9 month old doesn't crawl on all 4's, sit up or stand. Should I ask a doctor?

He is far sighted and is supposed to wear gles (his prescription is +3.50 in each eye) and he has occular albinism. He can scoot across the floor pretty well on his belly. He doesn't show any interest in sitting up or standing at all. I was wondering if I should ask his doctor about this. He refuses to keep his gles on. I think the main problem with that is because he has metal frames and they're uncomfortable for him. Could his farsightedness play a part in this?