@cpitts Were you having vision issues, or was this a routine visit? My docs made sure I knew exactly the symptoms to watch for, to stop ethambutol immediately if noticed, and I had my eyes screened every 3 months while on the meds (incl 6 Mos every day). I'm still fine over 6 years later. There are other docs who prescribe alternative meds, but an ID doc should determine whether your strain of MAC is sensitive to one of them.
PS, my ophthalmologist was the doc of choice to see MAC patients in out clinic system.
I would ask my doc to explain why they felt you were at extraordinary risk and should not use ethambutol- like seeing changes.