (Groenouw's type I)
    4. Macular Dystrophy (Groenouw's type II)
  1. Posterior Dystrophies
    1. Cornea Gutta
    2. Fuch's late hereditary endothelial dystrophy
    3. Posterior polymorphous dystrophy (of Schlichting)
    4. Congenital hereditary endothelial dystrophy (CHED)

Ectatic Conditions[edit | edit source]

  • Keratconus: is a non-inflammatory, mostly bilateral, ectatic condition of cornea in it's axial part.
  • Keratoglobus: It is a familial and hereditary bilateral congenital disorder characterized by thinning and hemispherical protrusion of the entire cornea.
  • Keratoconus Posterior: Extremely rare condition. Cone-like bulging of posterior surface of cornea occurs.

Abnormalities in transparency of cornea[edit | edit source]

Any condition that alters corneal transparency leads to loss of vision. The most common causes of loss of corneal transparency are:

  1. Corneal Oedema
  2. Drying of Cornea
  3. Depositions on Cornea
  4. Inflammations of Cornea
  5. Corneal Degenerations
  6. Dystrophies of cornea
  7. Vascularization of cornea
  8. Scarring of Cornea

Corneal Opacities[edit | edit source]

This term is typically used for the loss of transarency of cornea due to scarring.


  1. Developemental Anomalies
  2. Following birth trauma
  3. Healed Corneal wounds
  4. Healed Corneal Ulcers

Corneal Oedema[edit | edit source]

Normal water content of cornea is 78%. If it becomes greater than this, central thickness increases and transparency reduces.slit lamp examination shows hazy cornea.


  1. Raised IOP
  2. Endothelial damage
  3. Epithelial damage

one drop of glycerine clears the hazy appearance of the cornea

Vasclarization of Cornea[edit | edit source]

Normally the cornea has only small capillary loops in the periphery for about 1mm. It can be invaded by vessels leading to irritation and decreased corneal transpaency.