CONGENITAL ANOMALIES
Megalocornea
Horizontal diameter of cornea at birth is about 10 mm and the adult size of about 11.7 mm is attained by the
age of 2 years.
Megalocornea is labelled when the horizontal diameter of cornea is of adult size at birth or 13 mm or greater after the age of 2 years. The cornea is usually clear with normal thickness and vision. The condition is not progressive. Systemic association include Marfan's, Apert, Ehlers Danlos and Down
syndromes.
Differential diagnosis
1. Buphthalmos.
In this condition IOP is raised and the eyeball is enlarged as a whole. The enlarged cornea is usually associated with central or peripheral clouding and Descemet's tears (Haab's
striae).
2. Keratoglobus.
In this condition, there is thinning and excessive protrusion of cornea, which seems enlarged; but its diameter is usually normal.
Microcornea
In microcornea, the horizontal diameter is less than 10 mm since birth. The condition may occur as an isolated anomaly (rarely) or in association with nanophthalmos (normal small eyeball) or microphthalmos (abnormal small eyeball).
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.
Congenital cloudy cornea
The acronym 'STUMPED' helps to remember the common conditions to be included in differential diagnosis of neonatal cloudy cornea.
The conditions are as follows:
� Sclerocornea
� Tears in Descemet's membrane
� Ulcer
� Metabolic conditions
� Posterior corneal defect
� Endothelial dystrophy
� Dermoid