I always wondered what ophthalmologists see inside someone's eye and what they're looking for. The whole thing is a mystery to me. Are there any photos of what the eye of a patient looks like from the doctor's point of view?
The name of the instrument is ophthalmoscope. It is used to determine the health status of your retina. Retina is the one of the few places in the body where you can observe the blood vessels directly.
The link also includes a picture of what your eye looks like from doctor's point of view.
They look at retina. Google for it. The look of retina can evident of some diseases. This is the subject of medical education.