Go for it! I'm 50 and not stopping. I working on flying through the prereq's, many of which I took many years ago. And, taking the OAT in December in an attempt to get into the Fall 2010 class.
I shadow with an optometrist and ophthalmologist and they both say we're (people like you and I) are making a great decision. Both realize that I'm doing this to help people and they really respect me for that. So much that they have integrated me into their team.
This isn't about "making money" or anything like that. It's about being a primary healthcare provider and helping people; always keep that in mind. Patients will entrust their visual system healthcare decisions with you. A true professional never does anything purely for money. When I talk to the adcoms at the various schools, they know that's what it's with me. They know that older applicants may not be as young and bright-eyed (no pun) as the majority of the applicants. But they know the older students bring maturity, experience, dedication, and most importantly, leadership.
Also, they know that you are giving up a lot. It's not easy making the change, and from my discussions with them, they really respect that. I gave up a really high paying job, sold the bimmer, selling the house to move into a much smaller apartment, and going to school full time. So, my life has really been rearranged for this. But, I'm doing this to help people, and I haven't felt better in my life about any decision!
Just study hard, get those grades, and score high on the OAT. If you haven't, start shadowing NOW. There's no substitute.