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Visual Field

The visual field test is designed to see how well you see outside of the center part of your vision (peripheral vision).

When we test your vision on the basic eye chart it is only testing how well you see right in the center and gives us no idea if you can see out away from the center. Your peripheral vision is very important because it gives you the ability to move around your environment without running into things.

There are several diseases that can severely impact your peripheral vision while leaving central vision unaffected. Some people can have perfectly normal 20/20 central visual acuity and have almost complete loss of their peripheral vision.

The main culprits that can have a big impact on your peripheral vision long before your central vision are glaucoma, some retinal diseases such as retinal detachments or retinitis pigmentosa, and some neurological problems like brain tumors, strokes, pseudotumor cerebri and multiple sclerosis.  

Most visual field tests are now done on an automated machine that flashes lights in your peripheral vision while you stare straight ahead. The lights continue to get dimmer until you can no longer detect that they are there. The machine is trying to find the dimmest light you can see at each point in your peripheral vision that it is testing for.

Many patients get anxious when they take this test because everyone wants to do well on it. That sometimes results in people not staring straight ahead but trying to look around to find the lights in an effort to do better.

That just makes the test come out worse. The machine also makes some noise as it changes location of the test light. Some people start pressing the buzzer whenever they hear a noise. They think there must be a light they missed but the machine, several times during the test, makes noise and then doesn’t put a light on to specifically see if you are trying to cheat by hitting the buzzer on the noise rather that seeing the light. Don’t do those things - you are only cheating yourself and making it more difficult to figure out your problem.

Ocular Coherence Tomography (OCT)

The OCT really took hold in eye doctors' offices at the beginning of this century. It was the first time we were able to see anatomy and pathology inside the eye on a microscopic level without the use of any radiation.

It has been a great addition to our examination techniques and allowed us to see many causes of vision loss at a level of detail we could never have before.

The two biggest uses for OCT in optical health are diagnosing diseases of the retina, particularly the area of central vision called the macula, and for diseases of the optic nerve, the most common of which is glaucoma.

For retinal disease it has been extremely helpful in macular problems such as macular degeneration, the leading cause of blindness in the U.S., diabetic retinopathy, retinal vascular occlusions and retinal swelling from inflammation.

The OCT allows us to see the individual cellular levels of the retina and helps in diagnosing the exact level where the pathology is occurring. If you look into the eye at the retina and see some bleeding in the macula it is difficult to judge where that blood exists. Is it superficial in the retina and coming from the retinal circulation or is it deep in and coming from the choroidal circulation under the retina?

The difference between those two locations can have a significant impact on what disease is causing the problem and what the proper treatment is. The OCT is also very helpful in following the effect of treatment. If you are treating a bleeding or swelling problem in the retina, the OCT can track the degree of improvement with a level of detail that could never be matched by the human eye.

For glaucoma and other problems with the optic nerve, the OCT can very precisely measure the thickness of the nerve tissue as it passes through the optic nerve. The hallmark of glaucoma is progressive loss of nerve fibers in the optic nerve.  Being able to measure the nerve thickness down to the micron level is very helpful in both diagnosing and watching for progression of any optic nerve disease.

Fundus Photography

A picture is worth 1,000 words...

Fundus photography is just that, a regular picture of the inside of your eye. The pictures highlight the appearance of the macula and the optic nerve and record it for prosperity.

As eye doctors we make notes in the medical record of what we see when we look in the eye. The wording of anything that looks abnormal with the retina or optic nerve does vary somewhat from doctor to doctor. One of things we record is something called the cup to disk ratio (C:D) of the optic nerve. We express that ratio as a percentage. Normal is about 30% or .3. The range of normal is very wide and some “normal” eyes have a .1 cup and others can have a .7.

In glaucoma those percentages get larger over time as the person loses nerve tissue. So, if you were born with a .3 cup but in your 60’s you were found to have a .5 cup that would be a strong indicator that you might have glaucoma.  However, if you were born with a .5 cup and at 60 you still have a .5 cup then you don’t have glaucoma.  When you look at someone at 60 with a .5 cup it’s hard to be sure if this is normal for that person or did they progress from a .3 cup to a .5 cup.  If only I had a picture …  

Pictures of the back of the eye really do tell the story better than words. I can describe what the C:D looks like to me but a different doctor may describe it differently. Doctors are usually fairly consistent in their estimate of the C:D when it is the same doctor watching that C:D over time. When a different doctor estimates the C:D that consistency is just not there. My .4 C:D may be my partner’s .5. But you can’t argue with the picture.  

