I just posted a long article about the Definition of Astigmatism. What's amazing is the history of it. I had no idea where it came from... for how long people were describing the symptoms of astigmatism... and that an astronomer came up with the first lens to correct it... It's amazing that it wasn't eye doctors coming up with glasses and lenses... makes you wonder what "eye specialists" really specialize in... prescribing crutches? The biggest specialty - fashion advice. Profession - selling the damn things... it's mind boggling that physicists and astronomers came up with the most popular tool to correct eyesight... Anyways, you can check it out here. It's a good read.