Question

The eyeball is approximately spherical in shape. What is the diameter of the normal human eyeball?
A. Approximately 2.3 cm
B. Approximately 4.3 cm
C. Approximately 5.3 cm
D. None of the above

Answer 1

Hint: The human eye is an organ of the senses which reacts to light and allows vision. Rod and cone photoreceptor cells enable the perception and vision of conscious light including colour differentiation and depth perception.

Complete Step-by-Step solution:


The human eye is an organ of the senses which reacts to light and allows vision. Rod and cone photoreceptor cells enable the perception and vision of conscious light including colour differentiation and depth perception.
The human eye is one of the most important and sensitive organs of the senses. Colours cannot be detected when shutting the eyes. Thus, the human eye is the most important of all the sense organs because it helps us to see the magnificent, vibrant world around us. The human eye resembles a mirror. Its lens system forms an image, called the retina, on a light sensitive screen. A thin layer called the cornea carries light into the eye. It constructs the clear bulge across the front eyeball surface. The eyeball is spherical in shape with even a diameter of about 2.3 cm. Most of the refraction for the light rays happens on the outer cornea surface.
The eye is not shaped like a circular circle, but it is a two-piece fused structure, consisting of an anterior segment (front) and the posterior segment (back). The cornea, iris, and lens form the anterior segment. The cornea is translucent and more angled and is connected to the larger rear section, which consists of the vitreous, retina, choroid and the sclera called the outer white shell.
The human eye can distinguish between around 10 million colours, and can detect a single photon. The pupil forms part of the sensory nervous system.
Hence, option A is the correct option. The diameter of the normal human eyeball is 2.3 cm.

Note: Similar to other mammals' eyes, the non-image-forming photosensitive ganglion cells of the human eye in the retina receive light signals that influence adjustment of the pupil's size, control and suppression of the hormone melatonin, and body clock entrainment.