As an extremely tall teacher, I don't want you face level with my crotch. The chances of me sharing information with you that only you need to know is extremely high. I need to get close to avoid disrupting class. If a teacher in invading your personal space, you need to make sure you tell them... but bending down or kneeling isn't a blind thing. It's just what I do because I'm tall.

Many years ago, I taught in a small Christian school for three years. I always got down on my student’s level. I wanted them to feel like they had my personal attention.

Their leaning over/kneeling isn't necessarily due to your visual impairment. It's typically a way for the teacher to not be towering over any student they work with. Makes it more personable when y'all are talking and reduces the distance of "lording/ruling" over the students. I hate being taller than someone when they're sitting (or if I'm working with really little kids) so I lean down/kneel/sit on a nearby chair so we can have a conversation as equals.

It may be that you can see a little so they want to make sure that you can see their face as they communicate with you. Next time, invite them to pull over a chair so that the teacher may sit down on the other side of the desk.

It sounds condescending to me.

Maybe you could ask them not to do that?