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How Do Contact Lenses Work?

Guides & How To

structure image How Do Contact Lenses Work?


Contact lenses are a great alternative to eyeglasses for many people. They’re more compact since they sit directly on your eyes, and they make it easier to play sports and participate in numerous other activities. When you wear contacts, you don’t have to worry about your glasses slipping, pinching, breaking, or getting in your way.

But have you ever wondered how contact lenses work? How something so small can correct your vision in such a precise way? If so, read on for a review of the different types of lenses that are out there and a look at how contacts work.

How Do Contacts Work?

When it comes to correcting vision, contact lenses work basically the same way as eyeglasses: They bend light so it is focused on the retina. The retina is the light-sensitive structure at the back of the eye. In order to have a clear image for the brain to process, light must focus directly on the retina.

If you’re nearsighted, light comes to a focus in front of the retina. And if you’re farsighted, light comes to a focus behind the retina. In cases of both nearsightedness and farsightedness, objects appear blurry due to this improper focusing of light.

Contact lenses work by bending light in a way that focuses it directly on the retina. This creates a clear image and gives you a crisp view of the world around you.

What Is a Contact Lens Prescription?

Your contact lens prescription is determined based on the findings of your contact lens exam and fitting. This exam is typically separate from your annual comprehensive eye exam and often has an added cost.

While it may seem similar to a glasses prescription, your contact lens prescription includes different information and measurements, and the two cannot be used interchangeably.

Look for the following elements in your contact lens Rx:

  • Lens brand and material – The specific contact lens type that your doctor has determined is best suited to your eyes during your exam and fitting.
  • Power/Sphere (PWR/SPH) – The lens power or strength (in diopters) needed to correct your refractive error. If the number has a minus sign (-), you are nearsighted. If it has a plus sign (+), you are farsighted.

  • Base curve (BC) – The curvature of the contact’s back surface.
  • Diameter (DIA) – The size of the contact lens from edge to edge.
  • Cylinder (CYL) ) – The measurement that indicates the amount of correction of astigmatism.
  • Axis) – This indicates the orientation of the cylinder correction.
  • Addition (ADD) ) – The amount of added plus power you need to see clearly up close. It is most common in prescriptions for people with presbyopia.
  • Issue date and expiration date) – Contact lens prescriptions are typically valid for one to two years.

A contact prescription may also include:

  • Recommended solution or lens care system
  • Replacement schedule

One thing to note about vision prescriptions is that correction needs for each eye can be different. As long as your contacts or glasses help you see more clearly and comfortably, it’s okay if the numbers for your left eye don’t match the numbers for your right eye.

Why Are Contacts and Glasses Prescriptions Different?

Contacts are measured and prescribed differently than glasses because, unlike glasses, contact lenses sit right on top of your eye. This means the surface area of the lens is much smaller and the curve of your eyeball must be taken into account. This also allows contact lenses to be much thinner than eyeglass lenses.

Another difference between eyeglass and contact lens prescriptions? The brand and type of your contacts is actually part of your prescription. Your eye doctor determines the best brand and lens type during your contact lens exam and fitting.

They may even give you a sample pack of lenses to try before finalizing your prescription to ensure you feel comfortable and can see clearly in your new contacts.

Types of Contact Lenses

There are several types of contact lenses on the market, each designed to correct specific vision problems. Most disposable contacts are available on daily, weekly, or monthly replacement schedules.

  • Single-vision contact lenses correct vision at a single distance, like for myopia or hyperopia.
  • Bifocal and multifocal lenses contain two or more prescription strengths to provide clear vision at both distance and near. They are typically prescribed when a person has presbyopia.
  • Spherical lenses are designed to correct nearsightedness and farsightedness.
  • Toric lenses are soft contacts specially designed to correct astigmatism in addition to nearsightedness and farsightedness.
  • Colored contact lenses are a great option if you’re interested in exploring different iris hues.

Additionally, numerous types of contact lenses have been developed to help minimize dry eye symptoms associated with contact use. Be sure to speak with your eye doctor about the best fit for your needs and desires during your next contact lens consultation.

Is it time for your annual eye exam? Call your eye doctor and schedule an appointment to keep your eye health in check — and to learn which contact lenses will work best for you.