How many different types of astigmatism?

[Boothville]

I just want to know the types of astigmatism. Is somebody know?

[Boothwyn]

Astigmatism can be divided into two types, regular astigmatism and irregular astigmatism. Regular astigmatism means that the principal meridians are perpendicular to each other. While irregular astigmatism means that the principal meridians are not perpendicular. Most astigmatism is regular corneal astigmatism, which is caused by the misshaped cornea.