What your eyes say about your health
You can learn a lot about a person from gazing into their eyes. Eyes are not only the mirrors of the soul but provide a unique window into a person's health.
It's not only disorders of the eye that can be detected but other diseases and conditions which you may not even be aware of like diabetes, cardiovascular problems and sometimes, but rarely, brain tumours.
What eye tests may reveal
"As part of a standard eye examination the back of the eye is examined and as the blood vessels on the retina can be seen it gives you a sense of the health of the vascular system and [you can] observe changes occurring in systemic diseases that affect the vascular system, like high blood pressure and diabetes," says John Lawrenson, professor of clinical visual science at City University London.
He says the examination can be used to monitor conditions or it can be diagnostic.
Health problems relating to the brain like tumours or other space-occupying lesions can sometimes be detected too.
"Conditions that cause raised intracranial pressure can be seen in an eye examination. For example, brain tumours can be detected when there's raised pressure and swelling observed where the optic nerve leaves the eye," says Professor Lawrenson.
He adds: "The pituitary gland at the base of the brain is anatomically close to the visual pathway. If the pituitary gland is enlarged by a tumour it can compress the visual pathway and lead to a characteristic loss of peripheral vision."
There are a number of other systemic diseases and conditions that may show themselves in the eyes, including an overactive thyroid, multiple sclerosis and infectious diseases such as HIV/AIDS.
Common eye conditions
We asked Professor Lawrenson what common eye conditions that you can see for yourself may signify:
Blood shot eyes - This usually occurs when small delicate blood vessels dilate in response to irritation or infection. These vessels can also leak and cause a haemorrhage.
Grey rings around the cornea- It can happen with age but in a younger person it can indicate a lipid disorder. If you have a family history of lipid dysfunction it could mean an increased risk of heart attack and stroke.
Yellow eyes - Yellowy lesions on the eye and skin near the eye may signify raised cholesterol. If the whites of the eyes are tinged with yellow it could indicate jaundice due to compromised liver function.
Floaters - Most people have them to a greater or lesser extent. The jelly inside your eye is mostly water but it contains fine fibres which can aggregate together and cast a shadow on the retina. If you are getting a sudden increase in floaters it could signify retinal detachment and an eye care professional should be consulted as a matter of urgency.