Astigmatism - A Guide
What is astigmatism?
Astigmatism is characterized by abnormalities in the curvature of your eyes. This can cause your vision to blur. It is mild and it can be treated easily.
The front surface of your eye is called the cornea. The inside of your eye is referred to as the lens. When the inside of your eye has a difference curvature from this front surface, there will be astigmatism. The surface of your eye should be smooth but with astigmatism, there will be some areas that are flatter and some areas that are steeper.
There are two types of astigmatism based on the affected part and either of them can blur your vision. If your cornea is distorted then you have corneal astigmatism. If your lens is distorted then you have lenticular astigmatism.
Your vision can be blurred at several distances. You can experience astigmatism when you are born, in combination with nearsightedness or in combination with farsightedness. Astigmatism does not usually get worse or get better but remains the same over time. People who are very bothered with their astigmatism can go through corrective surgery or can use corrective lenses. If you aren’t bothered with your astigmatism then you can opt not to have it treated at all.
What are some of the symptoms of Astigmatism?
Listed below are some of the symptoms of astigmatism:
- vertical lines, horizontal lines, and diagonal lines will appear blurred
- strained eyes
- distortion in areas of your visual field
What are the causes of astigmatism?
There are two parts in your eyes that are used to focus images. These parts are the lens and the cornea. If your eye is shaped perfectly then these two parts smoothly touch each other. This smooth curvature will bend and refract incoming light in the same way and it will generate a sharp, focused image at the back of your eye. The back of your eye is referred to as the retina.
If your eye is not shaped perfectly, meaning, if the cornea and the lens do not touch each other as smoothly as possible then the light rays will not reflect perfectly. Refraction errors will result in astigmatism.
What are the two different types of astigmatism?
The shape of the cornea or the lens determines the kind of astigmatism that affects you.
1. In regular astigmatism, both sides of the oval shape of the cornea are the same. This means that the curvature of the cornea or the lens is equal all over.
2. In irregular astigmatism, the sides of the oval shape of the cornea are not the same which results in different curvature for the lens or cornea all over.
Chalazion and keratoconus are two eye conditions that can trigger astigmatism. Chalazion is characterized by a lump that develops inside your eyelid. This is caused by a blocked gland. The blocked gland will change its shape and it will eventually put pressure on the cornea. The cornea will become irregular in shape and it will result in astigmatism. Keratoconus is characterized by the thinning and bulging of your cornea. Again, the uneven shape will result in astigmatism. These conditions are rare in individuals.
In some cases, you can get an eye injury from surgery. For instance, if your cornea becomes infected then there will be scars. When your cornea is scarred, there will be a change in the way light enters your eye. The focus on the retina will be altered and distorted and thus result in astigmatism. This kind of astigmatism is not permanent and will return to normal when the cornea has healed. Laser eye surgery may not involve any stitches but if it does then the shape of your cornea will be altered and thus result in astigmatism. When the stitches are removed and when the cornea heals, the astigmatism will eventually go away.
There are other ways where astigmatism can happen. They can occur with other refractive illnesses like the myopia or hyperopia. Myopia is also known as nearsightedness. When your eye is too long or when your cornea is too curved then the focusing of light on your retina will not be sharp. This will result in a blurry appearance for objects that are far from you.
On the other hand, there is hyperopia which is also known as farsightedness. When your cornea is not curved enough or if your eye is shorter than normal then the light will be too focused at the back of your eye. This will make objects that are close to you look blurry.
When do you need to see a doctor?
You should see an eye doctor or an ophthalmologist if the quality of your vision is already affecting the way you perform your day to day tasks. If your vision is affecting the way you enjoy your life then you should get medical attention right away. Your ophthalmologist will find out how severe your astigmatism is. You will be given advice on how to correct your vision.
Healthy adults should have their eyes examined every two to four years until they reach the retirement age of sixty five. During your senior years, have your eyes checked every year or every other year so that you can monitor any signs of illnesses. People with astigmatism have to go to the eye doctor more frequently than the regular healthy adult.
In many cases, people are born with astigmatism. It can develop after injuries to the eye or when a disease occurs. If you read in poor lighting conditions, sit too close to the television, or if you squint then you should not be worried if it affects your astigmatism.
How will the ophthalmologist diagnose astigmatism?
Here are some of the tools that your ophthalmologist may use to diagnose your astigmatism.
- Keratometer – This is an instrument that measures that amount of reflected light from the surface of your cornea. Your ophthalmologist will be able to determine the severity and the orientation of your corneal astigmatism using this instrument.
- Keratoscope – It is an instrument that measures the severity of corneal curvature by projecting light to the cornea. The way the light reflects on the cornea will determine the severity of the astigmatism.
- Videokeratoscope – If a keratoscope is fitted with a video camera then the device is turned into a videokeratoscope. Using corneal topography, the ophthalmologist will be able to identify the changes in corneal surface curvature and identify the severity of the astigmatism.
How can astigmatism be treated?
Treating astigmatism is all about addressing the uneven curvature that causes your vision to blur. You can go through refractive surgery or you can simply wear contact lenses in order to address the illness. Here is a list of ways to treat astigmatism
- Contact Lenses – You can correct either lenticular or corneal astigmatism through the use of contact lenses. There are so many contact lenses available in the market nowadays. You can purchase contact lenses that are soft, hard, disposable, permeable, bifocal, and many more. Weigh out the advantages and the disadvantages of the several types of contact lenses before you purchase them so that you make a good choice
- Corrective Lenses – You can wear corrective lenses in order to counteract the irregular curvature of your cornea
- Glasses – You can also wear eyeglasses to counteract the irregular curvature of your cornea. Like contact lenses, glasses come in a variety of shapes, sizes, styles, and functions
- Orthokeratology – This procedure is also known as Ortho-K. This procedure requires you to wear a rigid set of contact lenses for several hours in order to improve the curvature of your eyes. The number of hours is reduced gradually until your eye takes its new shape. If the procedure is stopped midway then your eye will simply return to its previous state
- Corneal Transplant – If you can find healthy donor cornea then you can simply replace yours. The procedure will be performed under local anaesthetic or general anaesthetic, depending on your ophthalmologist’s recommendation and your choice
- New Lens Implants – You can also implant corrective lens in your eye although this is a rare procedure
- Radial Keratotomy – This is an old procedure and is not usually performed anymore. Initially, there will be good results although farsightedness has been reported to develop in some patients
Refractive Eye Surgery used to treat astigmatism
Reshaping the surface of the eye is an effective way of correcting astigmatism. Here are some of the refractive surgery methods
- Photorefractive Keratectomy – This is abbreviated as PRK. In this type of surgery, the outer protective layer of your cornea is removed. Afterwards, a laser is used to correct the curvature of your cornea.
- Laser-assisted subepithelial keratomileusis – This is abbreviated as LASEK. In this kind of surgery, a thin layer of cornea is folded back. This is done so that the eye will not incur as much damage compared to a complete exposure. If you are into sports or if you are in danger of injuring your eyes then this kind of surgery is a better option for you.
- Laser-assisted in-situ keratomileusis – This is abbreviated as LASIK. In this procedure, the doctor will make a thin circular hinged cut into your cornea by using a special instrument called a keratome. A laser can also be used to make this kind of cut. The surgeon will lift the flap and then use an excimer laser to sculpt the shape of the cornea underneath the flap. An excimer laser is a type of laser that does not produce heat and it is ideal for this kind of surgery.