Yes it is possible. There are DO ophthalmology residency programs and DO Physicians also apply and match to allopathic residency programs. The difficulty is that you have a much smaller pool of available residencies to choose from. Ophtho is already a very competitive field. This year there were approx 430 available allopathic spots and the match rate for US Seniors was about 75% or so. There are about 110 or so allopathic residencies in the country, but you will not be looked at by 2/3 of them because you are DO. That said, I personally went on 15 interviews at a range of programs and a few lower tier programs had DO physicians on staff.
You will need exceptional grades, have to take both the comlex and the step exams and score very well, and research is a big plus. Its not impossible, but certainly its an uphill battle.