Pathology of cornea 2

1. PATHOLOGY OF CORNEA
OPTOM FASLU MUHAMMED

2. ANATOMY
 an average horizontal diameter - 11.7 mm
vertical diameter - 11 mm.
 The posterior surface of cornea is circular with an
average diameter of 11.5 mm.
 Thickness of cornea in the centre - 0.52 mm
at the periphery - 0.7 mm.
 anterior radius of curvature - 7.8 mm
 Posterior radius of curvature - 6.5 mm

3. LAYERS OF CORNEA

4.  Blood supply
 Cornea is an avascular - Small loops derived from the
anterior ciliary vessels invade its periphery for about 1
mm
Nerve supply
 Cornea is supplied by anterior ciliary nerves which are
branches of ophthalmic division of the 5th cranial nerve.

5. PHYSIOLOGY
1. to act as a major refracting medium
2. to protect the intraocular contents.
Corneal transparency
 Peculiar arrangement of corneal lamellae
 Avascularity
 Relative state of dehydration
 active bicarbonate pump of the Endothelium.

6. SOURCE OF NUTRIENTS
 1. Solutes (glucose and others) enter the cornea by
either simple diffusion or active transport through
aqueous humor and by diffusion from the perilimbal
capillaries.
 2. Oxygen is derived directly from air through the
tear film.

7. CONGENITAL ANOMALIES
 Megalocornea
 Megalocornea is labelled when the
horizontal diameter of cornea is of adult size at
birth 13 mm or greater after the age of 2 years. The
cornea is usually clear with normal thickness and
vision.

9.  Differential diagnosis
 Buphthalmos. In this condition IOP is raised and the
eyeball is enlarged as a whole.
 Keratoglobus. In this condition, there is thinning and
excessive protrusion of cornea, which seems
enlarged; but its diameter is usually normal

10. MICROCORNEA
 In microcornea, the horizontal diameter is less than 10
mm since birth. The condition may occur as in
association with
 nanophthalmos (normal small eyeball) or
 microphthalmos (abnormal small eyeball).

12. CORNEA PLANA
 This is a rare anomaly in which bilaterally cornea is
comparatively flat since birth.
 It may be associated with microcornea. Cornea
plana usually results in marked astigmatic refractive
error.

14. CONGENITAL CLOUDY CORNEA
 Sclerocornea
 Tears in Decrement's membrane
 Ulcer
 Metabolic conditions
 Posterior corneal defect
 Endothelial dystrophy
 Dermoid