You do not have double vision. true double vision means you see two of everything with both eyes open. When you shut one eye you do not see double. Double vision is a 2 eye problem. What you are describing that you see with one eye is called 'ghosting" it is a one eye problem. there are many causes the most common are: needing glasses especially for astigmatism, glasses that are incorrect or poorly fit, cornea disease, CATARACTS, and macular disease. You need to see an eye MD ophthalmologist and have complete medical eye exam, possibly with cornea topography and macular OCT. Why you see in dim light is usually due to the larger pupil size in dim light.