A visual apperceptual abnormality, persistent peripheral oscillopsia, was first noted by a London, UK, ophthalmologist in 1946 in veterans from the Second World War suffering from what was then called Traumatic Neurosis, now called Post Traumatic Stress Disorder.We studied this visual abnormality.We devised a quick, simple, reliable and sensitive clinical test for it.When (a) persistent peripheral oscillopsia is found present it is virtually always accompanied by (b), one or more abnormal recurrent experiential (re-experiencing) iconic-image visual and other sensorial memory flashbacks of the most frightening moment of one or more acute-fear experiences in the past.