Types of contact lenses available

Silicone hydrogel contact lenses. These lightweight soft lenses allow more oxygen to penetrate the lens, making it easier for your eyes to breathe. Some varieties of silicone hydrogel lenses also have a moisture agent built in that keeps eyes fresh and moist, even in challenging conditions. If you travel a lot — or even if you just experience tired, dry eyes on a regular basis — talk to your ECP about switching to silicone hydrogel lenses.

There are several types of contact lenses available today:

Soft contact lenses. Most people who need corrective contact lenses are able to wear soft contacts. These lenses are made of a polymer-plastic material and water. The water allows oxygen to pass through the lens easily, which is healthier for the eye and makes the lenses more comfortable to wear — even for first-time users.

Two of the most popular types of soft lenses are daily disposable lenses and extended wear lenses. Daily disposables are worn for one day and then discarded. These are extremely easy to care for and don’t require additional soaking or rinsing.

Rigid gas permeable lenses (RGP lenses) are more durable than soft lenses, and can provide more clarity of vision. The newer versions of RGP lenses are made with silicone polymers, which aid in oxygen circulation through the lens to the cornea. Your eyes may take more time to adjust to RGP lenses because RGP lenses are not as flexible as soft lenses. Therefore, daily use is recommended.

Also unlike older versions of hard lenses, some RGP lenses are designed for extended wear, which means they can be worn overnight. Since sleeping in your lenses can reduce the amount of oxygen entering your eye (since your eyes are closed), it’s important to get regular check-ups from your eye doctor and follow all wearing and cleaning instructions for your extended wear RGP lenses.

High DK Lenses. The popularity of hyper-oxygen-transmissible lenses — also known as High DK or Extended Wear lenses — took off in the past few years. Now, technology has allowed lens manufacturers to create high DK lenses for daily and extended wear use that actually may reduce the risk of microbial keratitis, a bacterial infection on the cornea.
More oxygen passes through High DK lenses, which keeps both the lens and the cornea fresh and protected from bacterial build-up. In some cases, the extended wear lenses are preferred over corrective eye surgery, such as LASIK, since the risks of surgical complications are eliminated.

High Water Lenses. No, High Water Lenses are not contacts designed for use while you swim! Rather, these soft lenses are made with a high percentage of water. This water makes the passing of oxygen through the lens to the eye more effective, allowing the eye to “breathe.”

The soft contact lenses that were first manufactured were called “Low Water Content” soft lenses. They contain around 38% water. Modern soft lenses are now between 50% and 60% water. Some lenses are as much as 70% water, which means that only 30% of the lens is actually plastic!

Lenses that contain more than 65% water content are usually labeled “High Water Content.” “Mid Water” lenses are those that have between 50% and 65% water.

Silicone hydrogel lenses are super-permeable and a significant step above traditional soft lenses, which are made of hydrogel polymers. (The polymers are plastics containing water. Since plastic cannot carry oxygen through the lens, the water within it serves this purpose.)

Silicone hydrogel allows more oxygen to pass through the lenses to the cornea, making them safer and more comfortable for longer periods of wear. Those who want to sleep in their lenses and/or for whom corrective surgery is not an option can be ideal candidates for silicone hydrogel lenses, depending on the vision correction they need.

Cosmetic lenses or enhancers can correct your vision or just change your eye color or appearance. Some cosmetic lenses are cheaply produced and have an unnatural look to them — so be careful when you order them. Also, never order cosmetic lenses without an eye exam and professional fitting first. If they don’t fit you correctly, your eyes can dry out, leaving you vulnerable to a serious eye infection.

Soft contact lenses are made of plastic and water for ultra comfortable wear. They are available in daily, biweekly or monthly disposable configurations to suit a variety of needs. You can choose to have soft contact lenses that change your eye color (cosmetic lenses) for a change of pace, or you can opt for standard soft contact lenses. Regardless, you always need a valid prescription to purchase soft contact lenses.

