COLOBOMA OF THE OPTIC DISC
It due to the failure in closure of the embryonic
fissure. It occurs in two forms.
The minor defect is
more common and manifests as inferior crescent,
usually in association with hypermetropic or
astigmatic refractive error.
The fully-developed
coloboma typically presents inferonasally as a very
large whitish excavation, which apparently looks as
the optic disc. The actual optic disc is seen as a linear
horizontal pinkish band confined to a small superior
wedge.
Defective vision and a superior visual field
defect is usually associated.