Podcast Episode #6 – Refractive Error (Myopia, Hyperopia, Astigmatism, and Presbyopia)

Welcome to The Bright Eyes Podcast: Advice for Healthy Vision for All Ages.  Your hosts are Dr. Nate Bonilla-Warford & Dr. Beth Knighton, residency-trained optometrist that provide eye exams for glasses and contacts, and specialty services including vision therapy, myopia control, orthokeratology, and sports vision training.  Their mission to empower patients by providing the best in friendly, professional, and individualized eye care.

In this episode, Dr. Nate talks about Refractive Error and explains how they affect how people see. Specifically Myopia, Hyperopia, Astigmatism, and Presbyopia. 

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Intro:                     Welcome to the Bright Eyes Podcast: Advice for healthy vision for all ages. Your hosts are Dr. Nate Bonilla-Warford and Dr Beth Knighton, Residency trained optometrists providing eye care to all ages.  With exams for glasses and contacts and specialty services including vision therapy, myopia control, orthokeratology and sports vision training. Their mission is to empower patients by providing the best in friendly professional and individualized eye care.

Dr. Nate:              From Tampa Bay Florida it's the Bright Eyes podcast.  This is episode number 6. I am Dr. Nate Bonilla-Warford and I'm going to be talking about "refractive error".   I know that this is an area that confuses a lot of people. People will get a prescription for glasses or contacts and they'll say "What does this mean? What does this number mean?" Or they'll say "I think I have an astigmatism." like it's some sort of dreaded condition, which it really isn't.

Dr. Nate:              So  when we talk about refractive error -  refraction means the refraction of light.  It's how light is focused.  And error just means that it's not focused accurately. What I want to explain first of all is that these conditions that we're going to talk about are not a disease the same way glaucoma and cataracts are.  However different diseases can cause different refractive errors. What the refractive error is is all about the shape of the eye. People may have heard different things about the shape of their eyes such as their eyes shaped like a football or their eyes are too long or too short. And that's what we're going to talk about now.  More or less,  your eyes around. They are more like a sphere. Light enters your eye through the cornea, the clear front part. It travels through the pupil and is focused through the lens to focus clearly on the back of the eye,  which is called the retina, as the light goes through the cornea lens to the back of your eye.

Dr. Nate:              If the light isn't focused correctly,  your brain will see this as a blurry or distorted image. And this is what we mean when we say refractive error.  Eye doctors can measure this in a variety of different ways. The most common way that we think about measuring this is the "which is better 1 or 2" test. However we can do this without patients saying anything this is what we do with infants and young children where in this case we shine a light in their eyes and we measure the refractive air as it bounces back out of their eyes. We also have diagnostic equipment which measures the same things. All of these procedures are done during the standard eye exam which we recommend every year not only to evaluate refractive error but to see if there's any underlying diseases or conditions.

Dr. Nate:              So  what we're going to do here is have one of my vision therapists Myriam read the definition from the National Eye Institute of different types of refractive error and then I'm going to talk about them.

Myriam:               Myopia aka nearsightedness is a condition where objects up close appear clearly,  while objects far away blurry.  With myopia, light comes to focus in front of the retina instead of on the retina.

Dr. Nate:              Now, I know this gets a little confusing because we're talking about near-sightedness and that means you can't see far away. We're defining the condition based on what you can see even though the problem is something else. And that sounds sort of weird... myopia, near-sightedness, is probably the most commonly recognized type of refractive error. This is the one that a child may have trouble seeing the board at school and so they come in and they get an eye exam. People may have trouble driving or seeing the menu on the TV for one reason or another. Their eyes have gotten too long and the light focuses in front of it giving them blurry vision far away. So we deal with this in a short term and long term fashion. In the short term, we need to provide clear vision so people can function and this can happen in the form of glasses or contacts or orthokeratology or LASIK or other different kinds of procedures.  And that's important so that they can do the things that they need to do in life. Now for the long term perspective, myopia tends to get worse over time. And so we sometimes need to do some things to keep that rate slow so it doesn't get worse very dramatically and we're going to have several different episodes in the future talking about that.

Myriam:               Hyperopia AK farsightedness is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience differently. Some people may not notice any problems with their vision especially when they're young. For people with significant hyeropria, vision can be blurry for objects at any distance, near or far.

Dr. Nate:              Now this one is even more confusing because we talk about far-sighted meaning they can see far away. But in this case most people can also see up close. And the reason is, unlike myopia or near-sightedness, where you can't really do anything other than just sort of squint with hyperopia,  or farsightedness, your eyes can adjust and focus to make it more clear so when you're looking at something far away or up close your eyes can work a little bit harder and make that clearer. The problem is if your eyes have to work very hard in order to see clearly then your eyes either get tired vision gets blurry or or it creates other problems where maybe there's double vision or other issues. as with myopia, the most common ways to treat this are either glasses or contacts.  Although there are other issues as well.

Myriam:               Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light sensitive tissue at the back of the eye. This can cause images to blurry and stretched out.

Dr. Nate:              Astigmatism really does sound like an affliction that people have but really all it means is when the light is focused on the back of the eye because the curvature is not uniform. It's different in different places of the eye the eyes literally see multiple images and it is distorted or it looks confusing.  And so people will say that they sometimes see double or their vision is smeary or their vision is blurry and that isn't a disease. It just has to do with the shape usually of the front part of the eye and so they can wear glasses or they can wear special contacts which are called toric lenses for astigmatism or other procedures to give them clear vision unlike near-sightedness and farsightedness astigmatism affects everything near and far, sometimes more one worse than the other. This is the one where people will say "My eyes are shaped like a football" and the reason why that analogy exists is because football is longer on one side than it is on the other.  So it gives this non-uniform curvature but people's eyes aren't really shaped like footballs. It's just an example.  I prefer to use the example the side of an egg because I think it's a little less pointy than a football.

Myriam:               Presbyopia is an age related condition in which the ability to focus up close becomes more difficult as the ages. The lens can no longer change shape enough to allow the eye to focus close objects clearly.

Dr. Nate:              And so we get to the last one which is presbyopia which people confuse especially with farsightedness because it's a problem of having to see up close. The main difference is where and hyperopia the eyes too short for the light to focus on the back of the eye, with presbyopia, it is that over time the lens of the eye isn't as flexible due to age and so people need either reading glasses or bifocals. Most people know somebody who's in their 40s or 50s who have to carry around glasses to be able to see a little bit more clearly a close reading a menu reading a book etc.

Dr. Nate:              So that's a quick summary of refractive error and we're going to talk more about all of these different things in future episodes.  Thank you for listening. if you have any questions comments or suggestions or you can email us at office@Brighteyes Tampa.com.

Outro:                   Brought to you by Bright Eyes Family Care and Bright Eyes Kids. Find previous episodes and more detailed information and BrightEyesTampa.com. Creative Commons copyright attribution non-commercial use. The only purpose of this podcast is to educate and to inform, It is no substitute for professional care by a doctor experienced in the area you require. This podcast is provided on the understanding that it does not constitute medical or other professional advice or services. Please consult physician for diagnosis.

Intro/outro music: Lucas Warford of Three For Silver.