High street opticians could one day be used to diagnose depression, a study has suggested.

Scientists have found that specialist images of the back of the eye, often included as part of standard eye tests, can hold clues as to who might be at risk of depression years later.

Their research, based on a study of 40,000 British adults, found those with wider veins leading to the retina – a layer of light-sensitive tissue at the back of the eye – were up to 50 per cent more likely to develop depression over the next decade. 

One theory is that depression can drive chronic inflammation throughout the body, which may cause the veins of the retina to widen as a result.

Ophthalmologists from the International Eye Centre at Shantou University in China analysed eye imaging data from healthy men and women, who were then followed for an average of 11.3 years. 

During that time, 1,402 of them were diagnosed with depression – and scientists found that having wider retinal veins was associated with a 25 per cent increased risk of the condition.

They added that, in the absence of an objective test for depression, retina images could be a ‘promising, accessible candidate’ to help diagnose it. 

Writing in the Journal of Affective Disorders, the researchers said: ‘Our study... provides strong evidence that vein widening precedes clinical depression onset.’

However, they added that more research was needed before images of the retina could be used to diagnose the condition.