How do contact lenses work?

Introduction to contact lenses

If your vision is less than 20/20, you're lucky to live in a time when you have so many options to correct your eyesight. Contact lenses, which have only been in widespread use for the last 60 years or so, have changed the lives of millions of people. With contacts, you can see clearly even in the rain, you don't have to worry about fogging up your glasses, and you can play sports without hindrance.

But how do contact lenses work? The answer is fascinating, so keep reading to learn more about what's happening when you pop in your contacts for a day of clear vision.

How contact lenses correct vision

If you have 20/20 vision, your eye focuses light exactly onto your retina, the structure at the back of your eye. Whether you're nearsighted or farsighted, your vision is unfocused because your eye is focusing light in the wrong place within your eye. Contact lenses (just like prescription eyeglasses) adjust the direction of light, so it hits your retina exactly right — and that corrects your vision.

When you wear a contact lens, it rests on the tear fluid that covers your eyes. That makes it easy for each contact to move as your eyes move, so you have perfect vision in every direction. Unlike eyeglasses, contact lenses allow perfect peripheral vision, as well as central vision.

Refractive errors and vision correction

Your contact lenses can correct several types of refractive errors within your eye. The most common ones include:

• Myopia: Commonly called nearsightedness, myopia occurs when light focuses in front of your retina, instead of on it. Your near vision might be fine, but objects in the distance are blurry. Single-focus or multifocal contact lenses can correct this.
• Hyperopia: Farsightedness is pretty much the opposite of nearsightedness. Because light focuses behind your retina, you have good distance vision, but you have blurry vision for things that are nearby. Contact lenses correct the focal point, so light hits the retina and you see everything clearly.
• Astigmatism: This occurs when the surface of your cornea is uneven or irregular, and it typically co-occurs with either myopia or hyperopia. While many people with astigmatism opt for hard contact lenses, toric contact lenses, which are weighted soft lenses designed to correct astigmatism, can also be useful.
• Presbyopia: This condition occurs with age, as the lens of your eye becomes more rigid. It's the reason older people start wearing reading glasses, since their near vision isn't as flexible. Multifocal contact lenses can help with this condition.

Lens prescription and fitting

If you've worn eyeglasses before, you're familiar with the basic eye exam you get from your eye care professional. A contact lens fitting goes far beyond that, and it's necessary before you can get a prescription for contacts. 

At a contact lens exam, your eye care professional measures the curvature of your eye and the size of your pupil to determine the size of contact lens you need. Specific measurements include base curve, diameter, power, and (if you have an astigmatism) axis. They also evaluate the tear film covering your eye to make sure your eyes are moist enough to wear contacts well. Your eye care professional will also have you try on some sample contacts to see how they feel and make sure the fit is right.

If you're a new contact lens wearer, you'll probably get to wear a trial pair for a week or so. After that, your eye care professional will give you a prescription to buy a larger supply of contacts. You’ll need to keep this prescription since you can’t purchase contacts (in the United States) without it.

How contact lenses interact with the eye

Contacts sit directly on the tear fluid covering your eye and move as your eye moves. Your eyelids give them protection, so they don't fog up like glasses, which feels like such a gift on rainy days.

Oxygen and moisture permeability

The higher the water content of a pair of contacts, the more oxygen can flow through the contacts into the eye. That moisture and oxygen combine to provide comfort to the wearer. But different brands of contacts contain different levels of water content. That's because people's eyes vary. One person might need a high water content lens for comfort, while another might find that those lenses actually draw moisture out of their eyes. Your eye care professional can help you determine which brands and water content levels work best for you.

Tear film and lubrication

The stability of the tear film covering your eye makes a big difference to how your contact lens feels — and wearing contacts can alter that layer of tear film. If you're naturally prone to dry eye, your tear film is inherently unstable, which contributes to the discomfort you may sometimes experience wearing contacts.

Your eye care professional can run some measurements of your tear film stability to help correct any problems. You may need to lubricate your eyes more frequently with contact lens solution or artificial tears, or your eye care professional may recommend a different type of contact lens to solve the issue.

Benefits and considerations of contact lenses

Contact lenses provide clear benefits to many people needing vision correction, although you have to make sure you're practicing good hygiene and eye care.

Visual clarity and field of view

When you wear eyeglasses, those frames are always in your field of view. They block part of your vision, and, of course, your vision is completely uncorrected outside the edges of the frames. Contacts, on the other hand, provide an uninterrupted field of view with no obstructions. Your peripheral vision is as clear as your central vision. In addition, contacts do away with any vision glitches stemming from reflections on your lens, distortions if the lens wasn't ground correctly, or smudges because of dirt building up on the glasses lens.

Convenience and Lifestyle

What's better than going snorkeling or scuba diving without having to cough up the money for a prescription mask or going for a run without having a pair of glasses bouncing on your nose? Or joining your softball team for this week's game, confident that you'll have clear peripheral vision, so you can keep your eye on the ball? (Pun intended.)

Contact lenses are ideal for your active, sports-loving lifestyle. They also let you put your best face forward, both on a daily basis and for special occasions. Think about all those photos where you'll be able to see your eyes without reflections from glasses marring them. 

But if you're going to wear contacts, you have to pay attention to hygiene. Depending on the type of contacts your eye care professional prescribes, you may need to clean them regularly. You also need to practice good hygiene when putting your lenses in and taking them out, and you have to follow the prescribed wearing schedules to protect your eyes.

Making your contact lenses work for you

Your contact lenses can give you the clear vision you want while helping you look great and giving you more freedom in your daily life. Make sure you see an eye care professional who can fit your lenses properly and help you choose the right type of contacts, so your experience can be as comfortable and healthy as possible. Call us today, so we can help you get the exact brand of contacts your doctor prescribed.

FAQs

Are contact lenses suitable for everyone?

While most people can wear contacts successfully, some people may have eye conditions that prevent it. Your eye care professional can help you determine whether contacts are the right choice for you.

Can I sleep with contact lenses?

Generally, no. Definitely no. If you wear extended-wear soft contacts, you may be able to sleep with them. Even then, it’s probably not a good idea to do it every night. Be sure to avoid dry eye and practice good hygiene.

Can contact lenses be worn while using digital devices?

Absolutely, although some people find that they develop issues with dry eye or eye strain while working for long periods at a computer screen. You may want bifocal contact lenses or special contact lenses designed to protect your eyes against blue light and glare.

What can you tell me about the history of contact lenses?

So, so much. We wrote a whole blog post about it and how cool Leonardo DaVinci was.