I know that. But technically, optometrists have a "professional doctorate" in optometry ("doctor of optometry" or OD), just like doctors have a "professional doctorate" in medicine ("doctor in medicine" or MD). Neither MDs nor ODs are traditional doctors, which is what you would traditionally call someone with a PhD, and not someone who takes care of your health.

I just don't happen to know any ophtalmologists, or anyone with a PhD who specializes in this, and in any case a good optometrist has overlapping expertise and concerns with ophtalmology and current research. Take it for what it's worth, no more, no less.