Physical and physiological basis

The pulsation phenomena occurring when extravasal pressure is elevated form the basis of ophthalmodynamometry, as is the case when blood pressure is measured using the Riva Rocci principle. When diastolic blood pressure is exceeded the intermittent vascular collapse in the eye can be observed directly, whereas, when blood pressure is measured in the arm, only indirect auscultation of collapse is possible in the form of Korotkoff’s sounds. Because the eye is an almost spherical body every change in shape leads to an elevation of intra-ocular pressure. This physical law forms the basis for all procedures or devices, by which environmental pressure in the eyeball or intraocular pressure can be increased. Pulse phenomena are either observed by ophthalmoscopy or registered electronically. With the contact lens dynamometer the contact lens is used to observe the pulse phenomenon and this in itself increases intraocular pressure.