Dr. Hibberd’s answer:

 

Cone dystrophies are generally genetically inherited conditions caused by pigment deposition on the retinas. This results in varying degrees of progressive vision loss. People with the condition may first suffer blurred vision, followed by a sensitivity to light, and then night blindness.

Sometimes it can cause other problems, as well. Unfortunately, no therapy will restore vision or stop the progression of the disorder. Treatment generally involves managing complications and trying to slow down the progression to vision loss.

Any supplementation should be done only under the guidance of your ophthalmologist, since vitamin A, while necessary for night vision, can be harmful and toxic to the retina when taken in excess.