Written by InnovativEyes

Published: 02 November 2018

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 Ophthalmology 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 do before.

The two biggest uses for OCT in ophthalmology 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 (said just about everyone at some point or other in their lives).

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.

Written by InnovativEyes

Published: 14 September 2018

Drug Allergy or Side Effect? Knowing the difference could save your life

There is a common misconception that any adverse reaction to a drug is an allergy. That is definitely not the case.

Reporting to your doctors that you have an allergy to a medication when what you really had was a side effect could potentially create a substantial alteration to your medical care in the future. And this could mean a physician may avoid using a drug that could possibly save your life because of the fear of an allergic reaction.

An anaphylactic allergic reaction generally produces a very specific set of symptoms, including difficulty breathing due to constriction of windpipe, swelling of your tongue and/or a rash and hives that break out over your entire body. While an allergic reaction can present in other ways, these are the most frequent reactions that occur when you have a true allergy to something.

If that is not the type of reaction you had then it probably isn’t an allergy. If you are uncertain if your reaction to a medication is an allergy or not, testing by an allergist may be able to tell you for sure if your reaction was a true allergy or a side effect.

It is not always just the patient who misconstrues a side effect for an allergy. Sometimes it is the doctor or the dentist who tells the patient, “You must be allergic.” This is a quick and easy explanation but not always the correct one.

In Ophthalmology there are not a lot of “lifesaving” incidences but there are several drugs that are the preferred treatment for certain conditions and if you report an allergy to these drugs it may make your doctor use a much less effective drug.

Here are some of the specific examples of when a false report of an allergy may lead to less effective treatment or even failure to offer life-saving treatment.

Epinephrine

The most common potential “lifesaving” drug to which patients sometimes report an allergy to is Epinephrine.

The story usually goes something like this: “I was having a dental procedure and soon after the dentist injected my mouth with a local anesthetic of lidocaine with epinephrine my heart started racing and pounding out of my chest and I almost passed out.” This hypothetical patient may come to the conclusion or the dentist may mention that the patient is allergic to epinephrine. That reaction is almost never an allergy but a side effect that occurs when a substantial dose of the lidocaine and the epinephrine gets into the blood stream and stimulates the heart.

The mouth and gums are very vascular, and it is easy to have some of that injection end up in the bloodstream, but that reaction is not an allergy and should not be reported as such.

Epinephrine is used to treat severe (anaphylactic) allergic reactions and not using it if you were to ever have a severe allergic reaction could lead to some very bad outcomes. This is not to say you can’t be allergic to epinephrine. You can, but it is extremely rare. If there is any doubt you should be tested by an allergist before you ever record yourself in a medical setting as being “allergic” to epinephrine.

Cortisone/Steroids

Cortisone is a highly effective drug to treat many conditions. Again, it is unlikely but not impossible to be allergic to it.

We all have naturally occurring cortisol circulating in our bodies and cortisone is a very similar molecule but not exactly the same. Cortisone also can have a wide range of side effects depending on where and how it is administered

Some of the common side effects of cortisone, which have been mislabeled as an allergy, are: Making your blood sugar rise, insomnia, mood swings, nausea, and weight gain. These are all known side effects of the drug and not allergies. Cortisone side effects are associated with only certain routes of administration and are often dose dependent.

Why is this important in terms of your eye care? We often use cortisone derivatives, like Prednisolone, to fight inflammation that may occur in your eye, particularly after any ocular surgery. If you report that you are allergic to cortisone when you really only experienced a side effect we are going to have to use a less-effective medication to deal with your eye inflammation.

As I mentioned above, most side effects are dose dependent and the dose you got in a pill may have caused a side effect you’d rather not have again but the dose in an eye drop is significantly less and highly unlikely to give you the side effect you got with a pill taken orally.

Antibiotics

People often report they are allergic to antibiotics when they really experienced a side effect.

The most common side effect with oral antibiotics is some type of gastrointestinal disturbance, like nausea, or diarrhea. If that was what you had and just prefer not to get that again you still shouldn’t report it as an allergy. If you do, then the drug can’t be used as an eye drop or ointment that might be the best treatment for your condition.

An antibiotic eye drop/ointment is very unlikely to produce the same gastrointestinal trouble that the same antibiotic gave you when given as a pill. You don’t want to take away the most effective treatment for your problem because you mislabeled a side effect as an allergy.

Sedatives/Anesthesia

Most of the time with these drugs the issue is how you felt either during or after a procedure.

Common comments are “it took me too long to wake up” (side effect not an allergy); “the sedative I got in my IV burned when it went in” (side effect not an allergy); “I was sleepy all day” (side effect not an allergy); “I was nauseous after the procedure” (could be an allergy but much more likely to be a side effect).

Why are these important? We can make you much more comfortable for a local anesthesia procedure if we can use some sedation. Using sedation may be better for you and the doctor performing the surgery because you are much less likely to move during the surgery if you are resting comfortably.

If you ever have an untoward reaction to a medication it is worth your time and effort to really probe into the issue to figure out if what you had was really an allergy or just a side effect because sometimes your life may depend on it.

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