An international team of researchers has found a clue to one of the leading causes of blindness, which they hope could eventually lead to a cure.
Age-related macular degeneration affects 500,000 people in the UK and is incurable.
The study in the journal Nature found an enzyme known as DICER1 that stops functioning, resulting in the illness.
UK experts said it had the potential to be an important breakthrough.
The macula is a part of the eye which sits in the centre of the retina and is responsible for the fine detail at the centre of the field of vision.
As the disease progresses that central vision declines, making reading, driving and recognising people difficult.
It affects one in 50 people over 50 and one in five people over 85.
The exact cause is unknown, but risk factors include smoking, high blood pressure and having relatives with the condition.