Astigmatism is one of the most common vision problems. It affects 26% of the population and is the third most common visual problem among the Spanish, only behind myopia (28%) and presbyopia or eyestrain (28%). According to experts Optics Rome, astigmatism often associated to any of the visual defects such as myopia or hyperopia. To get an idea, 13% of the population has only this problem, and there is another 20% who have it associated with myopia or hyperopia.
What is astigmatism?
Astigmatism is an imperfection in the curvature of the cornea (the clear dome that covers the iris and pupil of the eye), or the structure of the (crystalline) lens of the eye. Typically, the cornea and lens are smooth and curved equally in all directions, which helps focus light rays and are correctly pronounced towards the retina at the back of the eye. However, if the cornea or lens are not evenly curved or soft, light rays are not refracted correctly. This is called a refractive error.
When the cornea has an irregular shape, the condition is called corneal astigmatism. When the shape of the lens is distorted, the condition is called lenticular astigmatism. As a result of any of these types, near or distant vision becomes blurred or distorted. It’s like looking in a mirror in a funhouse where you look too tall, too wide or too thin.
You may be born with it. In fact, most people probably born with some degree of it, and have that together with other refractive errors: myopia or hyperopia.
While adults with a higher degree of astigmatism can realise that their vision is not as good as it should be, children who have symptoms may not be aware of the presence of the condition, and you probably do not complain about having blurred or distorted vision. But if it is not corrected it can seriously affect a child’s ability to perform well in school and sports. It is therefore essential that children have eye exams regularly in order to detect the presence of astigmatism, or other vision problems as soon as possible.
What Causes Astigmatism?
Astigmatism is caused by an irregular curvature of the cornea or lens. If the cornea or lens are not smooth and its curvature is uneven, light rays are not refracted properly. This is called a refractive error. It is a type of refractive error that causes blurred or distorted vision near and far distances.
Astigmatism is very common. In most cases, people with it are born with this condition. The reason that the shape of the cornea is different from person to person is unknown, but likely to develop it is inherited.
Sometimes it can develop after an injury, disease, or eye surgery. It is a myth that the astigmatism will develop or worsen due to activities such as reading in low light, or sitting close to the television.
Symptoms of Astigmatism
Symptoms may include blurred vision, distorted vision areas, eyestrain, headaches, squinting to try to see things clearly, or eye discomfort.
Patients with astigmatism have blurred vision, they do not distinguish fine details and perceive the distorted figures, both near and far. As a result of this incorrect view, they can suffer headaches or dizziness, and force the eye muscles to try to correct the defect. This artificial accommodation, however, ends up failing due to eyestrain it causes, and the astigmatic will again see blurred objects.
The patient may also experience other visual discomfort as redness, hypersensitivity to light, or double vision. Symptoms can vary depending on the level that is suffered blurred vision, graduation and age of the victim. Likewise, if the defect appears associated with other problems such as nearsightedness or farsightedness, it is more common than visual fatigue, itching and redness, and even dizziness or headache feel.
Your ophthalmologist will perform a thorough eye exam, and will use various instruments to measure how your eye focuses light.
They will measure your visual acuity, asking you to read the letters in a box away, and determine the clarity of vision at a distance. The control or power of focus will also be examined with a series of lenses placed in front of your eyes.
The curvature of the cornea is measured with a keratometer. Corneal topography can be used to provide additional information about the surface shape of the cornea.
With these tests, your doctor can diagnose astigmatism and may determine the degree of prescription glasses or contact lenses that you need to have a clear vision. Other treatment options will also be discussed, such as surgery.
How can it be prevented?
It cannot be prevented but can be diagnosed by a common eye examination including refraction test and / or corneal topography.
Certain special cases may require more complex or other evidence.
Usually a mild to moderate astigmatism can be corrected with glasses or contact lenses.
In the past, contact lenses for astigmatism could only be rigid lenses (RGP or GP lenses for its acronym in English), but this is no longer the case. Now you can use a soft lenses called toric contact lens. However, although toric contact lenses may be suitable for some people, if you have a severe astigmatism, a rigid contact lenses or a pair of spectacles may be a better option. Your eye doctor will explain your options for lenses.
For some people, surgery may be an option for vision correction, including LASIK. Your eye doctor can discuss with you the different types of refractive surgery procedures that can be considered for the correction of astigmatism.