Let's start off with Astigmatism isn't a disease it is part of a glasses prescription. Astigmatism is normally caused by the cornea (front surface of your eye) not being perfectly round where one part is stronger/steeper than the other part of the cornea. What that does is make half of the image in focus and the other half out of focus. Depending on where the astigmatism is located on the cornea it would make the horizontal part of the object or letter blurry and the vertical part of the object in focus (see picture below).
This also causes shadows on letters and also the lights to be streaks instead of circles (some can be due to Higher order aberration/nature glare of your eye).
If it really bad it can cause one-eyed double vision. Trust Dr. Chappel he has a lot of astigmatisms when he takes off his glasses/contact he can see 4 objects sometimes. Some things to help besides having the best glasses prescription as possible is having an anti-glare/anti-reflective coating. Astigmatism should never stop you from wearing Contact Lenses. If needed we can always order specialty soft contact lenses or if you want the best vision possible you can go into specialty contact lens like Sclerals contact lens (what Dr. Chappel wears).