Contact Lenses: Why One Type And Size Doesn't Fit All
Contact lenses have existed for over 100 years but it wasn't until the 1940s that they became a popular method of vision correction. Initially, the lenses were a thin glass that did not allow oxygen to pass through to the eye. This meant they could only be worn briefly before a wearer's corneas swelled. Today, contact lenses are safe, comfortable, and used to treat many different vision and eye health problems. Eye care technology, including contact lenses, evolves daily. If you have been told in the past that you were not a good candidate for contact lenses, your answer would be different today!
What Are Contact Lenses?
Contact lenses are thin, plastic lenses shaped like small bowls that sit on the cornea (the eye's front surface) to correct vision problems. In contrast, glasses sit at a slight distance away from the eyes. When placed in the eyes correctly, contact lenses make your vision clearer without being noticeable to other people.
How Do Contacts Work?
When used for vision correction, contact lenses refract light as it enters the eye, allowing the light to focus correctly on the retina for clear, sharp images. Glasses function similarly—both lenses correct refractive errors in the eye that prevent light from focusing correctly. Contacts adhere to the tear film, a layer of fluid on your eye that keeps it moist and protected, keeping them in place. This gentle adhesion lets them move naturally with your eye, ensuring they don't shift when you blink.
The Different Types of Contact Lenses
The type of contact lens your eye doctor prescribes will depend on your visual and medical needs. What may work for one person may not work for another.
Soft Contact Lenses
Soft contact lenses are thin and flexible, allowing them to fit the shape of your eye easily. After years of innovation, soft lenses were introduced in the U.S. in the 1970s and have since dominated the contact lens market, with 90% of wearers choosing soft lenses. Soft contacts are great at retaining moisture and letting oxygen through the eye, making them the most comfortable option.
Rigid Gas Permeable (RGP) Contact Lenses
Rigid gas-permeable contacts are "hard" contact lenses, meaning they don't bend and flex like soft ones. Despite their rigid structure, they let oxygen through so your eyes can breathe. RGP lenses provide sharper vision correction for some patients; however, they take time to get used to. When compared to soft lenses, many patients find them less comfortable. Rigid gas-permeable contacts extend over a broader portion of the eye to cover the sclera (the white part of your eye). They can help correct vision issues caused by corneal abnormalities.
Scleral Contact Lenses
Scleral lenses are more complex than soft and hard contacts, requiring additional time and expertise for proper fitting. Many eye doctors do not fit them because of the complexity. However, scleral lenses can be life-changing for patients with diseased corneas. Each lens is custom-fit for each eye, making them more expensive than other lenses on the market.
Hybrid Contact Lenses
Hybrid contacts combine the advantages of soft lenses and RGPs: they have a rigid zone in the center and a soft outer "skirt" of material surrounding it. This design offers the clear vision of RGP lenses while maintaining the comfort of soft lenses. Like scleral lenses, hybrid contact lenses require precise fitting and cost more than other contact lenses, making them less commonly used.
Single-Vision Contacts
Single-vision contacts correct refractive errors such as nearsightedness, farsightedness, and astigmatism. They have a single "power" of vision correction, enhancing clarity for one specific vision need. This power is indicated in the sphere (SPH) column of your contact lens prescription as a positive or negative number of diopters, indicating the strength of your prescription.
Contact Lenses for Astigmatism (Toric Lenses)
Toric contact lenses address the irregular curvature of corneas that occur with astigmatism. They also simultaneously correct for other refractive errors like nearsightedness and farsightedness. Unlike typical contact lenses, toric lenses are shaped like a donut slice rather than a sphere and have a "correct" orientation on the eye's surface. They shouldn't rotate in different directions. They also have a cylindrical power component, measured in diopters, and a spherical power component. If you wear toric contacts, you'll see numbers in the "SPH," "CYL," and "Axis" columns on your prescription. Toric lenses need this additional measurement to account for the cornea's irregular shape caused by astigmatism—its uneven curve merits a slightly more complex prescription.
Multifocal Contacts
Multifocal contacts are great for people who wear progressive or bifocal glasses for presbyopia. They provide clear vision at various distances, whether far, intermediate, or near. They are also great for someone who needs help seeing up close but does not want to wear glasses. With these lenses, patients typically have to come back to the office for fine-tuning, as the fit can be more complicated.
Colored Contacts
While most contacts are clear and hard to notice, colored contacts' purpose is to enhance or alter eye color. Colored contacts can be subtle, bold, used to correct your vision, or purely for aesthetic purposes. It's important to note that they still require a fitting and prescription! These lenses do not come in multifocal or with astigmatism correction unless you order costly, custom-made lenses.
Orthokeratology (Ortho-K)
Orthokeratology is a treatment that involves wearing rigid gas-permeable contacts overnight while you sleep. While sleeping, the contacts reshape your cornea to counteract the effects of myopia and astigmatism. The effects are temporary, requiring nightly wear to maintain clear vision throughout the day. With Ortho-K lenses, patients will be free of glasses and contact throughout the day. These lenses can also be used to slow the eye's growth and help decrease how nearsighted a patient may have become.
How Do You Get a Contact Lens Prescription?
Contacts require a separate prescription from glasses. To get a contact lens prescription, you first need to schedule an eye exam and let the office know you are interested in wearing contact lenses when you book the appointment. Your eye doctor will include a contact lens exam and fitting during your appointment to see what type of contacts will best suit your eyes.
The fitting process and cost for contact lenses varies for each kind of lens and its fit complexity. Single-vision soft lenses are the easiest to fit, making the fitting fee minimal. On the other hand, scleral and hybrid lenses are the most complicated, can take more than one visit, and are more expensive.
No matter what type of contact lens you get for you, the fit should be comfortable, you should be able to see clearly, and your eyes should be happy.
