When a flash photo of a human being is taken, the light will reflect from their eyes in such a way as to cause "red eye." In a child with an eye tumor, the light will reflect back like a cat's. This "white reflection" is known as "white reflex." It can be a sign of several serious health conditions in children and usually is first diagnosed through photos.
In photographs without red eye, the light from a camera flash will usually show up as a tiny white dot. This is because there is a tiny area in the back of the human eye where there is no cones or veins to absorb light. By contrast, cats have a membrane in the back of their eyes called the tapetum lucidum, which reflects light as white. If an eye tumor is present in a human eye, it will reflect all of the flash and create the glowing eye effect usually only seen in photos of cats.
Since white reflex is usually first diagnosed from photographs, it is important that parents of young children take a monthly photo of them in low light with a flash. Since the size and shape of the tumor may make it so that the white reflex won't show up from all angles, it's important that photos of the baby's face are taken from many different positions. White reflex can show up in one eye or both eyes.
Another way to make sure white reflex is diagnosed early is simply to have regular visits to the eye doctor. At these visits, the optometrist will shine a small light into the child's eyes. This will have the same effect on the eye as a photographer's flash and will help to diagnose if everything is normal.
It is important for a parent to take their child to the doctor upon finding an instance of white reflex in photos taken of them. It can be a sign of many different conditions, from oncoming blindness to eye cancer. Diagnosing a child for eye problems can be difficult, since small children and babies are often frightened by doctor's visits and have trouble holding still. Sedation may be needed in order for the eye to be examined. Afterwards, surgery may be needed in order to fix the eye problem.
White reflex can also show up in photos of adults. It is not usually a sign of cancers, but it can be a result of cataracts. Adults should also go to an optometrist as soon as possible in order to have their eye problem diagnosed.