What causes sudden blindness in one eye in the dark/low light? it resolves when i turn the light on. other eye is unchanged?

This symptom needs a visit to an ophthalmologist to find the cause-soon

This dose warrant an examination by an ophthalmologist ASAP as glaucoma or optic neuritis, both serious conditions, are possibilities.

There are a number of conditions (often hereditary) that can cause decreased vision in low light. Most often, but not always, they effect both eyes. They often involve defects in the rods and cones of the retina (the most well known is retinitis pigmentosa). You should see your ophthalmologist

Please see and ophthalmologist for an evaluation asap