Tonometria e proprietà oculari: analisi delle proprietà termofisiche per un tonometro termofisico privo di contatto = Tonometry and ocular properties: analysis of thermophysical properties for a non-contact thermophysical tonometer

Intraocular pressure (IOP) is the force exerted by the aqueous humor on the internal surface area of the anterior eye. IOP value is regulated by production and drainage of aqueous humor continuously secreted from the ciliary epithelium of ciliary processes. Disruption of aqueous outflow results in elevation of IOP, the main risk factor for developing glaucoma, which is the second commonest cause of blindness globally, due to the retinal ganglion cell death. Consequently, IOP measurement and reduction are important in detection and treatment of glaucoma. Goldmann applanation tonometry (GAT) is the standard measurement method, but it is affected by corneal properties, such as central corneal thickness (CCT) and corneal curvature (CC), also changed by refractive surgery. In this study, the factors that significantly influence the IOP measurements in standard condition and for the most widely used tonometers were identified. In general, it was found that IOP is a dynamic variable with diurnal fluctuation that occurs daily, short-term fluctuation that occurs over days to weeks, and long-term fluctuation over months to years. However, the IOP readings are mostly affected by corneal thickness and biomechanical properties such as hysteresis and corneal rigidity. The purpose of this study was to use a different approach based on thermophysical analysis of corneal properties for studying IOP. Corneal temperature is involved in the aqueous humor dynamics, so the idea was to exploit the ocular infrared thermography as a possible non-contact and non-intrusive IOP measurement method. To investigate the relation between central corneal temperature (𝑇𝑐) and intraocular pressure, tonometric and thermal measurements were performed at the ophthalmologist clinic Vercesi in Tortona (Alessandria). Inverse proportionality between 𝑇𝑐 and IOP was observed in a group of 9 patients. However, further investigations are needed to obtain clinically useful information.