Through the Lens: Decoding the Wonders of Contact Lenses and Glasses

Written By: Jessica Liao

Do you ever wonder how a piece of glass or plastic could magically improve your vision? For those of you who experience blurry vision and have been wearing glasses for the majority of your life, this article is for you. An increasing number of people are starting to wear glasses or contacts due to the development of technology, especially when nowadays, children are introduced with a mobile device at a young age. But what causes our vision to become blurry?

What are contact lenses?

First invented in 1888 by Fick and Edouard Kalt, contact lenses provide the same function as glasses, but instead of wearing a frame consisting of two lenses in front of your eyes, the lenses sit inside your eyes to improve your vision. When they were first invented, contacts were made out of hard plastic that could not absorb water; however, it was uncomfortable because it was non-permeable, meaning that it didn’t allow any oxygen to pass through the lens of the eye, therefore, contact lenses today, are made of soft plastic, similar to gel, which is more flexible, easy to wear, absorb water, and permeable.

Why do we need contact lenses?

A growing number of individuals require glasses or contact lenses due to the misshapen lens in their eye, which changes the focal length of the light waves entering the eye, making their view blurry. This could be caused by multiple factors such as prolonged reading, excessive use of digital devices, lack of exposure to natural sunlight, genetics or age.

With normal vision, the light rays are bent or refracted as they enter the eye and they are brought to focus on the retina which is located at the back of the eye. The light ray

s first pass through the cornea and then the crystalline lens where they both contribute in bending the light rays directly on the retina. The cornea is a transparent layer that covers the pupil and t

he iris, and the crystalline lens is part of the accommodative system so it adapts to viewing distances to provide a clear image by adjusting its shape and curvature.

Short-sightedness (myopia)

This is when you are unable to see distant objects clearly

• The distance between the lens and the retina is too far (eyeball being elongated)

• Light is focused before it reaches the retina (lens being too thick and curved)

• Corrected by using a concave or diverging lens

• Diverges light rays before entering the eye

Far-sightedness (hyperopia)

This is when you are unable to see objects in close proximity

• The distance between the lens and retina is too small (eyeball being too short)

• Light is focused behind the retina (loss of elasticity of lens, often age related)

• Corrected by using a convex or converging lens

• Converges light rays before entering the eye

How do contacts work?

A layer of tear film spreads over the eye when you blink making it smooth and clear to keep the eyes moist. Contact lenses are placed directly in your eye where it floats on the tear film that covers the cornea.

The tear film is made up of three layers:

1. Oily layer on the outside

2. Watery layer in the middle

3. Inner mucus layer

Glasses are the same except you wear them with a certain distance between the eye and the lenses. Therefore, the focusing power could be different when using glasses instead of contact lenses.

Concave lenses are thicker at the edges and thinner at the center so light is bent towards the top and bottom of the lens or outwards. By using a concave lens, it reduces the refraction of light and increases the focal length so that the light is focused on the retina, since in short-sightedness the distance between the lens and retina is too far.

Convex lenses are thinner at the edges and thicker at the center so light is refracted more towards the center. By using a convex lens, it increases the refraction to decrease the focal length so that the light is focused on the retina, since in far-sightedness the distance between the lens and retina is too short.

Which one is better?

There isn’t a specific answer to this question since it all comes down to the user's personal preference; however, contact lenses and glasses both have their different strengths and weaknesses.

Contact lenses

Advantages

Disadvantages

Because it sits directly on the eye, it moves with your eye as you look around unlike glasses, avoiding a prismatic effect that can often cause motion sickness Gets protection from your eyelids so it doesn’t get wet or foggy Smaller and thinner than glasses Gives you freedom of not having to wear something on your face (suitable for playing sports) Allows you to wear non-prescription sunglasses easily

Higher risk for eye complications and infection, therefore you have to clean and disinfect them properly It could be a challenge to get used to at the beginning especially when learning how to take them on and off

glasses

Advantages	Disadvantages
Able to easily take them on and off Could be stylish to some individuals since users are able to customize lenses and frames to their liking Allows the use of bifocals (two lenses), trifocals (three lenses) and progressives (no line bifocals or trifocals)	Uncomfortable when wearing them for a long time Since the glasses sits a certain distance away from your eyes, peripheral vision may be an issue

Conclusion

Although glasses and contacts are so common and regularly utilized by people, there still remains a general lack of understanding regarding the functioning of glasses and contact lenses, therefore understanding the science behind glasses and contact lenses can shed light on how these seemingly ordinary pieces of glass or plastic can improve our vision. Moreover, as technology advances and the prevalence of digital devices increases, more people are relying on these vision aids, so it is useful to get a deeper understanding of the inner workings of these vision correcting devices.