I always wear eyes, and ears for that matter. Probably because I got out of high school and went straight into machining.
I don't bother buying sunglasses anymore, I buy smoked safety glasses at Northern Tool, cost about three bucks. Clear ones cost about two. Protection is cheap, eyes are not...
I've took my safety glasses off to find sawdust, grass, burnt power, etc, all over the lenses. I've had rust or oil from underside of a vehicle fall into my eyes enough that I don't go under a car without glasses on.
IMO, the only downside to safety glasses that they only seem to fog up when you really need them to be clear...
If you work in manufacturing, your company may cover the cost of your prescription safety glassed 100%. The company I work for used to, I don't know of they still do.