Bradley:I'll follow on from what Mark said, by adding that the only thing that involves contact is "Push hands", and that involves contact only on the hands and arms. Wearing glasses is not a hinderance. The worst thats going to happen is that you lose balance and either fall over or are pushed over from a standing possition.
The whole thing can take on a very deep spiritual level, from the "warm up", "Qigong", "Tai Chi form", to the "push hands" (though some teach the individual martial applications, too). These are all elements of the art known as Tai Chi. There are no gradings because it's a lifelong thing (though I understand that some American dojos use a sash system ).
I took it up a little ove a year ago and within about six months I had memorised the whole form (there are only two in the style that I do - "Long Form" and "Cannon Fist", though portions of these may be used as short forms). I've continued to refine and refine, but to be honest the Form is only a mechanism. LIke in Aikido, which Paul discussed, it's mainly about manipulating Qi (or Kia, in Japanese, since Qi and Tai Chi are Chinese).
LIke Mark, I felt "drawn" to it for some time. When an instructor was needed one suddenly appeared. For a small island of population 21,000 that was a minor miracle in itself. I now assist the instructor with teaching, and hope to make that step into the additional Cannon Fist form, next year. To be honest I've not found the continual learning of the single form onerous. There is always something to learn about Qi, your body (be it dynamics or physiology), or the universe you are part of.
Philosophically it's very much rooted in Tao, but I've had no difficulty assimilating it into Zen / Christian perspective. Philosophies dissolve into reality, when you get into the depths of that kind of work.
As one "master" put it: You can master the true essence of Tai Chi in twenty years, or a single year. Some people just "get it", whilst for others it can be a lifetimes journey. Regardless, it is a journey that lasts a lifetime anyhow, as you enjoy eternity in a grain of sand...
Have you the patience and discipline grasshopper?