Retina
Cornea
Choroids
Sclerotic
Eye Structure by CSS Exam Desk Team
- The human eye is one of the most valuable and sensitive sense organs. It is like a camera.
- Retina: Within the human eye, the lens system of eyes forms an image on a light-sensitive screen called the retina. The retina contains several nerve cells.
- Optical nerve: Within the human eye, sensations felt by the nerve cells are then transmitted to the brain through the optic nerve.
- There are two kinds of cells:- (i) Cones: These are sensitive to bright light. Cones sense color. (ii) Rods: These are sensitive to dim light.
- Blind spot: Within the human eye, at the junction of the optic nerve and the retina, there are no sensory cells, so no vision is possible at that spot. This is called the blind spot.
- The impression of an image does not vanish immediately from the retina. It persists there for about 1/16th of a second. So, if still images of a moving object are flashed on the eye at a rate faster than 16 per second, then the eye perceives this object as moving.
- Cornea: Light enters the eye through a thin membrane called the cornea. It forms a transparent bulge on the front surface of the eyeball. The eyeball is approximately spherical in shape with a diameter of about 2.3 cm. Most of the refraction for the light rays entering the eye occurs at the outer surface of the cornea.
- Iris: It is behind the cornea. It is a dark muscular diaphragm that controls the size of the pupil.
- Pupil: Within the human eye, it regulates and controls the amount of light entering the eye.
- Eye lens: It forms an inverted real image of the object on the retina. The retina is a delicate membrane having an enormous number of light-sensitive cells. The light-sensitive cells get activated upon illumination and generate electrical signals. These signals are sent to the brain via the optic nerves. The brain interprets these signals, and finally, processes the information so that we perceive objects as they are.
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