An opthamologist is an MD, an optometrist is not. Normally at Sears, Walmart, the place in the mall, you'll find an optometrist. Which is just fine as long as your eyes aren't really bad or you have something serious going on. I'm assuming since you're in your 40s and have never been, there is probably no probs, and any vision issues are probably age related. I have had glasses since I was 5 (think Coke-bottle lenses) and my eyes are so bad I have to see an opthamologist. Opthamologists will also do eye surgery. And they are also more expensive, in general. However, because they are an MD your medical ins may cover the visit, but not the glasses. Which can be helpful if you don't have vision ins.
Nan