Night Blindness is a genetic disorder in which the sufferer has trouble seeing at night. Two things cause this disorder in general. The first cause is a lack of vitamin A which helps develop the retina and vision receptor cells. Vision receptor cells consist of cones and rods, cones for bright light and rods for less light. When there is a vitamin A deficiency, the rod cells don't develop properly. The second cause is a genetic inheritance.
Night blindness is a sex-linked disorder because the X-chromosome was found to be different than normal in people with the disorder. There are many vision-related effects this disorder can have on a person. In most cases, the person isn't completely blind in dark areas, but sees things a lot darker than they really are. In other cases, it takes the person's eyes much longer than normal to adjust to different light settings. For example, if a person with night blindness suddenly has the lights turned off in front of them, it may be up to 10 minutes before they can see anything at all. Also, the same thing happens when going from dark to light.
The sufferer will see extremely bright images when flooded with light after having adjusted their eyes to darkness. There are many treatments for night blindness that exist today. The most common treatment is taking vitamin A supplements to restore the vitamin A that helps develop and maintain the retina. Also, zinc supplements can be taken as well to further strengthen the retina. Physical forms of treatment include lasers, freezing, injection of gas into the eye, scleral buckling, and removal of the gel inside the eye.
This disorder is usually accompanied by myopia (nearsighted). About half of teenagers with myopia will develop some form of night blindness. These cases start out around the age of fifteen. Also, about 52% of women said they had trouble seeing at night during their last pregnancy. During pregnancy is usually the only time a woman will experience the disorder. It was recently discovered that a gene called NYX is the gene that causes the genetic form of night blindness.
This gene is located on the X chromosome. Since men only have one X chromosome, and women have a second X chromosome that can cancel out the bad gene, men are much more likely to have it than women are.