Sara Butterworth, O.D.
Christine Sindt, O.D.
Peer Review Status: Internally Reviewed
Creation Date: March 2002
Last Revision Date: April 2002

1. Why can't I use my glasses prescription to get contact lenses?
2. What is Computer Vision Syndrome and what can I do about it?
3. I have always wanted to change my eye color. What are my options with contact lenses?
4. I have astigmatism. What exactly is that and can I wear contact lenses?
5. How would I know if I have an eye infection or a corneal ulcer?
6. I wear bifocals or reading glasses - can I still wear contact lenses?
7. What is the best soft bifocal contact lens available on the market?
8. What are the advantages and disadvantages of soft contact lenses compared to RGP's (Rigid gas permeable lenses)?
9. I have diabetes. Can I still be a successful contact lens patient?

Why can't I use my glasses prescription to get contact lenses?

There are a number of reasons why the glasses prescription cannot be used for contact lenses. Contact lenses classified by the FDA as a medical device and are therefore regulated differently than glasses. Because you are actually putting a contact lens on the surface of the eye, there are risks for infections, ulcers, and other complications that are not present with glasses.

When contact lenses are fitted to the eye, much more is taken into account than just the numbers from the glasses prescription. The curvature of the cornea (the clear tissue at the front of the eye that the contact lens sits on) is one important measurement that is taken. The diameter of the contact lens with respect to the diameter of the cornea is looked at as well. Position of the eyelids can affect contact lens choice. Additionally, health of the surface of the eye and the surrounding lids is taken into account.

People often notice that the contact lens prescription differs from the glasses prescription in the numbers. This is because glasses sit about 12 mm from the eye, and contact lenses sit right on the eye. In order to account for this distance between the glasses and the eye, a mathematical calculation is made to determine the appropriate contact lens power.

What is Computer Vision Syndrome and what can I do about it?

I have always wanted to change my eye color. What are my options with contact lenses?

There are an increasing number of options to change or enhance your eye color with contact lenses. There are two broad categories of lenses: those that have sheer or transparent tints and those that have opaque tints.

Individuals with light colored eyes can wear either type. Individuals with dark colored eyes generally see more dramatic effects with opaque lenses that actually cover their natural eye color.

The exciting thing about colored contact lenses is that you don't have to even need visual correction to wear these lenses! You can have great eyesight and still be fit with lenses. It is important to remember, though, that contact lenses are a medical device. Because of this, the fitting process for colored contact lenses is the same as non-tinted lenses. Measurements must be taken of the eye in order to determine the proper fit. Assessment of the fit of the lenses on the eye and the impact that could have on eye health must be evaluated. Once a good fit is achieved, then the fun with colors can begin! It is important to actually try on the colors in which you're interested because different colors have different appearances on each individual.

There are many colors available from a number of different lens manufacturers. Some of the colors include the more traditional blue, brown, green, and hazel. There are also colors like violet, honey, gray, and aqua. There are colored lenses available in spherical and toric (for astigmatism) lenses.

I have astigmatism. What exactly is that and can I wear contact lenses?

Astigmatism is a commonly heard term, but few people know exactly what it is. Like near-sightedness (myopia) and far-sightedness (hyperopia), astigmatism is another condition that is usually correctable with glasses or contact lenses.

Astigmatism is typically a result of the cornea (the clear dome-shaped part that covers the colored part of the eye) being shaped more oblong like a football than round like a basketball. Because of this variation in curvature, when light enters the eye, it focuses in more than one place. To correct for this, we put two powers in the glasses or contact lenses in order to allow all the entering light to focus in one spot to give you the best, clearest vision possible.

In the past, patients with astigmatism were more difficult to fit with contact lenses. But with today’s technology, most people can successfully be fit into soft toric lenses or rigid gas permeable (RGP) lenses. With soft lenses, the type of lens is dependent on the amount of astigmatism. We have disposable soft toric lenses that correct for low to moderate amounts of astigmatism, as well as custom toric lenses that correct for higher amounts of astigmatism. RGP lenses, the newer generation of hard contact lenses, do an excellent job at correcting for astigmatism, too. For lower amounts of astigmatism, often standard lens designs can be used. If you have a higher degree of astigmatism, you may need a design called a bitoric lens.

How would I know if I have an eye infection or a corneal ulcer?

Wearing contact lenses puts you at a higher risk for infections and ulcers. A good "rule of thumb" to keep in mind is the RSVP rule:

Redness -- can be one eye or both

Secretions -- can be tearing, clear stringy mucous, yellow or green sticky mucous

Vision changes -- typically mild to moderate decrease in vision or blurring

Pain -- may be aching, sharp, dull, or just uncomfortable

If you have any of these symptoms, it is essential that you remove your contact lenses immediately. For this reason, it is important to always have an up-to-date pair of back-up glasses. Do not attempt to treat a red eye yourself; go to your eye doctor as soon as possible. Non-preserved artificial tears may be used, however avoid Visine and other "get the red out" drops, and do not use someone else’s eye medications.

