Astigmatism might be the most common yet misunderstood of all vision problems. Most people have some degree of this disorder, and it is caused by an irregularly shaped cornea. Instead of the cornea having round shape (like a baseball) it is shaped more like a football, with one meridian being significantly more curved than the meridian perpendicular to it (Source: All About Vision).
So what are meridians? The best way to understand meridians is to think of the front of the eye like a clock. If you made a line between 12 and 6 as one meridian, and a line connecting 3 and 9 is another. Eyes with the steepest and flattest meridians with astigmatism are called principal meridians.
Sometimes, astigmatism is caused by the shape of the lens inside the eye. This type of astigmatism is called lenticular astigmatism, different from the more common corneal astigmatism.
There are several types of astigmatism, but the three most common include:
- Myopic– One or both principal meridians of the eye are near sighted. Should both the meridians be nearsighted, they are myopic in differing degree.
- Hyperopic– One or both principal meridians are farsighted. Should both the meridians be farsighted, they are hyperopic in differing degree.
- Mixed– One principal meridian is nearsighted and the other is farsighted.
Astigmatism often occurs early in life, so it important to schedule your little one for an eye exam to offset vision problems in school from uncorrected astigmatism. Symptoms of astigmatism include eye strain and headaches, especially after reading.