First of all, you need to know how serious his astigmatism is. Astigmatism is due to the refractive error which results from the shape of the eye not being round enough. Nearly every one has astigmatism to some extent. If the situation is not so serious that his vision has been affected, you can just leave it alone. However, if the situation is not so optimistic, you have two options.
1.Get prescription corrective lens for your child, whether eyeglasses or contact lenses. You doctor will choose what the most suitable is for him.
2.Let your child wear eyewear to correct his vision until he come of age. When his eyes has grown well, you can take him to have laser surgery to change to shape of his cornea and cure his astigmatism.
Apart from the two treatment, you can also prevent his vision from getting worse through the following precautions:
1.Have his vision checked regularly.
2.Teach him to read, watch TV, use computer, or play iphone in right position and distance.
3.Adjust the lighting of your house so that his vision won't be harmed.
4.Add food rich in vitamin A into your recipe.