Ocular rigidity and hydrodynamics of the human eye

Abstract

Purpose The intraocular pressure (IOP) is the primary mechanical load to several ocular structures. It fluctuates over time as a result of a dynamic equilibrium between the systems of aqueous and blood flow. The purpose of this study is to characterize the eye’s pressure volume relationship and quantify hydro and haemodynamic parameters in the living human eye. Methods An invasive manometric dynamic measurement procedure was developed and used in a series of healthy and pathological eyes measured intraoperatively before cataract surgery. Different measurement protocols involving injection of predetermined doses of saline and monitoring the IOP in a time‐resolved manner, allow the measurement of ocular rigidity, outflow facility and pulsatile ocular blood flow. In addition, a new non‐invasive ultrasound based technique enabled us to visualize and define the elastic properties of the ocular globe and periocular structures. Results Measurements in humans indicate that the above techniques are safe and effective. A non‐linear pressure‐volume relationship is established. The ocular pulse amplitude (and therefore pulsatile ocular blood flow) is shown to correlate with IOP. Conclusion A model that incorporates ocular rigidity is proposed in order to describe and quantify the relationship between hydrodynamic and hemodynamic parameters of the human eye. These measurements along with the use of new non invasive techniques may improve our understanding of the relationship between these parameters and their significance in health and disease.

A study comparing ocular pressure pulse and ocular fundus pulse in dependence of axial eye length and ocular volume

“…In recent years there has been increased interest in the interpretation of the ocular pulse amplitude, because it is measured easily using dynamic contour tonometry (Punjabi et al 2006a(Punjabi et al , 2006b). Moreover, only recently a new technique for measuring POBF was presented Pallikaris et al 2008).…”