The human eye is one of the most important and sensitive sense organs. It helps us to see the wonderful world and the colors around us. The human eye is a paired sense organ that uses light and enables us to see objects around us. After closing the eyes, we can identify some objects to some extent by their taste smell, taste, the sound they make, or touch. It is, however, impossible to identify
colors while closing the eyes. Thus, the human eye
is the gateway to one of our five senses. The human eye is like a camera. The
human eye is a slightly asymmetrical globe about an inch in diameter. The part of
our eyes includes: Iris –the colored part which is behind the cornea that
controls the size of the pupil, the eye lens forms an inverted real image on a
light-sensitive screen called the retina. Light enters the eye through a thin
membrane called the cornea which makes a clear dome over the iris. It forms the
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.
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.
DEFECTS OF VISION AND THEIR CORRECTION
Sometimes, the
eye of a person may get compromised and lose its power. In such a condition, the
person cannot see the object perfectly or it gets blurred. The main reason
behind this is the refractive defects of the eye.
Let’s see some
common problems that a person may suffer with.
1.
Myopia –Myopia is also known as
near-sightedness. A person with myopia can see nearby objects clearly but cannot
see distant objects distinctly. A person with this defect has the far
point nearer than infinity. Such a person may see clearly to a distance of a few meters. In a myopic eye, the image of a distant object is formed in front of the retina and not at the retina itself because the eye is “too long” for the lens. This defect can be corrected by using a concave lens of suitable power. .A concave lens of suitable power will bring the image back onto the retina.
2. Hypermetropia –Hypermetropia is also known as far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. It can happen when your eyes is “too short” for the lens. The near point, for the person, is farther away from the normal near point (25 cm). Such a person has to keep a reading material much beyond 25 cm from the eye for comfortable reading. This defect can be corrected by using a convex lens of appropriate power.
3.
Hyphema –Bleeding in the front of
the eye, between the cornea and the iris. It blocks the vision completely or
partially. Hyphema is usually caused by trauma.
4. Presbyopia
– Presbyopia. This defect is called Presbyopia.
It arises due to the gradual weakening of the muscles and diminishing flexibility of the eye lens. In this case, a person may suffer from both myopia and hypermetropia. Such people often require bi-focal lenses. A common type of bi-focal lenses consists of both concave and convex lenses. The upper portion consists of a concave lens. It provides distant vision. The lower part is a convex lens. It provides near vision.
There
are other problems also like Optic neuritis, pterygium, retinitis, scotoma,
strabismus, stye, uveitis, and retinal detachment.
By: Shivani Awasthi (FullFry)
