It's in the eyes

"You could go to the ophthalmologist and he'll say, 'Go to your gynecologist! It looks like you might have breast cancer,'" says Professor Walter Konen from the clinic at the University of Cologne.

"I do not see every case of breast cancer, but with a woman who is going to die soon, I can see the metastasis in the fundus, and then I know that she won't live more than six months," he explains.

But things are not always that extreme. Ophthalmologists can recognize many diseases - often before diagnosis by another specialist. Diabetes, high-blood pressure and multiple sclerosis can all be made out in the eye. Diseases associated with other areas of medical specialization - like rheumatism or liver problems - often come to light in routine eye examinations.

"Yellow sclera, which are the whites of the eye, can indicate that there is an illness. And that has to be investigated. Often, a liver disease plays a role," says Kone, adding that it could be a case of acute or chronic hepatitis, for example.

More than meets the eye

If a patient heads to the ophthalmologist for reading glasses, but finds that he has diabetes, then he is likely to be shocked because most people do not know that such diseases can be diagnosed by an eye examination.

Diabetes leaves traces that are clearly recognizable to the ophthalmologist.

"In diabetes we see fine outgrowths of the vessels, called microaneurysms and dot hemorrhages in the retina," says Professor Berthold Seitz, president of the German Ophthalmological Society (DOG).

During an examination, the pupil is dilated, and then the doctor looks into the eye with an ophthalmoscope. There are methods through which the eye can be examined by magnifying it 60 times, says Seitz. That way, the doctor can recognize the typical signs for several diseases, particularly diabetes, which affects a large segment of the population. The small blood vessels in the eye allow for inferences about the health of the total vascular system.

With diabetic retinopathy, there is a high amount of sugar in the blood, which destroys the retina and the fine blood vessels, and it can lead to blindness. Around 30,000 Germans are affected, and every year, 2,000 of them lose their sight due to diabetes. Working intensively with other specialized areas of medicine is part of Seitz's daily routine.

"Every day, 60 to 70 patients come to our clinic. Every one to two days, there is someone where we recognize something that could have something to do with a general disease," says Seitz.

Multiple sclerosis, rheumatism and Wilson's disease

And it's not just diabetes and high-blood pressure - ophthalmologists can also diagnose autoimmune diseases like multiple sclerosis (MS). In MS, the immune system destroys the myelin layer - the coating of the nerve fibers. In most cases, inflammation forms throughout the nervous system. That can lead to slight discomfort, but it can also cause immobility or severe disability in some cases. Often a particular nerve is affected that controls eye movement, leading patients to experience double vision or become visually impaired. For ophthalmologists, that could be a possible indication of MS. The disease isn't curable, but the earlier it is diagnosed, the better the chances for therapy.

Diagnosing rheumatism isn't rare for an ophthalmologist. Here, the indicator is typically inflammation of the iris, says Seitz.

"That's like being in a hut on a mountain, and there is fog in the morning. And then rays of sunlight come through," he explains.

The somewhat milky cloud that can be seen is an inflammation of the iris in the chamber of the eye.

Wilson's disease can also be recognized by examining the eyes. It is a rare disease that goes hand in hand with a gradual destruction of liver, says Seitz.

"There is a Kayser-Fleischer ring. That's a brown ring that can be recognized in the depth of the cornea, and which is formed by the deposit of copper," he adds.

Interdisciplinary work

The subject of how eyes provide a window into other diseases is part of the training for ophthalmologists, says Seitz.

"That's actually my favorite subject, because you can go from A to Z, and show that ophthalmology isn't just about cataracts and glaucoma or even worse, about glasses," he says.

For some patients, it's very clear what role their ophthalmologists played in diagnosing their illness.

"There are always patients who sing our praises after having helped to identify an underlying disease that would have otherwise gotten worse," Seitz says.