Nyctalopia (Night Blindness) not be cured by wearing glasses. That's why taking vitamin A can prevent Nyctalopia (Night Blindness). In the normal eye there is a known pigment called visual rodopsinatau puple. Pigment contains vitamin A which bound to the protein. If the eye receives the light, there will be a conversion of rhodopsin into visual yellow and visual white then. At conversion, the required vitamin A.
While the regeneration of visual purple will only occur when the available vitamin A. Without regeneration, the vision in dim light, after the eye receiving the light will be disrupted. If there is a deficiency of vitamin A, the initial symptom is the occurrence of Nyctalopia (Night Blindness). That is, the eye will be impaired when switching from a lot of light into dark places. It makes Nyctalopia (Night Blindness) only happen when the sun begins to set.
Active form of vitamin A, some form of retinoic acid which will play a role in gene expression. In the retina of the eye, retinol is converted into 11-cis retinal are able to conjugate dehida with opsin to form rhodopsin is involved in the process of vision. Thus, the eye is in desperate need of the presence of vitamin A.