Although the eye is the only organ in the body in which blood vessels are readily visible, a technique for the accurate and reproducible measurement of ocular blood flow and its component parts has proved elusive.1 The increasing likelihood of a multifactorial pathogenesis for glaucoma and possible importance of optic nerve head perfusion in the pathogenesis of glaucoma has added impetus to the search for a clinical method of measuring ocular blood flow. The pulsatile variation in ocular pressure results from flow of blood into the eye during cardiac systole. First recorded in 1850 by Wegner,2 various methods have been tried to record the pulsatile variation in intraocular pressure. Langham and co-workers3 adapted the pneumotonometer to measure intraocular pressure every 30 ms thus obtaining an accurate record of the pulsatile change in pressure. They hypothesised that the pressure pulse could be converted into a …