An Illinois mother recently discovered her son had cancer from how his eyes looked in an iPhone photo.
[WEB EXTRA: More on the National Eye Institute ]
There are hundreds of diseases and ailments that doctors can tell about your health by examining your eyes.
"A large part of a good eye examination is about medical health," Dr. Harry Pappas said.
Pappas is an Ophthalmologist at the Florida Eye Clinic.
He says most people wait until they have vision problems to get an eye exam, which is why Jennifer Evans, an Orlando mother is getting her eyes checked.
"As I've gotten older, I have to hold the book farther away, and stuff like that, its more of a hassle," Evans said.
Pappas says eye exams can tell doctors much more about your health than just your vision.
"There are many, many medical conditions which show up in the eyes," he said. "For instance, brain tumors can present with eye problems. Multiple Sclerosis, which is a debilitating problem, can show up as decreasing vision. HIV/AIDS can show up as decreasing vision."
During a routine full eye examination, the doctor dilates the pupil of the eye so that he or she can see inside.
Inside the eye, you can see the circulation of the body, and the Optic Nerve which is an extension of the brain.
Swelling can be a red flag.
"There are a number of things that can cause swelling of the Optic Nerve, but one of them would be a brain tumor so that patient would get referred out for other examinations, an MRI, a visit with a neurologist," Pappas said.
During eye exams, doctors are often looking for what they call the big four:
1) Cataracts, which are the most common age related change to your eyes according to Pappas
2) Glaucoma, which is one of the major causes of blindness worldwide.
3) Age related Macular Degeneration, which is the leading cause of decreased vision in Americans over 65.
4) And Diabetic Retinopothy, which is complications related to diabetes.
Adults with no signs or risk factors should have a comprehensive eye exam in their 20s and definitely by 40, according to the American Academy of Ophthalmology.
By age 65, 1 in 3 Americans have some visual impairments, according to Pappas.
Pappas says the sooner many conditions are caught, the better the end result.