Oct and iop concerns. Both the eyes?

Hello doctors 1. When OCT of the macula is done. It only shows information about the retina or does it also show the status/health of the optic nerve to detect any damage from the high eye pressure. 2.I have seen when doctors do dilated exam, they shine light more into the right eye to check structures behind the eye. Is optic nerve located behind the right eye and not left eye? We as humans have 2 retinas behind each eye or just one retina covering across both the eyes? 3. Do drainage canals of each eye work separately or in conjunction with each other. I mean, do they affect each other or not. My left eye reports High pressure but right eye reports normal eye pressure. Does high pressure in left still poses risk for glaucoma..or its the right eye which is more important for any damage behind eye. Thank you for the patience and time to read this. Response awaited.