The eyes reveal more than what is in the heart - in fact, they reveal exactly when you were born, according to a new study.

The study, by researchers at the University of Copenhagen and Aarhus, used radiocarbon dating and special proteins in the lens of the eye to establish - with relatively high precision - when a person was born.

This provides a useful tool for forensic scientists who can use it to establish the date of birth of an unidentified body and could also have further consequences for health science research.

Findings of the study have been published in the online, open-access journal PLoS ONE.

Eye lens is made up of tightly packed transparent proteins called crystallins that, like crystals, allow light to pass through so that we can see.

These crystalline proteins are built till a human is 1-2 years of age - but after that they remain essentially unchanged.

Researchers have now used this fact to help establish the age of people by carbon dating the crystallins.

Apart from ascertaining the age of people, the findings of the study have other potential uses.

Said Niels Lynnerup, who headed the study: 'We think that the carbon dating of proteins can also be used to study when certain kinds of tissue are generated and regenerated. This could, for example, be applied to cancer tissue and cancer cells.'