Lockdown has seen a “disturbing” rise in the number of blind people experiencing distressing hallucinations, the RNIB charity says. The condition, known as Charles Bonnet syndrome (CBS), causes patients to have vivid hallucinations. False images are triggered when the brain tries to fill in the gaps caused by sight loss. The RNIB said calls to its helpline had increased by almost 50% and patients had reported more sinister visions.CBS is thought to affect up to 30% of those with sight loss, although it can sometimes be confused with mental health concerns.