Astigmatism is caused by a lens or cornea that does not smooth cause light into the eye, become unfocused when forwarded to the retina. Therefore, the resulting view becomes opaque.
Based on the location of the damage, astigmatism can be divided into 2 types. Astigmatism caused by a defect in the cornea of the eye is called corneal astigmatism, while caused by a defect in the lens of the eye is called lenticular astigmatism.
While based on the type of damage, there are two types of astigmatism, namely regular and irregular. Regular astigmatism is when one side of the cornea is more curved than the other. This condition is the most common condition and can be treated with the help of glasses or eyepiece. Irregular astigmatism is when the cornea of the eye is uneven not only on one side, but on the entire surface of the cornea. This condition is generally triggered by an injury that leaves a wound to the cornea. This condition can be treated with the help of contact lens, but not with glasses.
The case of astigmatism generally arises from birth, although the exact cause of why this condition appears is still unknown. There is an assumption that astigmatism is hereditary in the family. This condition is also more common in infants of low birth weight or premature birth.
Some of the causes that can cause astigmatism:
- Complications due to eye surgery.
- Injury to the cornea due to infection.
- Conditions on the eyelids that interfere with the structure of the cornea. For example there is a lump on the eyelid that suppress the cornea.
- Keratoconus and keratoglobus, conditions in which the cornea may change shape, either bulging or thinning.
- Other eye conditions that affect the cornea or lens.
Myopic (hypermetrophic / hyperopia) or myopia (myopia) may accompany astigmatism.