More doctors should be taught simple test that can prevent blindness, according to a Birmingham specialist.
A survey, carried out for four months in 2011, found almost half the patients referred to Birmingham's City and Queen Elizabeth Hospitals with head pain had not been examined by using an ophthalmoscope.
This shines a light into the back of the eye to detect signs of pressure on the outside of the brain.
Eighty per cent of the patients surveyed at Queen Elizabeth Hospital said they had not had the eye test. When doctors were written to about these findings and a second check done, 60% of patients still had not undergone the basic examination.
Dr David Nicholl, who works at both hospitals, became concerned after he was asked to discharge patient Katherine Pryor from City Hospital on Christmas Eve in 2008.
Ms Pryor had initially been sent home from accident and emergency after being told that she was having a panic attack.
Ten days later, eight of which had been spent in hospital, she was unable to see when Dr Nicholl was called to sign her discharge papers.
He immediately referred her for surgery which restored her sight.
The 28-year-old now lives a normal life, but she nearly went blind.
She said: "He sent me for an eyesight saving operation if not a life saving operation. I can't imagine what it would be like to be blind."
Following Dr Nicholl's concerns, the QE spent £1,000 on new ophthalmoscopes, but they all went missing within two weeks.
Fixed ophthalmoscopes are now in place at City Hospital and Dr Nicholl is encouraging junior doctors to buy their own for around £70.
This compares to £275,000 paid out in compensation in 2004 by Hillingdon Hospital when a young girl was misdiagnosed and went blind.
The study, which was published in the journal of the Royal College of Physicians of Edinburgh, states several medical schools do not teach or test how to examine eyes. Dr Nicholl and his fellow authors are attempting to ensure doctors are given a final year exam which includes the test.
Dr Nicholl said: "I would actually argue that if you are talking only about headache, the only bit of the patient examination that you must do involves an ophthalmoscope."
University Hospitals Birmingham NHS Foundation Trust which runs the two hospitals said it welcomed the study's findings.
"The research highlights that a relatively simple tool can be used very effectively to improve patient assessment and, ultimately, outcomes, a spokesman said."