Being the organ of vision, our eyes play a very important role in our life. Its the eyes that capture the images of all things around us and send them to our brain. This gives us the sense of sight, allowing us to see and interpret shapes & objects. When so crucial are our eyes for us, it is becomes our duty to take proper care of them. Regular eye test or eye examinations can help us to keep our eyes free of various diseases. It is always recommended that everyone, including children, must take up these eye test or eye examinations at least once in two years, if not annually.By knowing how our eyes work can help us better understand their importance.
How does the eye work?
- The eye works very similar to a camera
- Light rays pass through the lens and an image is formed on the retina
- This image is transmitted to the brain and triggers impulses so we can see
- The image needs to be formed correctly on the retina for us to see clearly
When you go for an eye test or eye examination, it is the health of cornea, and retina that is essentially checked. It is when there is some distortion in the passage of light to the retina that you are not able to see clearly. These distortions can be classifies as short sight or long sight. When you have short sight, it is the objects at distance that are unclear, and its vice versa when you have long sight. The shape of your eye plays a major role when it comes to the type of sight issues you have. For this, understanding the structure of our eye can help us to interpret these issues better.Structure and function of the Eye:
Outer covering of Eyeball: It consists of a relatively tough, white layer called the sclera. The sclera is covered by a thin, transparent membrane (conjunctiva), which runs to the edge of the cornea. The conjunctiva also covers the moist back surface of the eyelids and eyeballs.
Cornea: Light enters the eye through the cornea, the clear, curved layer in front of the iris and pupil. The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye.
Pupil: After passing through the cornea, light travels through the pupil (the black dot in the middle of the eye).
Iris: The circular, colored area of the eye that surrounds the pupil which controls the amount of light that enters the eye. The pupil dilates (enlarges) and constricts (shrinks) like the aperture of a camera lens as the amount of light in the immediate surroundings changes. The iris allows more light into the eye when the environment is dark and allows less light into the eye when the environment is bright.
Crystalline Lens: Behind the iris sits the lens. By changing its shape, the lens focuses light onto the retina. Through the action of small muscles (called the ciliary muscles), the lens becomes thicker to focus on nearby objects and thinner to focus on distant objects.
Retina: The retina contains the cells that sense light and the blood vessels that nourish them. The most sensitive part of the retina is a small area called the macula, which has millions of tightly packed photoreceptors (the type called cones). The high density of cones in the macula makes the visual image detailed, just as a high-resolution digital camera has more megapixels. Each photoreceptor is linked to a nerve fiber.
Optic Nerve: The nerve fibers from the photoreceptors are bundled together to form the optic nerve. The optic disk, the first part of the optic nerve, is at the back of the eye. The photoreceptors in the retina convert the image into electrical signals, which are carried to the brain by the optic nerve.