There are many types of vision loss. Unfortunately, most of them are not reversible, but a few are. However, it is very important that you see your neuro-ophthalmologist because even the irreversible causes of vision loss have treatments that can slow their progression. And furthermore, your vision loss could just be one part of a broader disease, that could be affecting the brain, bone, or any part of the rest of the body.
The type of vision loss you most likely have will depend on your age, what other medical illnesses you have, whether your vision loss in in one eye or both eyes, or on one side of your body or the other side of your body. The rapidity at which the vision loss set on will also affect the diagnosis your neuro-ophthalmologist makes. This diagnosis will ultimately based on a slit lamp exam (an examination where a large, sophisticated camera shines into your eye to allow him/her to look at the back of your eye), visual field testing (a machine that helps to detect what parts of your vision are deteriorating the most), and visual acuity testing (a test to see how sharp your vision is).