In my opinion, it would not really benefit you more than any other Rec you can get.
It's not a dentistry related so it would not be able to show how much experience/passion you showed about dentistry.
I would make sure to get LORs from someone that knows you well. A well-written LOR from someone that really knows you will help you way more than just a random doctor (I'm not sure how much of relationship you had with this opthamologist considering that you're applying to dental school).
If it was done while you were considering pre-med or something, then it is definitely not going to help you other than being just a LOR, and may even hurt you if the doc somehow mentions your passion for medicine or field of opthamology.
Remember, many schools do limit on numbers of LORs and they also do have requirements on their LORs (certain course professor / dentist, etc.). Make sure you have at least 2 science profs and a dentist before trying to use this LOR.