So, if you’re watching this video, there’s a good chance that you have heard the term ‘astigmatism’ and perhaps you’ve heard that every single time you go in for your eye exam. Well, in this video, we’re covering exactly what astigmatism is how astigmatism affects our vision and our prescriptions. So, let’s take a look. Hey, guys! This is Doctor Joe Allen from DoctorEyeHealth bringing you the very best in tips and education about your eyes and your vision and here on this channel you’ll find a lot of different product reviews as well as educational videos just like this one so if you’re new here, considering subscribing and at any point in the video make sure to check out the show notes and links below for further information about anything we forget to mention. Otherwise, let’s go over astigmatism. So astigmatism is arguably one of the most common things I have been talking about with my patients every single day. It’s a very common diagnosis and it is something most of us, probably have to some degree. The most simple way to explain astigmatism is basically that the structures within the eye are not perfectly round; they’re a little bit warped and because of that, it causes light to bend or refract a little bit uneven inside of the eye and that causes your vision to be blurry, and distorted. However, the good news is that astigmatism isn’t actually a disease, it’s just a condition, and we can correct for that with glasses, contact lenses, and even eye surgeries, like LASIK. Now, to better explain what astigmatism is, I want to show you the cornea. The cornea is the front window surface to the eye. It protects the inside of the eye from the outside environment, and acts as a lens to bend light toward the inner eye. In an ideal world it is a smooth and evenly curved surface to that light passes through it in a uniform fashion. However, most of us have some unevenness on the surface of our cornea, and that uneven curvature is what is called corneal astigmatism. The uneven curve of the cornea can be determined by finding the difference between the flattest and the steepest curve of the corneal surface. Most corneas have some curvature somewhere between 39 and 49 diopters and that number tells us the amount of curvature or power that the cornea has to bend light. If there isn’t astigmatism, as in this example, we’ll say maybe the curvature is 43 diopter in one place and maybe 41 diopter in another. The amount of astigmatism in this example being the difference being between 43 and 41 is two so the answer is 2 diopters of corneal astigmatism. Now, your eye doctor can actually measure this curvature to the eye using a couple of different instruments. Classically, we would use one called a Keratometer which only measure about the first three millimeters centrally of the cornea. But nowadays, we actually use new technology called a topographer, and the topographer will not only just measure the central three millimeters, but they’ll measure but they’ll measure the entire front surface of the cornea making it a little bit easier to identify disease as well as to treat and manage those conditions, such as with specialty contact lenses or even with corrective eye surgery. Now, when light passes through a cornea with astigmatism, that causes the light to be focused irregularly inside and that causes our vision to not just be really foggy and blurry, but can cause your vision to be distorted. Almost in an extreme example, it would look like a fun house mirror, where everything can kind of be wonky and warped. Now most of us are actually born with some level of corneal astigmatism, and it may change in the first couple of months and then it tends to stabilize out for the rest of your life. Now there is another type of astigmatism, and we call that lenticular astigmatism. And that has to do with the shape of the lens inside the eye. And that astigmatism does tend to change throughout our lifetime. First in our adolescent years, as we’re under more visual stress, and then again in our later years as the lens begins to stiffen. Now, when the doctor measures and corrects for your astigmatism, they actually correct for the combination of the two: both the cornea and the lenticular astigmatism. Usually, your doctor won’t measure the lenticular astigmatism by itself because it requires very expensive and high-tech equipment and it really just doesn’t give us that any much useful information. Now, if you don’t know if you have astigmatism or not, we can actually figure that out by looking at your most recent glasses prescription. So, let me guide you through how to read those numbers. So, if we look at a prescription pad here and zoom in here we are going to see, of course, the first and last name, a date of birth, and then down below we are going to have the expiration date and your doctor’s signature. Now, looking here on the left side you will see two rows, one is labeled OD which stands for the right eye and one is labeled OS, which stands for the left eye. On the top, we have several columns which we can actually work through individually, the first column here is labeled as SPH, which stands for sphere, which is the easiest type of lens that can be made. Under that you’ll see some numbers, the higher the number the stronger the prescription. The number will also have a positive or a negative symbol in front of it, which tells us if the lens is