 The first reliable instrument to measure intraocular pressure was invented by Norwegian ophthalmologist Hjalmar August Schiøtz in 1905.About half a century later, Hans Goldmann in Berne, Switzerland, developed his applanation tonometer which still today - despite numerous new innovations in diagnostics - is considered the gold standard of determining this crucial pathogenic factor.In the late 20th century, further pathomechanisms beyond elevated IOP were discovered and became the subject of research like insufficient blood supply – often associated with low or irregular blood pressure – to the retina and optic nerve head.