Question

Iris of an eye is an extension of
A. ornea
B. Sclerotic
C. Retina
D. Choroid

Answer 1

The iris is the muscular diaphragm that allows and controls the amount of light entering the eye. It adjusts the size of the pupil. It is controlled involuntarily. Iris is the colored part of the eye. In the presence of the bright light, the iris closes the pupil to let in less light. And in the presence of low light, the iris opens up the pupil to let in more light.

Complete answer:
• The human eye has three distinct layers, the outer, middle, and inner ones. The middle layer of the eye consists of three components that are choroid, ciliary body, and iris.
• The choroid is a thin vascular layer that is dark pigmented. The thickening of the choroid in the anterior forms the ciliary body. When seen from the front, the choroid becomes a doughnut-shaped iris which is the colored part of the eye.
• The iris regulates and controls the size of the pupil.
• The choroid is continuous with the iris; the choroid and iris together are called the uvea. Retina covers the posterior surface of the iris.
• The inner layer of the retina, called the posterior epithelium of the iris is the layer facing the posterior chamber, and the retinal pigment epithelium which is the outermost layer of the retina is tightly attached to the choroid. Both layers of the retina are pigmented. The pigmentation is heavier in the inner layer.
• The transparent part of the eye is called the cornea. It covers the front portion of the eye.
Sclerotic or the sclera is the white part of the eye that surrounds the cornea.

Hence, the correct answer is option (D).

Note: Iris is responsible for regulating the size of the pupil by controlling the amount of light entering the eye. Nourishment and oxygen to the outer layers of the retina are provided by the Choroid. The ciliary body and iris, along with the choroid form the uveal tract. The choroid’s function is to provide nutrition for the retina and to convey vessels and nerves to the ciliary body and iris.