Headaches are common and can be caused by many factors working together. But if they occur frequently and are associated with blurred vision, particularly after reading from a book or a computer screen, you may have astigmatism.
It's a myth that astigmatism, an eye condition with blurred vision as its main symptom, can develop from bad habits including reading while sleeping on one side or sitting very close to the television.
When the cornea or lens of an eye is irregularly shaped, vision may become blurry or distorted.
However, according to Dr Sithichoke Nakaphongse, ophthalmologist at the Thai Red Cross Society, the condition is caused by an abnormality of either the cornea or the lens of the eye, which are responsible for focusing light rays that pass through our eyes to allow us to see clearly.
"Astigmatism is not also about our eye health," Dr Sithichoke said "The condition doesn't cause symptoms such as eye redness or eye pain and watery eyes."
The ophthalmologist explained that a normal cornea is curved perfectly round and is shaped like a football, but an individual with astigmatism tends to have a cornea that is more oval and is often shaped like a rugby ball. If the cornea doesn't curve properly, it will not be able to bend the light rays perfectly into the eyes, which means the retina at the back of the eye will not receive a sharp image.
"When the cornea has an irregular shape, the light rays will focus on multiple points on the retina, rather than just one point. So, this refractive error causes an image to appear blurry at all distances," said Dr Sithichoke.
The exact cause of astigmatism is not known. Many people were born with a cornea that doesn't curve correctly. Almost all people have astigmatism to some degree. The degree of astigmatism usually develops slowly, according to the doctor.
Some people have astigmatism only, though it's often associated with myopia and hyperopia, or far-sightedness. A survey showed that about 30% of Thai people who are near-sighted and far-sighted also have astigmatism.
People with minor astigmatism may not have significant vision problems and don't require treatment. But when the degree of the condition measures over 2.00 diopters, which is considered moderate astigmatism, correction may be needed. To detect the condition, a comprehensive eye examination that includes measuring how the eyes focus light can be performed by eye-care professionals.
People with astigmatism may experience eye strain more often when they have to focus on reading for a long periods of time, and this leads to headaches.
"They often [see a] shadowy effect on letters and difficulty seeing the fine details of them," Dr Sithichoke said "Some of them have bad squints to help them see things clearly."
People with moderate to severe cases of astigmatism that are left untreated are at risk of accidents while driving and operating machinery. This is because they are more likely to have difficulty driving at night and working under particular lighting conditions.
Astigmatism can be corrected with prescription eye glasses and contact lenses to help adjust the light rays getting into the eyes. While glasses are the simplest and safest option to correct the condition, some patients have issues with wearing them. Dr Sithichok said patients may suffer from astigmatism in varying degrees in each eye. Those who have a big difference between each eye often have difficulty wearing glasses to correct their vision.
"They often complain about having headaches when wearing them, so they may need to opt for contact lenses," he said.
Mayumi Fang, professional affairs manager of Johnson & Johnson (Thailand)'s Vision Care Division noted that contact lenses can also be a safe and effective choice to correct astigmatism when they are perfectly fitted and used correctly. There is also a specially designed contact lens that helps keep the lens in the correct position using the power of a natural blink; the lens doesn't rotate while blinking.
"Well, contact lenses generally give people with eye problems a more active and comfortable lifestyle.
"The lenses may create clearer vision. They offer a wider field of view," Mayumi said "Users need to be well aware of good lens hygiene to help reduce the risk of eye infection."
"Contact lenses are still foreign bodies to the eyes. Be careful using them," said Dr Sithichoke. "To reduce their complications, users can switch to wearing eye glasses for few days."
Laser eye surgery is also a possible treatment option for astigmatism to change the shape of the cornea. Although this surgical procedure provides a permanent correction to the shape of the cornea, the technique comes with risks.
"Patients with astigmatism should consider the pros and cons of surgical treatment. Not every patient is a good candidate for the procedure. Consult your ophthalmologist and go for the best choice that meets your visual and lifestyle needs.
"Having blurred vision may not always mean that you have astigmatism, but it can be a sign that you may need a visit to an eye-care professional to have a comprehensive eye examination," the doctor said.