I wear bifocals or reading glasses - can I still wear contact lenses?

In most cases, yes! Around the age of 40, give or take, the focusing system of the eye becomes less flexible, a normal aging process called presbyopia. When this occurs, there are a number of contact lens options available to people.

Some people prefer to have both eyes corrected for distance vision and have a pair of reading glasses to wear over the contact lenses in cases where clear near vision is needed. Another option some people are successful with is called monovision. Monovision is where one eye, typically the dominant eye, is corrected fully for distance, and the other eye is slightly undercorrected in order to see up close. Although the eyes aren’t fully working together at all times, the brain learns to adapt, and many people very successfully wear monovision.

There are also bifocal contact lenses available. In general, these lenses provide patients with good vision most of the time, at most distances, and in most lighting conditions. Bifocal contact lenses are available both in soft lenses and rigid gas permeable (RGP) lenses. Within these groups there are two basic designs &endash; alternating and simultaneous. Alternating designs work very much like bifocal glasses where the top portion correct for distance and the bottom portion corrects for reading. There is a definite area of the lens for each working distance. Simultaneous designs allow clear distance and near vision at the same time. Some of these lenses have concentric rings of distance and near correction, while others are more like the no-line glasses (or progressive lenses) and the power changes from the center out to the edge of the contact lens.

The process for fitting bifocal contact lenses can be time consuming because the fit of the lenses, the vision in the distance, and the vision up close all must be considered. If you and your doctor decide that this is the best option for you, be patient with lens changes because the final outcome will be worth it.

What is the best soft bifocal contact lens available on the market?

There is no one "best" soft bifocal contact lens. Different soft bifocals work differently for different people. There are a number of designs available, including lenses that have the distance portion in the center and lenses that have the reading portion in the center. In addition to soft bifocals, there are many rigid gas permeable (RGP) bifocal options. With both SCL’s and RGP’s, patients may be fit with monovision where one eye is corrected for distance and one eye for near. This fitting strategy may incorporate bifocal contact lenses and is then referred to as modified or enhanced monovision.

Your eye care practitioner will select the best option for you based on the measurements of your eyes and your specific visual demands. The fitting process may take several visits in order to find the lenses that work best for you.

What are the advantages and disadvantages of soft contact lenses compared to RGP's (Rigid gas permeable lenses)?

There are so many different contact lens options available today that the choices can become confusing! There are two broad categories of contact lenses, however: soft contact lenses (SCL’s) and rigid gas permeable lenses (RGP’s). Each type of lens has advantages and disadvantages.

Soft contact lenses tend to be very comfortable initially. They drape over the eye, so patients don’t feel them much when blinking. SCL’s tend to stay on the eye without becoming dislodged or displaced. Many people find disposable SCL’s (lenses are worn for a specific period of time &endash; from one day to several months - and then thrown away) very convenient and like knowing they have back-up lenses in case something happens to a lens.

Disadvantages of soft contact lenses include the risk of tearing a lens and less oxygen getting to the cornea than with RGP’s. Some patients experience more dryness with SCL’s.

RGP’s, on the other hand, allow more oxygen to the cornea by they tears flowing under the lenses. They provide very crisp, clear vision, and often people with mild to moderate dry eye find they can wear RGP’s longer and more comfortably than SCL’s. Some studies have shown that children fitted with RGP’s tend to have a more stable prescription than children do in glasses.

Rigid gas permeable lenses are smaller in diameter than SCL’s and are felt more initially by the eyelids as you blink over the lenses. This lid sensation decreases quickly with time, and the final comfort of SCL’s and RGP’s is very similar. RGP’s may become dislodged from the eye or pushed off to the side more easily than SCL’s.

Telling your eye care provider about your visual needs and the types of activities you enjoy will help him or her select the best lens option for you.

I have diabetes. Can I still be a successful contact lens patient?

Diabetes has an effect on the eye, as it does the rest of the body. Most diabetics are familiar with the risk of diabetic retinopathy, complications inside the eye from the disease. It also affects the front surface of the eye, or the cornea. Patients with diabetes may notice dryness more often and more severely than non-diabetic patients.

In some patients, this dryness is not severe enough to prohibit contact lens wear. But dryness is only the initial concern. Diabetics tend to heal more slowly than individuals without diabetes. This is true for the eye as well as other tissues of the body. Contact lenses increase the risk of corneal ulcers and infections, both of which are of more concern to a diabetic patient due to the lengthened healing time.

This does not mean that individuals with diabetes can’t wear contact lenses. Make sure to let your eye care provider know if you have diabetes as it may impact the choice of lenses or solutions. It is also important to remember to follow the wearing and care schedule your practitioner gives you in order to minimize the increased risk contact lenses have for patients with diabetes.