Anatomy Of Cornea

Anatomy Of Cornea


Anatomy Of Cornea

  • Outer & fibrous coat of EYEBALL.
  • Transparent, anterior 1/6th segment of eyeball.
  • Non-vascular
  • Watch- glass like structure.
  • The charaterstics of adult cornea are:
1. Surfaces: Has two surfaces, anterior & posterior.
  • Anterior surface is elliptical, posterior surface is circular.
  • Horizontal diameter of both surfaces is same (11.7 mm).
  • While vertical diameter of posterior surface (11.7 mm) is about 1 mm less than anterior surface (10.6 mm).
  • Radius of curvature of anterior surface is 7.8 mm & of posterior surface is 6.5 mm.
  • The vertical meridian of cornea is 0.05 D steeper than the horizontal meridian, resulting in Astigmatism with the rule.
2. Refractive power:
  • Refractive power of cornea is about 43-44 D (3/4 of total diopetric power of the eye).
  • Most of the refraction in eye occur at anterior surface of cornea (air-tear interface) ,i.e., Anterior surface of cornea is the most important refractive structure of eye.
  • Refractive index of Cornea is 1.376.
3. Change in size:
  • Horizontal diameter of cornea at birth is about 10 mm & the adult 11.7mm is attained by the age of 2 years.
  • Megalocornea is labelled when the horizontal diameter is of adult size at birth or ≥ 13 mm afterthe age of 2 years.
  • Systemic diseases associated with megalcornea are Marfan syndrome, Ehler danlos syndrome, Apert syndrome & Down syndrome.
  • Microcornia is labelled when the corneal diameter is < 10mm.
METABOLISM & SOURCE OF NUTRITION
  • Cornea requires energy for maintenance of its transparency and state of relative dehydration.
  • Energy in form of ATP is generated by the breakdown of glucose.
  • As cornea is is an avascular structure, major pathway of metabolism is anaerobic glycolysis.
  • The most actively metabolising layers of the cornea are epithelium & endotheium the former being ten times thicker than the latter, requires a proportionately large supply of metabolic substrates.

Cornea is avascular structure. Source of nutrition are:

  1.  Solutes (glucose & other): From aqueous humor & perilimbal capillaries.
  2. Oxygen: From air (atmosphere) through the tear film.

Exam Question

  • Avascular coat in eye is Cornea.
  • Anterior surface of Cornea is elliptical, posterior surface is circular.
  • Radius of curvature of anterior surface of Cornea is 7.8 mm
  • Refractive power of cornea is about 43-44 D.
  • Refractive index of Cornea is 1.376.
  • Most of the refraction in eye occur at anterior surface of cornea (air-tear interface).
  • The critical angel of cornea-air interface is 46°.
  • Cornea gets its nourishment mainly from Aqueous humour.
Don’t Forget to Solve all the previous Year Question asked on Anatomy Of Cornea

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this:
Malcare WordPress Security