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Patient Education

Glasses and Contact Lenses

What is refractive error (myopia/hyperopia)?

Refractive error is the error in the focusing power of the eye. Light in the eye's optical system is focused by the cornea and then the lens before being imaged on the retina. If the image is focused properly on the retina, the eye is said to emmetropic. If light is improperly focused in front of or behind the retina, then one is said to be myopic (near-sighted) or hyperopic (far-sighted). Focusing power can be adjusted with the use of glasses, contact lenses, or refractive surgery (LASIK, PRK, phakic intra-ocular lenses, etc), and this is how we are able to help people who are naturally myopic or hyperopic see well.

Why is my vision better with my old glasses compared to my new glasses, even though the prescription is the same?

Each pair of glasses focuses light slightly differently depending on production method, material, how the glasses sit on the face, tilt of the head, etc. This tends to be particularly noticeable in progressive lenses (blended bifocals, no-line bifocals, etc.) because of the blending process. In addition, some people are more sensitive to these differences than others. If you have concerns about your glasses, please check with the store where you purchased them to confirm that the measured lens power is the same as your written prescription. If you have further questions about the prescription, we are happy to help you check them as well.

Are there any risks to wearing contact lenses?

Yes! It is a misconception that glasses and contacts are equivalent in terms of safety. Contact lenses carry certain risks, including infection, scarring, inflammation, and in rare cases, permanent loss of vision. As a corneal specialist, Dr. Chen has a unique perspective on contact lens complications because he has treated the worst kinds of contact lens-related problems.

It is important to realize that, even if you do everything right with your lenses, you can still develop contact lens-related problems. Sometimes these problems can occur even without you seeing any difference in your vision or experiencing any pain. These complications are the reason we stress patient education, meticulous eye care, and regular follow-up. There is a reason that contact lenses are an FDA-regulated medical device and require a doctor's prescription to purchase! We believe strongly that anybody wearing contact lenses should be seen at least every year to monitor for any long-term contact lens-related problems. If you have any questions about your contacts, please speak to your prescribing doctor.

We recommend that you read what the FDA has to say about contact lenses here.

Medical Eye Problems

Why is my eye red?

The "red eye" is one of the most common reasons patients come to see us. Sometimes redness can be due to something as mild as dryness or allergies. However, other causes of the "red eye" include infection and inflammation, both of which can be sight threatening. The only way to make this determination is to be examined by an eye doctor. Other symptoms that would be more worrisome and therefore urge you to seek immediate attention include worsening of vision, pain, or discharge.

What is a cataract?

The eye contains a crystalline lens that helps to focus light on the retina, the part of the eye responsible for seeing. As we get older, the lens changes in color and/or consistency, which can lead to the blockage of light. This is what is known as a cataract. Depending on the changes seen in the lens, it can be described as nuclear sclerotic, cortical, or subcapsular (amongst other descriptors), depending on its appearance. Cataracts are a gradual progression and may not initially affect vision but in most people a cataract will eventually interfere with their vision.

We consider performing cataract removal surgery when the vision starts to be affected. Each individual's visual needs are different, and therefore the timing of cataract surgery should be custom tailored to each person's desires. In rare circumstances, cataract surgery can be urgent because of medical considerations. However, this is the exception rather than the rule and, in the vast majority of cases, cataract surgery is not an emergency.

Why do some people need glasses after cataract surgery while others do not?

During cataract surgery, the natural lens is usually replaced with a synthetic lens. Eye surgeons (ophthalmologists) custom select a lens for each patient based on the patient's visual desires as well as calculations based on eye measurements.

Some people require glasses after surgery for distance vision (such as driving) and some do not. This depends on a lot of factors. First, lens calculations are based on eye measurements that are, by nature, imperfect. If the data measurements are even a hair off, this can affect the final prescription needed after surgery. Second, the eye is a living tissue that responds to surgery by healing. Each person heals differently and therefore certain aspects of the eye that impact total focusing power cannot be predicted. Third, each person's needs and expectations of their vision can be different. Some people are very sensitive to even the slightest imperfection in their vision, while others tend to be more easy going.

Will I need reading glasses after cataract surgery?

Most people require glasses for reading after cataract surgery with conventional lens implants. This is because the eye needs a different focusing power for up close than it does for distance and a conventional lens implant can only focus for one distance. When we are young, our natural crystalline lens can focus at many distances, but as we age, our natural lens gradually loses its ability to focus at many distances until it can eventually only focus at one distance as well. This is why most people require reading glasses or bifocals when they reach their 40's, and why most people require reading glasses or bifocals after cataract surgery. There are newer technology lenses that are able to focus vision at different distances and can reduce the need for glasses, sometimes even eliminating the need for glasses. However, like most things in life, you have to give up something to gain something and these lenses have their drawbacks as well. In addition, these lenses are not covered by the vast majority of insurance companies at this time (including Medicare) and are therefore an out-of-pocket expense.

General Medical Problems and The Eye

How does diabetes affect the eyes?

Diabetes is a problem with sugar regulation in the body which can have affects on many organ systems. In the eye, diabetes can cause a number of problems, including blurriness, changes in glasses prescription, bleeding, leakage from blood vessels, and the formation of scar tissue, among other things. Some of these changes are reversible, but in some cases they can be so dramatic that the vision can be permanently affected. The frequency of these eye exams depends on a number of factors, including the success of blood sugar control and findings of previous eye exams. Excellent blood sugar control and regular eye exams are the key to good eye health in diabetics. In general, eye MDs recommend that these exams be performed at least once per year and more frequently if you have had diabetic eye changes in the past.

How do inflammatory diseases (rheumatoid arthritis, lupus, etc.) affect the eye?

Inflammatory diseases can show up as inflammation in the eye, just like any other part of the body. Redness, pain, and blurry vision can be some of the symptoms that you can experience if you have inflammation in the eye. Sometimes, the medications used to treat inflammatory diseases can have side affects in the eye as well. Plaquenil (hydroxychloroquine) is one of the most commonly used medications for inflammatory disease that can affect the eye. If you are on Plaquenil or a similar medication, you should talk to your eye MD about what monitoring may be necessary.

Other Resources

American Academy of Ophthalmology
American Board of Ophthalmology
Federal Drug Administration
National Library of Medicine
National Eye Institute
National Institute of Health