Understanding How the Human Eye Works

The eyes are one of the five common senses and allow us to see everything that surrounds us. But how does the eye work, and why are some people short-sighted and others long-sighted? To understand that, we first have to know the different parts of the eye.

• Cornea- This is the dome-shaped front layer of the eye.
• Iris- The muscle that controls how much light enters the eye and the size of the pupil. This is also the part that gives your eye color like brown or blue.
• Pupil- The small black dot in the middle of the eye where the light enters the eye.
• Lens- Found behind the pupil and iris, it helps focus light on the eye.
• Retina- It changes the light into electrical signals and if found at the back of your eye.

How We See

This is when we see things as they are, which happens in people who do not have any eye problems. For normal vision;

Light rays enter your eye via the cornea, which is the transparent ‘window’ of your eye. Its refractive nature bends the light such that it passes freely via the pupil in the center of the iris.

The iris works by controlling how much light enters the eye. It shrinks when there is too much light and enlarges when there is too little.

After the light rays enter the eye, they pass via the clear, flexible lens, which lengthens or shortens its width to focus the light properly. The light then passes through a transparent, dense, gel-like substance, the vitreous, before reaching the retina.

The retina functions a lot like a camera film because it captures all the light rays that come into the eye and, through millions of nerve endings, processes that light into light impulses and sends them to the optic nerve, which then sends them to the brain.

Those millions of nerves present in the retina are divided into cones and rods. Cones help us see color and produce the images in fine detail, while the rods are used in the perception of dark and light, including the shades of gray.

In the retina, the image is also inverted into an upright position because it originally enters the eye in an upside-down position.

Short-Sightedness / Myopia

This is a condition where the affected people are only able to see things that are close to them. This happens when the eye is too long.

Unlike in normal vision, where the light rays focus at the back of the retina, they focus only on the front part, which makes distant objects look blurry.

Long Sightedness / Hypermetropia

Long-sightedness is when the patient is only able to see things that are far away. It also happens when the light from close objects is not brought into focus on time to properly hit the retina.

Unlike in myopia, where the light is focused in front of the retina, in long-sightedness, the point of focus would be behind the retina.

The lens, in a process called accommodation, tries to adjust its thickness by becoming more rounded and fat to try and bring the light rays in focus on the right part of the retina.

However, people with hypermetropia are not able to fully accommodate, which results in the light rays becoming blurry. That may happen because;

• Your eyeball is very short.
• Your cornea is very flat.
• Your lens is unable to properly focus the light.

We should always take care of our eyes because the slightest injury may affect how light enters into the eye and how it is focused on the retina. Learn about common eye problems.

While short and long sight is mainly hereditary, it is key that you take proper care of your eyes and make regular appointments with your doctor. To deal with those problems, you can get glasses, get medication, or, if possible, get surgery.