It has long been known that the way your eyes look in a photo can tell you a lot about your health.
This is because the light from the flash reflects off the color of the retina at the back of the eye, which converts images into electrical signals sent to the brain.
Doctors have warned that if one or both pupils are bright white, it could mean there is not enough blood in the retina. And this problem can signal a range of conditions – from common cataracts to life-threatening eye cancer.
But now experts have indicated that a selfie taken with a flash not only poses problems, but can also indicate perfectly healthy eyes.
The above image shows different eye colors in photos with their meanings. In the upper right, the pictured eye could indicate a rare childhood cancer – retinoblastoma – and in the bottom left, the pictured white eye could be a sign of a disease where blood vessels leak into the eye.
Doctors from the American Academy of Ophthalmology recently raised concerns that too few people are taking advantage of this useful healthy check – due to the advent of image editing features on smartphone cameras that smooth out imperfections.
The experts said that a flash reflection that illuminates the eyes in a bright red color is a useful indicator that the retina is ‘blood-rich’ – a ‘good sign’ that ‘both eyes are unobstructed and healthy’.
“A red reflex occurs when a camera flash illuminates the blood-rich retina,” the doctors said.
“If the eyes look directly into the camera lens and the color of the reflex in both eyes is red, that is usually a good sign that the retinas of both eyes are unobstructed and healthy.”
Crucially, the flash reflection can also show signs of unhealthy eyes.
For example, cases where one eye is less red than the other – medically called asymmetric red reflex – can be a warning sign of strabismus, a condition in which both eyes do not face in the same direction.
This happens because of problems with the muscles that control the movement of the eyeball, which affects about four percent of American adults.
Other warning signs include vision problems, bumping into objects, and eyes that don’t move together.
Doctors say it’s best to detect the condition early, when it’s easiest to treat.
Treatments include wearing glasses or surgery to strengthen one of the eye muscles.
In cases where one or both eyes are white, ophthalmologists said it could be a sign of a rare form of cancer called retinoblastoma, or eye cancer.
The discoloration is caused by light reflected from white-colored cancer cells at the back of the eye.
Retinoblastoma is a rare childhood cancer that occurs when cells begin to divide uncontrollably in the retina. About 300 children suffer from this every year. Other warning signs include poor vision and eye pain.
Doctors said a white eye could also be an indication of retinal detachment or an infection.
When the retina becomes displaced, it reflects light differently, while the structure of the cells can change if it is infected.
About one in eight children gets an eye infection every year, doctors say.
In some cases, the eyes may also appear yellow in photos, doctors said.
This could be a warning sign of Coats’ disease – when the blood vessels in the eye become twisted and leaky.
Scientists suggest the disease may be caused by genetic mutations that lead to a build-up of cholesterol deposits in the eye – which reflect yellow against a camera flash.
There are about 100 cases a year, usually in boys, and the condition can be treated with surgery or cryotherapy, which uses blasts of cold air to remove abnormal tissue.