Charles Bonnet syndrome (CBS), a complication of sight loss, is characterised by the vivid, silent hallucinations that occur when the brain overcompensates for the lack of information it receives from the retina by creating its own pictures.

According to the Macular Society (2020), almost 1.5 million people in the UK are affected by macular disease, half of whom experience CBS hallucinations.

These visions are not a sign of mental illness but a natural, if sometimes debilitating, experience. They can manifest in several ways, from flashes of light, colour or shapes to geometrical grids and lattice patterns. For some, the images are more terrifying and take the form of distorted faces, crawling spiders or slithering snakes.