Astigmatism: what it is, causes, symptoms and correction

In Portugal, almost one out of five people suffer from astigmatism, a condition that causes blurred or distorted distance and near vision. Find out what it is, what symptoms to look out for and how to correct it.

Astigmatism: what is it?

Astigmatism is a common refractive eye condition that occurs when the cornea or lens (or both) have an irregular shape. In a healthy eye, the cornea and lens have a regular and uniform curvature, like the surface of a basketball. However, in people with astigmatism, these structures are curved like the back of a spoon, which refracts light to multiple points within the retina and causes blurred vision at any distance.

What are the types of astigmatism?

Astigmatism can occur in conjunction with myopia (difficulty seeing distant objects), hyperopia (difficulty seeing near objects), or even both.

Myopic astigmatism

With myopia, incoming light is focused in front of the retina, rather than directly on the retina. With myopic astigmatism, light converges on different points in front of the retina, affecting predominantly distance vision.

Hyperopic astigmatism

In this case, different points of light converge behind the retina, resulting in blurred or distorted vision. Near vision is affected more than distance vision.

Mixed astigmatism

Mixed astigmatism occurs when the cornea has an irregular curvature in different directions, causing incoming light to converge in front of and behind the retina. As a result, near and distance vision are both affected. 

What are the symptoms of astigmatism?

The symptoms of astigmatism can vary in intensity, and some people may not even have noticeable symptoms. The most common include:
• Blurred and/or distorted vision, at all distances;
• Eye fatigue, especially during activities that require prolonged visual focus, like reading or using the computer;
• Headaches, due to a sustained effort to focus;
• Double vision, in the most serious cases of astigmatism;
• Eye strain or discomfort;
• Difficulty driving at night, especially due to other cars’ headlights;
• Greater sensitivity to light or visual discomfort in brightly lit environments.

How is astigmatism diagnosed?

Astigmatism is diagnosed through a complete eye examination carried out by an ophthalmologist, to determine the condition and quality of the patient’s vision. Using some quick and painless tests, the physician is able to make a precise diagnosis during the consultation.

The most common and advanced method is corneal topography, which maps the surface of the cornea in three-dimensional details to detect irregularities associated with astigmatism. This exam is performed with a device called a topographer, which creates a colour map of the different elevations and depressions of the corneal surface. Based on the results, the ophthalmologist can determine if the patient has astigmatism, the type and severity, and prescribe the most appropriate treatment for each case.

How is astigmatism treated?

Treatment for astigmatism usually involves wearing glasses or contact lenses to compensate for the irregular shape of the cornea. In the most serious cases, or when the patient does not want to depend on lenses, surgery may be advised.

Glasses or contact lenses
For many people with astigmatism, wearing glasses or contact lenses is sufficient to correct eyesight. The lenses are prescribed specifically to compensate for the irregular shape of the cornea or lens, providing clear vision. However, this option does not cure astigmatism or prevent its progression. Lenses only help focus light correctly on the retina, but they do not alter the shape of the cornea.

Surgery
Surgery can be an option in the most severe cases of astigmatism or when patients want to reduce their dependence on lenses. The most common procedure is LASIK, where a laser is used to alter the cornea, thereby correcting its irregular shape and improving eyesight. This surgery is safe, quick and painless.

How to prevent astigmatism?

As the most common causes of astigmatism are genetic, this condition is not totally preventable. However, there are some habits that may help maintain eye health.

Regular ophthalmological follow-up
Carrying out regular eye exams is essential to monitor eye health. Astigmatism can develop without especially evident signs, therefore this vigilance can make the difference in detection and the right treatment.

Wear sunglasses
It is important to protect eyes from ultraviolet rays. Although this does not prevent astigmatism, it is an essential precaution that helps preserve eye health.

Practise good visual hygiene
Avoiding eye strain is important. Whenever possible, follow the "20-20-20" rule during activities that require prolonged visual focus. For example, when using a computer, take a break every 20 minutes to focus on an object approximately 6 metres away, for at least 20 seconds.

Take care of your eye health with Joaquim Chaves Saúde

Medical and technological advances allow us to diagnose astigmatism quickly, comfortably and effectively. Count on the experienced and specialised team at Joaquim Chaves Saúde to help you recover your vision and quality of life. Schedule your appointment now, on your personal section of our website or our app.