An ophthalmologist in Tehran has documented more than 400 eye injuries from gunshots in a single hospital, as overwhelmed medical staff struggle to cope with the toll of an increasingly violent crackdown on nationwide protests by Iranian authorities.

Three doctors, in messages forwarded to the Guardian on Monday, described overwhelmed hospitals and emergency wings overflowing with protesters who had been shot. Medical staff said the gunshot wounds were mostly concentrated on protesters’ eyes and heads – a tactic that rights groups said authorities used against demonstrators in the country’s 2022 Woman, Life, Freedom protests.

“[Security forces] are deliberately shooting at the head and the eyes. They want to damage the head and the eyes so they can no longer see, the same thing they did in [2022],” said a doctor in Tehran. The doctor added that many of the patients had to have their eyes removed and were blinded.

Iran’s demonstrations, which started on 28 December over a sudden dip in the value of the country’s currency, have since turned into the country’s biggest anti-government protest movement since 2009. Tens of thousands of protesters have taken to the streets across the country each night, chanting anti-government slogans such as “death to the dictator”, a reference to the Iranian supreme leader, Ayatollah Ali Khamenei.