The same thing occurs with retinal bleeding. Rating the amount of bleeding as mild, moderate or severe is somewhat helpful but there is a broad range of “mild” or “moderate”. When comparing two pictures taken at two different points of time it is much easier to decide if something is really getting better or worse.

We also use fundus photography to keep an eye on small tumors that can develop in the eye called choroidal nevi. These are increased areas of pigmentation under the retina in an area called the choroid. Most eye doctors explain these pigmented spots a “freckles in the eye”.  Most choroidal nevi are small and fairly flat. They can, however, sometimes grow larger and rarely turn into a melanoma in the eye. Serial photographs are very helpful in watching the lesions for growth.

These three tests - visual field, OCT and fundus photography - make up the core of our testing. There are many other tests that can be performed along with your eye exam but these three we described here probably make up about 80% of the tests you may encounter, depending on your individual problem.

Article contributed by Dr. Brian Wnorowski, M.D.

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Ask Dr. Stewart Your Eye Care Questions

What can be expected during a contact lens fitting?

A patient can expect to have a different experience when having a contact lens fitting. In addition to the eyeglass exam, questions will be asked to determine which contact lens will work best for them. Will they want to leave the lenses in their eyes overnight or will they remove them every day? Will they wear them only occasionally or will they be for everyday use? Do they want a contact lens that they throw away every day or do they want a contact lens that they have to clean and disinfect? If the patient is over age 40 and has a compromised ability to see up close, how will they see up close with their contact lenses? Will they wear readers over their distant contacts, or will they wear multifocal contacts, or will they wear monovision?

Are some people more prone to having Dry Eyes than others?

Experiencing dry eye symptoms is more common as we grow older, particularly in people 50 years of age and older. Hormonal changes in women who are experiencing menopause or who are post-menopausal. Inflammation in our body can affect the tear gland's ability to produce tears. Eye or health conditions such as glaucoma, diabetes, lupus, rheumatoid arthritis, and Sjogren's Syndrome can be associated with Dry Eyes. Environmental conditions such as dry winter air, dry indoor heated air, working on the computer, and wearing contact lenses can cause Dry Eyes.

Are there advantages to single-use contact lenses? What are they?

Single-use daily wear contacts are convenient to the patient and a healthy recommendation from their eye doctor. At the end of the day, the patient only has to dispose of the contacts. There is no need to take the contacts out to clean and disinfect them. The patients time and money spent on solutions and caring for them are eliminated. Not to mention that the next time they wear a contact, they will be wearing a brand new contact! The single best recommendation your eye doctor can make is to recommend single-use daily wear contacts. They are the healthiest contact that can be worn. The contact lens pathology issues of wearing the same contact for two or four weeks such as neovascularization, microcystic edema, and bacterial infections are greatly reduced.

What is an eye infection?

Your eyes can get infections from bacteria, fungi, or viruses. Eye infections can occur in different parts of the eye and can affect just one eye or both. Two common eye infections are conjunctivitis (also known as pink eye) and lid styes which are swollen lid bumps that can also be painful. Common signs of an eye infection are pain, itching, or a sensation of a foreign body in the eye, photosensitivity, redness or small red lines in the white of the eye, discharge of yellow pus that may be crusty upon awaking, and tears.

What happens during a typical Diabetic Eye Exam?

Your Eye Doctor will evaluate the back of your eye called the Retina to check for leaking blood vessels. Diabetic retinopathy occurs when elevated blood sugars damage the walls of the blood vessels. The vessel walls may thicken, leak, develop clots, close off, or grow balloon-like defects called microaneurysms.

My eyes tear all the time. Why do you call it Dry Eyes?

Your eyes have extra tears because your eyes produce extra tears to combat irritation and dryness. A better way to describe Dry Eyes is tear film instability, which refers to the composition of your tears not being in the proper composition. Stopping eyes from producing extra tears is a goal in the treatment of Dry Eyes.

At what age should my child have his/her eyes examined?

If you ask 10 different Doctors you will get 10 different answers. Newborns have their eyes checked in the birthing ward for starters. From birth to age 5 their eyes are growing. At age 5 is a good time to schedule a regular eye examination, however, if any unusual eye behavior is observed under age 5 an eye exam should be scheduled at that time. Unusual eye behavior such as eye squinting, a head tilt, or having to get close to see.