Astigmatism is a common, mild and generally easily treatable optical defect.
Astigmatism is defect in the vision such that it is blurred due to the incapability of the eye to focus at a point into a focused image on the retina. This can be because of an irregular curvature or toric curvature of either the cornea or the lens or both.
Astigmatism is commonly present at birth but it can occur due to an injury, scar or any kind of operation to the eye, that results into the damage of corneal surface. It can also occur as a result of anything pressing continuously on the surface of the cornea.
Astigmatism may run in families and is commonly seen in premature or low birth weight babies, this might be seen because sometimes the cornea does not get adequate time to develop appropriately.
Often problems with the corneal structure can result in astigmatism, some of which are present from birth. Probability of people suffering from Down’s syndrome is 1 in 5 in people who have astigmatism.
Astigmatism is a common refractive error that accounts for around 13% of all the refractive errors . The incidence changes with age, with increased incidence in first months of life as the curvature of cornea is very steep .
Prevalence of astigmatism varies according to the races too. It is more commonly seen in East Asian people followed by Chinese and Singaporean. It has been speculated that hereditary and nutritional factors affect the incidence of astigmatism. Other ethnic groups at high risk for astigmatism are those of Hispanic origin and the natives of Brazil  .
The cornea and the lens are the two parts of our eyes that play an important role in focusing the images. In a perfectly normal eye, both these focusing elements have a perfect smooth curvature that can be compared to the surface of a smooth ball.
The cornea or the lens with such a smooth surface curvature can bend (refract) all the light rays that enter it equally to create a sharp, focused image at the back of the eye i.e. on the retina. But in case the cornea or lens is not evenly and smoothly curved, then the light rays will be focused unevenly. This leads to a refractive error and astigmatism is the result.
Astigmatism occurs when the cornea or lens is curved more in one direction and remains normal or less curved in the other directions. Depending on the affected part you will have either corneal astigmatism, if the cornea is affected or lenticular astigmatism, if the lens is affected. Both the types of astigmatism cause blurred vision. Blurring of vision can be more in one direction that can be either diagonally, horizontally or vertically. Astigmatism can be present along with other refractive errors.
Astigmatism is generally a stable condition. It can be corrected using eyeglasses, contact lenses or refractive surgery. Occasionally, astigmatism can be the result of other medical conditions, especially those causing inflammation of the eyelids.
Astigmatism can worsen over a period of time and can lead to a condition known as keratoconus. Keratoconus affects the cornea such that it becomes progressively thinner in one area and starts bulging out. These conditions need more precise treatment and more supervision by a doctor than simple astigmatism.
The first symptom of astigmatism is a complaint of blurred vision. People generally complain of double vision that affects only a single eye. Few of them suffering from astigmatism develop eyestrain, squinting and even migraine headaches  as a result of straining to focus on objects.
In children who are born with astigmatism, it remains undiagnosed till the time they start attending school or they learn to read. Some people complain of difficulty in seeing one colour in contrast with another or can have distorted images like they see that the lines lean on one side. Severe astigmatism can also lead to double vision.
The ophthalmologists and optometrists use various tests to diagnose astigmatism and to determine the amount and axis of deviation in the optic curvature.
Vision test: A Snellen’s or Jaeger’s chart or other eye charts are used to determine the visual acuity. One is asked to read from these charts to determine the visual acuity.
Test to determine the curvature of your cornea: A keratometer is used to identify which are the flattest/steepest curvatures of the anterior corneal surface. A keratometer measures the light reflected off from the surface of the cornea. This test is called keratometry. Another test called Corneal topography may also be performed to obtain more accurate measurements of the variations in corneal surface curvature.
Test to measure light focus: In order to know how the eyes focus light, the physician places various lenses in front of the eyes by using a device called a phoropter. Using Jackson cross cylinders in a phoropter helps in measuring the refractive error of the eyes   .
The physician can also use a retinoscope that will help to know how the eye focuses light. Here, a ray of light is focused on the retina and recordings are obtained regarding how the retina focused on the light beam.
Astigmatism can be corrected with the help of eyeglasses, contact lenses, or refractive surgery. Main objective of the treatment is to correct the uneven surface curvature of the lens/cornea that's leading to the blurred vision and improve the vision.
Refractive surgeries. This treatment method corrects the problem by modifying the surface of the eye. These surgical methods are as follows:
Astigmatism cannot be prevented. It runs in families and many a times present from birth. Chances of astigmatism can be reduced by taking optimal measures of eye safety while playing sports.
Astigmatism is a refractive error affecting the eyes. It is generally present from the time of birth or can be acquired later in life. Often injury to the lens or cornea or repeated infections of the eyes can lead to this condition. Astigmatism can affect both children and adults.
Those suffering from slight astigmatism won’t see much change in their vision. Thus, each child must have regular eye checkups to detect any eye abnormality at its earliest and intervene aggressively. Since it cannot be prevented, prompt treatment of the condition once diagnosed helps in preventing it from worsening.
Blurring of vision is the commonest symptom of astigmatism. There are various treatment options that are available to correct this condition. Selecting the best treatment depends on the condition of your eyes, the refractive status and your lifestyle requirements.