Lazy eye could be more encouraging. That's a great question, one I'm sure everyone would like answered. I think that it is program dependent. Talking to future residents, current programs, and looking over previous match data, a mid to upper 500 score will not disqualify you but you need to have a strong application elsewhere.
Most DO programs want to see you and meet you, so with your board score auditions are essential. If I were you I would beef up your application with great letters, research, volunteer etc. showing a strong dedication to ophtho. All programs aren't looking for brains alone, in fact I know of a couple that have said in recent past that board scores are not that important as the whole person. I would rotate at as many programs as your schedule allows (schedule these early! A number of DO programs don't go through the vsas, so you can apply right now). Can you shadow local ophthalmologists, or rotate if you have a home program before you go audition? Aside from learning from great ophthalmologists, optometrists that I know really taught me to refine my skills with the slit lamp and using a 90. And then I would read read read. Read ophthobook, read practical ophthalmology, ophthalmology made rediculously simple, AOA guide for beginning residents, and I found cataract surgery from routine to complex a practical guide, very interesting.
Have confidence in yourself but also be realistic. If this is truly your passion, you'll find a way in. Remember that most programs are really evaluating who you are as a person and your inner drive, stay humble and a lot can happen. I am in your shoes and will be auditioning this upcoming summer. Feel free to PM me. You can do it!