correcting for far-sightedness, or hyperopia, when it’s a positive symbol and near-sightedness, or myopia, when it’s a negative symbol. These next two columns here are going to tell you if you have astigmatism. That first column is the cylinder, and the higher the cylinder number, the stronger your astigmatism correction will be. Again, in front of this number you may see a positive or a negative symbol. However, it is more common to have a negative symbol here because when an optician makes glasses, it has to be in the negative format. If your prescription does have a positive symbol here, well, then your optician has to do extra work to convert it and it increases the likelihood of errors when glasses are made. The next part is called the axis, and the axis number indicates the position of the overall astigmatism through the visual field. And this number will be between 0 and 180. To illustrate this better, we can divide the eye into a pie with twelve equal sections. The astigmatism lies along one of the divisions of this circle. In this case, the astigmatism is along the 120-degree line in the right eye, and 20-degree line in the left. The axes are darkened on the illustration to indicate this. It is actually more common for the prescription when we are young to have an axis closer to the 180 line, and then gradually becomes closer to 90 as we age. So, if you have these number, that’s going to tell you that you have astigmatism. However, the last two sections here describe what is called the add or the additional lens needed to help someone see up close as in the use for bifocals, and the there’s the prism which isn’t used very often, but is necessary for those individuals who have fusion difficulties and may end up seeing double. Now, the good news is that we can correct for astigmatism with glasses, contact lenses, and again forms of corrective surgery like LASIK. The most simple way to correct for astigmatism is with glasses. However, glasses aren’t always the best way to correct for it because we can get some optical distortions because they’re looking through a piece of glass or plastic. And you can kind of experience that distortion by holding up your lenses and looking at a distant object that’s straight up and down. And then rotating the lenses so you can see how the world starts to warp left and right or side to side. And that’s why some people will say that it feels like they’re almost having tunnel vision while looking through glasses as compared to some options, like contact lenses. Contact lenses are fantastic because it actually forms to the surface of the eye, giving you a wider field of view, and can correct for that astigmatism, all at the same time. Now, most contact lenses for astigmatism may actually be called toric lenses and these lenses have a little dash mark that’s etched into the lens and you can hold up the lens to the light and sometimes you can see that little marking. That mark is there so that the doctor can read where the lens is sitting on the eye, and then make adjustments so that you can get the best prescription and comfort in those lenses. Many types of corrective eye surgery can actually correct for astigmatism as well ,such as LASIK. LASIK can actually actually correct up to almost 5 or 6 diopters of astigmatism. So, make sure you ask your doctor if you are a good candidate for those procedures. Now, let me show you what somebody sees when they’re not wearing correction for their astigmatism. I’ll give you the best frame of reference we have a vision chart in the clinic here on the left side and we have some distant objects outside here on the right. We’ll start off to showing what 1 diopter of corneal astigmatism set at about and axis 90 degrees looks like and then we can rotate it so the axis is closer to 180 degrees. We can also do the same thing with 2 diopters of corneal astigmatism, and then we can go over to 3 diopters and then over to 6 diopters. And here at 6 diopters, you can see how warped or bent someone’s vision would be if they were walking around without correction for their astigmatism. Now, again the good news is that astigmatism isn’t really a disease, it’s just a condition that we correct for. However, there are some extreme cases where people will have really high levels of astigmatism and that can actually be classified into diseases. One of those diseases is called Keratoconus, where the surface of the eye, the cornea, actually starts to bulge out into a shape of a cone. Other cases such as Pellucid Marginal Degeneration describes where the cornea begins to thin inferiorly, causing again high levels of astigmatism. Now some people may have had trauma to the eye or scarring that actually caused astigmatism and that again can be corrected with special contact lenses and maybe even just glasses by themselves. Alright, guys, thanks for checking out our video about astigmatism and how it affects your eyes and your vision. If you like what you saw, make sure to hit that like, subscribe and go ahead and share this video with friends and family who may be interested more in what astigmatism actually is. Otherwise, again, this is Dr. Joe Allen from DoctorEyeHealth, bringing you the very best in tips and education about your eyes and your vision. Keep and eye on it! We’ll talk to you soon. *beep* *woo sounds* putting on my cool glasses. Putting on my cool glasses. Ooh, it felt good!