Fundus Pulsation Measurement By Laser Interferometry - A Noninvasive Technique For The Assessment Of Hemodynamic Drug Effects

The pulse-synchronous pulsations of the eye fundus are measured by laser interferometry. The eye is illuminated by the beam of a single mode laser diode. The light is reflected at the front side of the cornea and the retina. The two remitted waves product interference fringes, from which the distance changes between cornea and retina can be determined. The interferometer is coupled to a fundus camera, so that fundus pulsations can be measured at preselected points on the retina with high transversal resolution. This technique was used to study the influence of phenylephrine (a peripherally vasoconstricting drug), isoproterenol (a predominantly positive inotropic drug), sodium nitroprusside (a peripherally vasocilating drug) on fundus pulsations in healthy volunteers. The effect of isoproterenol to increase pulse pressure amplitude was detectable even at low doses. Neither sodium nitroprusside nor phenylephrine had a significant influence on ocular fundus pulsations. These results show that measurement of fundus pulsations in the macula estimates the pressure pulse amplitude in choroidal vessels. Measurements of fundus pulsations at preselected points of the retina, show that fundus pulsations in the macular region are larger than in peripheral parts of the retina but smaller than in the optic disc region under baseline conditions.