Contact lenses have been around since 1887, when they were made of glass. Luckily, contact lenses have evolved a lot since then. Modern lenses are safer, more comfortable, and better at correcting a variety of vision challenges.
Today, contact lenses can be made from different materials, and which ones are best for the wearer depends upon the vision challenges to be corrected. This post focuses on what patients considering contacts for the first time need to know.
1. Contact Lens Composition
Contact lenses of all types sit directly on the corneas, which need oxygen to stay healthy. However, as no blood flows to them, corneas must get their oxygen passively from the air. Contact lenses can be soft, gas permeable, rigid gas permeable, or hybrid in their construction—each is made of different materials and with different ways of ensuring that corneas receive enough oxygen.
These tend to be the most comfortable, are made of hydrogel, which is a type of flexible plastic that holds water. The softness of these lenses depends upon how much water they hold. Thinner lenses hold less water than thicker ones. Your corneas receive their oxygen from the water.
Gas permeable lenses
Whether rigid or not, gas permeable lenses are made of fluorosilicone/acrylate, which holds little water but has microscopic pores through which oxygen can reach corneas. Gas permeable lenses are rated by how much oxygen they allow to the cornea. These lenses are more rigid than soft lenses, making them great for those with astigmatism, or misshapen corneas. Their rigidity also provides for sharper vision than soft lenses.
As their name implies, hybrid lenses are made of a combination of soft and gas permeable materials. Generally, the center of these lenses is rigid while the surrounding ring is soft.
2. Cost of Contact Lenses
The cost of contact lenses depends on what kind they are, their disposal frequency, and other factors. Conventional soft lenses that last for a year are typically the least expensive with costs ranging up to $200, while hybrid lenses can cost up to $2,000 for a year. Daily disposable lenses may cost up to $760 per year, while monthly disposable lenses cost about half that much.
These prices will be much higher for contact lenses that are tinted to change eye color appearance or give eyes a special effect, like making the cornea look like a flower, star, or lizard eye—yes these are all possibilities! They may also be higher for bifocal and multifocal lenses.
Although wearers may be tempted to save a little money by shopping for lenses online, be aware that shipping times can be longer than it takes to get lenses through a local optometrist, especially if mistakes with your prescription happen.
Regardless of where lenses are obtained, they should only be worn for as long as prescribed. Wearing them longer than they are designed to be worn is a risky way to try to save money and will lead to eye infections.
3. How to Read Contact Lens Prescriptions
Prescriptions for contact lenses can have up to eight different measurements, specifying refraction power, base curve, diameter, cylinder, axis, add power, color, and brand.
Refraction power refers to the level of correction needed. Higher numbers mean more correction than lower. Also, negative numbers indicate myopia, or nearsighted correction, while positive numbers indicate hyperopia, or farsighted correction.
The next two measurements are specific to fit the lens to the cornea. Base curve is a measurement of the curvature needed to fit the cornea. Higher numbers mean a flatter curvature. Diameter is the measure of the width of the lens to cover the cornea. Lenses with a diameter that is too long or too short will lead to eye irritation.
If toric lenses (more on those in a moment) are prescribed for astigmatism, the prescription will include a measurement for cylinder, which refers to the astigmatism severity. Prescriptions for astigmatism will also have an axis measurement, indicating orientation of cylinder power.
Wearers who need extra magnification for reading can now get bifocal or multifocal lenses. Their prescriptions will list measurements for add power, which is the power of magnification needed in specific areas of the lens. If wearers want lenses that give their eyes a special effect or color, that will also be specified.
If this information sounds complicated, it’s because the human eye is a very complex organ. Always talk with your eye care professional about the technicalities of your corrective lens prescription. And for a deeper dive into contact lenses, you may want to check out our video library.
More on Prescriptions
By law, every contact lens prescription must also include a brand specification. Be aware that an individual’s prescription for contact lenses differs in magnification from their prescription for eyeglasses. In other words, these prescriptions are not interchangeable. It is recommended that contact wearers also get their eyeglass prescription updated annually so they can have glasses as a backup when taking a break from contact lenses.
4. What are Toric Contact Lenses?
When astigmatism is more severe, causing focus issues both horizontally and vertically, toric contact lenses may be prescribed. These lenses can be soft or rigid gas permeable. Toric lenses are designed to correct both vertical and horizontal vision challenges.
To be effective, these highly customized, precision lenses must sit on the cornea in a specific position and not rotate at all like other contact lenses. To prevent such rotation, toric lenses are weighted along their bottom edge.
Toric lenses tend to be more expensive than other lenses because fitting them for perfect alignment to fix astigmatism can be difficult and may require the trying of more brands and pairs than other lenses.
5. How do Multifocal Contact Lenses Work?
Usually, around the age of 40, adults develop presbyopia, which means their eyes begin losing the ability to focus on close up things. They begin to need reading glasses.
Contact lenses, like eyeglasses, can be bifocal or even trifocal. As in eyeglasses, these kinds of contact lenses, called segmented, have different zones of vision correction with regular correction at the top of the lens and reading correction at the bottom. So that these lenses don’t rotate around the cornea, moving the zones, the bottom edge of the contact lens is flat.
Multifocal lenses also come in designs providing simultaneous vision. Rather than having sharply delineated segments of different magnification, simultaneous vision lenses can either have alternating rings of different magnification or a central sphere of distance magnification surrounded by a graduated ring of differing magnification powers.
6. What do Contact Lens Expiration Dates Mean?
All contact lenses have expiration dates. Lenses come sealed in saline solution. The expiration date, which is generally four years from packaging date, actually refers to the time at which the seal on the individual contact lens containers could fail.
If that seal fails, bacteria could contaminate the lens, leading to eye infections if worn. It is not that the lens itself will deteriorate after the expiration date, but rather that it could become compromised after that date. Contact lens wearers should never wear lenses that have expired. The risks are not worth it.
Expired, and indeed all used, contact lenses should be thrown in the trash. Lenses should never be washed down a sink or flushed down a toilet because wastewater treatment facilities can’t always prevent lenses from slipping through into freshwater streams, where they can harm aquatic animals, who mistake them for food.
Need Help Transitioning to Contacts from Glasses? Call Campus Eye Center!
With convenient locations in Lancaster and Willow Street, PA, Campus Eye Center is recognized as one of the best resources for helping patients live better by seeing better. If you’re looking to try contact lenses for the first time, or you simply need an updated prescription, get in touch for an appointment with our friendly eye care team today!