Hey Rick, keep the faith man! My 24 year old daughter had Thyroid cancer last year... I felt the same way. Shock, disbelief, denial, but most of all I was just plain scared.
She is now doing fine and in total remission.
I know nothing of cancer of the eye, but early detection and treatment is a good thing (plus the brain is a very powerful organ, as already said keep a positive outlook as much as possible). You will be in my prayers, hang in their buddy, and as Devil said let your family know, this is no thing to go through alone. I know that I would have been more upset if my daughter had kept me in the dark even for a few days.