The all-seeing eye can show your heart health - and many other issues

Dr Miriam

Diagnosis: Eyes can show your health

I've always thought that our eyes act as windows on the body. If you look at the back of the eye, you can get a glimpse of the arterial health of the rest of the person.
On the retina, you can examine the arteries supplying the back of the eye and, if you see signs of disease there, you can bet your life there's disease throughout the whole arterial tree, including the heart.

If the back of the eye was the only clue available, a doctor could still diagnose high blood pressure, diabetes, furring up of the arteries and coronary artery disease.
And the research of two ophthalmologists, working at the University of Kansas, US, implicates the eyes in many more conditions.

Their studies supply an answer to why memory loss, depression, slowing reaction times and insomnia get worse as we age.

It turns out the ageing eye lets less and less sunlight through the narrowing pupil and the opaque lens (think cataracts) to reach the cells in the retina.

These cells tell the brain what time of the day it is: it's morning (light) and time to wake up, it's night (dark), time to go to sleep. In other words, the ageing eye prevents the regulation of our body clock.

The effects are huge. People whose body clocks are out of sync, like shiftworkers, are at greater risk of several diseases of advancing age such as heart disease and cancer.
This failure to regulate our body clock shows up as the insomnia of old age and it has a knock-on effect.

People with disturbed sleep have a tendency to become obese with all its attendant hazards. Just as important, insomnia gives the body no downtime for rest and repair.
The eyes communicate with the brain in a very intimate way.
They have a direct line to the time-keeping centre in the brain, the suprachiasmatic nucleus.
It releases melatonin in the evening (so you go to sleep) and cortisol in the morning (to wake up).

Without sufficient light it goes awry and its sensitivity to light quickly fades - the amount of light which suppresses melatonin in a 30-year-old woman has no effect on 50-year-olds.

And researchers in Sweden have found insomnia and daytime sleepiness improves after cataract surgery.

Their prescription is to expose your eyes to more sun as you age and make sure any lighting you're exposed to is bright.

I would also get outdoors as much as you can.

Artificial light is 1,000-10,000 times dimmer than outdoor light so put skylights in and bright fluorescent lights in rooms, which have little daylight.

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