For those who cannot wear the newly developed multifocal contact lenses, monovision lenses may be the perfect choice. Monovision (single vision) lenses work by correcting your dominant eye for distance and your non-dominant eye for near vision. Those who have tried monovision lenses find they can be easier to use than bifocal lenses, but some also experience a loss of depth perception. These lenses also don’t provide mid-range correction for such activities as computer use. This can be corrected using an intermediate-distance contact lens in place of the one for near vision as long as you don’t have trouble reading print that is close up.

For those who cannot wear the newly developed multifocal contact lenses, monovision lenses may be the perfect choice. Monovision (single vision) lenses work by correcting your dominant eye for distance and your non-dominant eye for near vision.

Those who have tried monovision lenses find they can be easier to use than bifocal lenses, but some also experience a loss of depth perception. These lenses also don’t provide mid-range correction for such activities as computer use. This can be corrected using an intermediate-distance contact lens in place of the one for near vision as long as you don’t have trouble reading print that is close up.

Sclera contact lenses are contact lenses that cover the entirety of the sclera, or the white of the eye. These types of contact lenses are often used in movies or theatrical performances thanks to their dramatic effects.

Photochromic contact lenses are contact lenses that respond to UV light to protect the eyes from UV damage. They work similarly to photochromic eyeglasses, which appear clear indoors and gradually darken when they become exposed to sunlight.

Polymethyl methacrylate lenses (PMMA lenses) were developed in the 1960s, and were the first ever prescribed to patients needing contact lens vision correction. These rigid lenses did not allow oxygen to pass through the durable plastic material to the cornea. Instead, when the wearer blinked, the lens would move, allowing the natural tears in the eye to transfer oxygen to the cornea. Since these lenses are not very comfortable, they are rarely prescribed to patients today.

Today, rigid gas permeable lenses (RGP) have replaced the PMMA lenses of the past. These durable contact lenses are much safer and more comfortable to wear, even for extended periods of time. For a more in-depth explanation, read on.

Frequent contact lens wearers generally know the difference between daily or monthly lenses or whether contact lenses are colored or not. There is another differentiator, and that is whether the contact lenses are soft lenses or hard lenses. This article will take a deep dive into hard contact lenses.

Conventional hard lenses were popular in the past. Known as PMMA, short for Poly (methyl methacrylate), they are not moldable to fit the eye as they are made of rigid plastic. Although they were durable and inexpensive, they also tend to be the least comfortable option for contact lens wearers, especially when first wearing them and the eye hasn’t adjusted to them. The lack of oxygen reaching the cornea may cause damage and be uncomfortable.

Alternatively, most hard lenses in the market today are rigid gas permeable (RGP) lenses made of materials that allow oxygen to reach the cornea while maintaining its shape on the eye. This reduces problems that may occur when the cornea does not get enough oxygen. They help slow the development of nearsightedness in contact lens wearers and correct refractive errors such as astigmatism with no distortion. Some RGP lenses are designed for extended wear (overnight). However, many eye specialists advise against wearing them for an extended period or while sleeping.

RGP contacts are incredibly durable, easy to care for, handle, and wear. They are more comfortable than PMMA lenses. However, RGP lenses cost more than PMMA hard lenses and are somewhat less durable. RGP lenses usually need to be replaced after 2 to 3 years of use. The RGP lenses can be quite economical compared to soft lenses, which require more frequent replacements.

The main disadvantages to hard lenses are their vulnerability to scratches. They can easily dislodge from the eye’s center position, and wearers may need to wear them consistently to grow accustomed to them.

If hard contact lenses are not as comfortable, you may be asking yourself, why do we still have them? Hard contact lenses may be required for specific prescriptions where soft lenses aren’t effective. These lenses can also be used to correct vision for people with unusually shaped or distorted corneas, such as astigmatism and keratoconus. 

Either way, it is always good to be well-informed on the types of lenses in case one may fit your needs. Make sure to always check with your eye care professional before purchasing your contact lenses.