No, don't use face primer as an eye primer. It may or may not be safe (it would depend on the product), but the goal of a face primer is to smooth your skin so products glide on and look flawless. An eye primer is definitely safe to use around your eyes since it's created specifically for that, and the finish will be ideal for grabbing onto your powder eyeshadows and intensifying the color. Under the eyes, use face primer (for your concealer), unless it's right at the lower lash line, where you're applying more eyeshadow. In that case, "line" your eyes with a bit of the eye primer, too.