Manometiric studies of the pressure-volume relationship in living and enucleated eyes of individual human subjects

Abstract

(1) The relationship between pressure and volume changes in six human eyes has been studied both before and immediately after enucleation. The observations were made by recording manometrically the intra-ocular pressure either to a sudden injection of a predetermined volume of saline or to a continuous infusion of saline. (2) A continuous infusion of 197 μI. min.-1 of saline was found to give a different pressure response in the living and dead eye. In the dead eye the slope of the curve increased continuously, whereas in the living eye the slope increased to approximately 60 mm. Hg and then reversed until the intraocular pressure exceeded the mean blood pressure, at which level the slope began to increase again. Reasons are given for associating these changes with loss of blood from the eye. (3) Calculations of the coefficient of ocular rigidity for 5 mm. Hg pressure steps over the pressure range of 20 to 65 mm. Hg were made from the results of the two techniques and the values were essentially the same. Further-more, they confirmed the conclusions of recent investigators that the coefficient decreases in value with an increased pressure in the eye. (4) In individual eyes the coefficient of ocular rigidity was significantly greater in the enucleated than in the living eye at corresponding pressures in three out of the six eyes studied. In the remaining three eyes the difference was either small or insignificant. (5) The significance of these results is discussed in relation to recent investigations and to tonographic analysis.