Condition (arrow)of the iris is defined as:
A. Persistent anterior vascular sheath of lens
B. Absent iris
C. Failure of Choroidal tissue to close completely
D. Pink coloured iris
Ans:C. Poorly developed choroidal tissues
This condition is Coloboma
- It is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc.
- It is typically located in the inferonasal quadrant of the involved structure
- The hole is present from birth and can be caused when choroid fissure which generally closes by the seventh week of pregnancy fails to close up completely before a child is born.
- Most cases of coloboma affect only the iris.
- The effects a coloboma has on the vision can be mild or more severe depending on the size and location of the gap.
- If, for example, only a small part of the iris is missing, vision may be normal, whereas if a large part of the retina or optic nerve is missing, vision may be poor and a large part of the visual field may be missing
- Continued existence of part of the anterior vascular sheath of the lens (a foetal structure which normally disappears shortly before birth) is known as persistent pupillary membrane
- Absence of iris is known as aniridia
- Owing to the absence of the pigment in the eye in patients of albinism, iris looks pink