13.7. What is inside Our Eyes?

We see things only when light coming from them enters our eyes. Eye is one of our most important sense organs. It is, therefore, important to understand its structure and working.

To see an object, light must enter our eyes. This light can come directly from the object or can be reflected light. Without light, our eyes cannot perceive any shapes or colors, making it impossible for us to see anything.

Imagine trying to find your way in a dark room. Without light, you won't be able to see anything, which shows just how important light is for vision.

The eye has a roughly spherical shape. The outer coat of the eye is white. It is tough so that it can protect the interior of the eye from accidents. Its transparent front part is called cornea.

The eye is shaped somewhat like a ball and is designed to protect its inner structures. The outer white layer protects the eye, while the transparent part, known as the cornea, allows light to enter the eye safely.

Think of the eye as a camera. The tough outer layer is like the casing of the camera, protecting the internal components, and the cornea acts like the lens that focuses light into the camera.

Behind the pupil of the eye is a lens which is thicker in the centre. Behind the cornea, we find a dark muscular structure called iris. In the iris, there is a small opening called the pupil. The size of the pupil is controlled by the iris.

The iris is the colored part of the eye and has muscles that adjust the size of the pupil. The pupil is the opening that allows light to enter the eye, and its size changes depending on the brightness of the surroundings. In dim light, the pupil expands to let in more light, while in bright light, it constricts to limit light entry.

Consider the iris and pupil as a camera's shutter. The iris opens and closes to let the right amount of light in, just like a camera's shutter does when taking a picture.

The lens focuses light on the back of the eye, on a layer called retina. The retina contains several nerve cells. Sensations felt by the nerve cells are then transmitted to the brain through the optic nerve.

The lens is a crucial part of the eye that helps to focus light onto the retina at the back of the eye. The retina converts light into electrical signals that the brain can understand, which is essential for the process of seeing.

Think of the lens as a projector lens. Just as a projector lens focuses light to create an image on a screen, the lens of our eye works to focus light onto the retina, allowing us to see.

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 blind spot is an area in our vision where we cannot see because there are no light-detecting cells where the optic nerve meets the retina. Although we have this blind spot, our brain fills in the missing information based on surrounding images.

It's like a video game where there's a glitch in one area of the game screen that prevents you from seeing what's happening there. Your mind compensates by making assumptions about what’s in that area based on what it can see.

Nature has provided eyes with eyelids to prevent any object from entering the eye. Eyelids also shut out light when not required.

Eyelids serve as a protective barrier for our eyes. They close to protect the eyes from dust and injury, and they also help regulate the amount of light entering the eyes, contributing to overall eye health.

Think of eyelids as window shutters. Just as shutters can be closed to protect windows from the weather and regulate light, eyelids do the same for our eyes.

Some persons can see objects close to them clearly but cannot see distant objects so clearly. On the other hand, some persons cannot see objects nearby clearly but they can see distant objects quite well.

These issues relate to refractive errors in the eye, such as myopia (nearsightedness) and hyperopia (farsightedness). These conditions can often be corrected with glasses or contact lenses.

Imagine trying to focus a camera. If the lens is misaligned, you might only see a clear image of objects that are very near or very far away, just like someone with vision problems.

Sometimes, particularly in old age, eyesight becomes foggy. It is due to the eye lens becoming cloudy. When it happens, persons are said to have cataract.

Cataracts occur when the lens of the eye becomes cloudy, leading to blurry or foggy vision. This condition can be treated surgically by replacing the cloudy lens with a clear artificial lens.

It’s similar to looking through a dirty window. When the window is clean, you can see clearly, but when it’s dirty, your view becomes obscured. Surgery helps to restore that clear vision.

--