Astigmatism may be the result of an eye injury, disease or surgery, according to Mayo Clinic. Some people may have astigmatism present at birth. Despite speculation, squinting, reading in dim light or sitting too close to a television screen do not cause or worsen astigmatism.
Astigmatism occurs when the lens or cornea of the eye curves more steeply in one particular direction, notes Mayo Clinic. Doctors refer to one type as corneal astigmatism, and the other is lenticular astigmatism. Both types of astigmatism may cause blurry vision that may be especially prevalent horizontally, vertically or diagonally.
Other refractive errors, such as nearsightedness and farsightedness, may occur in conjunction with astigmatism, explains Mayo Clinic. Symptoms of astigmatism include blurred or distorted vision, eyestrain and headaches. It is important to set an appointment with an eye doctor if vision problems make it difficult to perform or enjoy standard daily activities.
People with astigmatism may need to have eye checkups more often than those who do not, reports Mayo Clinic. Until the age of 55, adults over the age of 40 should see eye doctors for exams every two to four years. Adults over the age of 55 should have their eyes checked every one to three years. People over the age of 65 should have eye inspections every one to two years.