If you have been struggling with astigmatism or you have a loved one that got diagnosed with it, and you want to find out more about the condition, you came to the right place. We prepared a full guide to help you understand what astigmatism is, what are its causes, how does it manifest, what are the effects associated with it, and more importantly, what are the treatment options. Let’s begin!
What Is Astigmatism?
Astigmatism is a rather common condition of the eye, that is not actually a disease or an infection, but a refractive error. But what does that mean? It means that your cornea (the front surface of your eye) is differently curved on one side than on the other. For instance, your eye should normally be shaped like a sphere, but if you have astigmatism, it will most likely be shaped like the back of a spoon or like a football. This causes one meridian of your eye to be more curved than the one perpendicular to it. This may sound complicated, but it is actually quite simple. A meridian is what connects the 2 and 8 or the 12 and 6 on an analog clock.
The problem with this irregular shape is that the light that would normally refract evenly into one place upon entering the eye of a person that is not suffering from astigmatism, making that person perceive objects clearly, does not do the same if you have this condition. Because of the bent shape of your cornea, the light is refracted on two points of the retina, causing objects to only be partly focused. But the good news is that it is a mild condition that is usually easily treatable. But before we go into more details about the treatment options, let’s take a look at what causes astigmatism, what are the most common types, and how does it manifest.
What Causes Astigmatism?
The exact cause of astigmatism is not known. Scientists are unsure of what makes a person with an irregularly curved cornea, while other don’t seem to be having this problem. Even so, there seems to be a higher probability of a child being born with astigmatism if one or both parents are suffering from it so the most common theory is genetics is the cause. Also, babies being born prematurely or with a low body weight have more chances of having this condition.
Astigmatism can be caused by certain surgeries or eye injuries that affect the cornea, and also by a condition called keratoconus, which causes the cornea to gradually become thiner, changing its shape. The condition is associated with an irregularly shaped cornea. If the cornea does not have a perfect curve, light will not refract equally into your eye, causing the retina at the back of it to form an imperfect image of whatever you are looking at.
People also have astigmatism because of the shape of the lens inside the eye is not round. This is called lenticular astigmatism. If the lens does not have a perfect curve, the image refracted in the retina will not be clear. But this means that your cornea is not irregularly shaped, just the lens. This can happen more with people who suffer from diabetes, because high blood sugar levels usually change the shape of the lens. But the damage is not permanent, once you receive treatment and the blood sugar levels go back to normal, so will the shape of the lens.
Types of Astigmatism
There are several types of astigmatism that a person can have, but the three most common ones are myopic astigmatism, hyperopic astigmatism, or mixed astigmatism. Myopic astigmatism is characterized by one or both main meridians of the eye (remember the analog clock?) being nearsighted. This means that objects that are close to you seem clear, but those who are far away become blurry. In hyperopic astigmatism, one or both main meridians of the eye are farsighted, which means that objects that are far away are easier to see clearly, while those who are close to you look blurry. The mixed type of astigmatism means that one of the meridians is nearsighted, and the other one is farsighted.
If we were to categorize types of astigmatism from another point of view, we would get two different types: regular astigmatism and irregular astigmatism. Regular astigmatism (the most common one) is characterized by the meridians being perpendicular to each other, while in irregular astigmatism, the meridians are not perpendicular. The latter is mostly caused either by an eye injury, or by surgery or keratoconus.
Symptoms of Astigmatism
But how do you know if you have astigmatism or not? Usually, when you get blurred vision or objects become distorted and you have trouble focusing on them. This effort your eye makes to focus can lead to eye strain and headaches. You can also experience photophobia, which is sensitivity to light. Fatigue or eye squinting can also be a sign that you have astigmatism and you should contact an eye doctor as soon as possible. Although there are other eye conditions that can have similar symptoms, the only way you’re going to know for sure is if you have an eye exam.
How Is Astigmatism Diagnosed?
The only way to diagnose astigmatism is to go to the eye doctor for an eye exam. Once you go there, the doctor has the possibility to conduct several eye tests in order to determine if you have astigmatism or not. Some of these tests include:
- Astigmatic dial: The doctor shows you a series of lines that form a semi-circle, and if you have no trouble seeing all the lines clearly, that means you have perfect vision. But if you see some more clearly than others, then that may be a sign of astigmatism.
- Visual acuity test: This is the most common type of eye test performed at every eye exam. You will have to read some letters and number of different sizes from a chart.
- Keratometer: This is a device that measures the amount of light reflected on your cornea, to see if the cornea is abnormally curved or not.
- Keratoscope: This device projects rings of light on your cornea and then it measures the space between the rings to see if your cornea is curved, and to what degree.
Treatments for Astigmatism
Now that we have looked at what astigmatism means, what are its causes, how can you tell if you have it, and how you can diagnose it, all there’s left to do is look into the treatment options. First of all, if you are suffering from a really mild case of astigmatism, no treatment might be an option suggested by your eye doctor. But if the problem is more severe, there are two main types of treatment available: corrective lenses and laser eye surgery.
Corrective lenses can either mean contact lenses or eyeglasses. In both cases, the lenses used are designed to bend the rays of light coming towards your eye in such a way that it counteracts the effects of your irregularly shaped cornea. This will allow you to see objects clearly. There are two common types of contact lenses available for people who have astigmatism.
- Gas permeable contact lenses: These lenses use a type of plastic called a polymer, which does not stop oxygen from reaching your eye. Why is this useful? Because oxygen reaching your eye can prevent the risk of blood vessels developing and obstructing vision.
- Soft contact lenses: Made up of a combination of polymer and water, forming a hydrogel, these lenses also permit oxygen to reach your eye.
Laser Eye Surgery
A more definitive treatment for astigmatism, laser eye surgery corrects the shape of your cornea. There are also three types of laser eye surgery (or refractive surgery) for patients who have astigmatism:
- Laser-assisted in-situ keratomileusis (LASIK) surgery: In this surgery, the surgeon uses an instrument called keratome or a special laser to make a thin, circular cut into your cornea. Then, another laser sculpts the shape your cornea is supposed to have, under that flap made by the keratome. It is a procedure that causes the least amount of pain, and the patient will regain his/her sight in a few days.
- Laser-assisted subepithelial keratomileusis (LASEK): Here, the layer of cornea that is folded back is thinner than in the case of a LASIK surgery, which minimized the chance of damage in the case of an eye injury.
- Photorefractive keratectomy (PRK): Finally, in this type of surgery, the doctor takes out the outer layer of the cornea and uses a laser to change its curvature by removing part of it. This can be one of the most painful eye procedures for astigmatism, and the patient will recover his/her vision in about a month.
Astigmatism Summed up
If you have discovered that you have astigmatism, there’s nothing to be fearful about. We hope our guide has convinced you that this fairly common and normal eye condition can be easily treated either by wearing corrective lenses, or by having surgery. No matter what option seems like the best to you, it is important to consult an ophthalmologist who will advise you on the best way to proceed, according to the severity of the condition.