Your life and eyes 5 min read

Understanding how the eye works

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Sight is considered to be the most important of your five senses. Despite this, many people are still yet to fully understand how the eye works and what can affect the health and condition of your eyes.

Your eyes may be small, but there are many different parts that work carefully together in order to create the picture you see in front of you.

With that in mind, we present a brief overview of how the eyes work and how different eye conditions or diseases can affect them.

How vision works

Your eyes rely heavily on light in order to create clear vision. Light enters through the pupil, and with help from the iris and cornea, the right amount of light is directed towards the lens of your eye.

The lens will bend, or refract, the light on to your retina. Your retina is made up of cells known as rods and cones, which work together to turn the image into electrical energy in order to send to the optic disk. It is then passed along the optic nerve and is processed by the brain. The brain does this in a matter of milliseconds.

Refractive errors can occur if your eyeball is an irregular shape, which results in light being refracted in the wrong place. This often results in blurry vision and means you will likely need to wear corrective lenses. For instance, myopia means that your eyes are slightly too long and the refracted light will focus just in front of the retina, instead of on it.

Similarly, if the curvature of your cornea or lens is not symmetrical, you may suffer with something known as astigmatism. When the light hits an irregularly-curved cornea, it is refracted more in one direction than another, which means the light won’t focus on the right part of the retina for clear vision.

Diagram of astigmatism

Anatomy of the eye

There are many different parts of your eye; each is as important as the next. You have probably heard of most of them. The iris of your eye is the coloured part of your eye and is responsible for regulating the amount of light that enters through the pupil.

The cornea of the eye is a transparent circular part at the front of your eyeball. It’s primary job is to refract the light, along with the lens. The lens makes up the transparent part behind your pupil, and refracts incoming light on to the retina.

The retina lines the inside of your eye, and is made up of light-sensitive cells known as rod and cones. Rods and cones are crucial for seeing in low light and colour perception. Rod cells in particular will remain sensitive even in low light and are crucial for seeing in twilight and night conditions.

Forest in twilight

Cone cells are important for your colour vision. There are 3 different types of cone cells, each reacting to different size wavelengths to detect blue light, green light and red light.

Another key part of your eye’s anatomy is the macula. This is a yellow spot on the retina at the back of your eye, and it works together with something known as the fovea. The fovea creates an indentation at the centre of the macula and is the home of the greatest concentration of cone cells. The part of the image that is focused on the fovea is the image most accurately recognised by your brain.

An eye condition known as age-related macular degeneration can affect your macula, resulting in its deterioration. There are two types of age-related macular degeneration; dry AMD and wet AMD. Dry AMD can occur when the macula’s cells become damaged by yellow deposits. Wet AMD occurs when abnormally-formed blood vessels grow under the macula, and is much more serious. AMD symptoms include the blurring of your central vision, as well as colours appearing less vibrant.

Discover more eye conditions that can affect your vision, how to identify them and how to treat them here.