Self-operable tonometer for measuring intraocular pressure of a patient's eye

摘要

A tonometer for measuring intraocular pressure (IOP) allows a user to self-operably apply a removable, lightweight, ocular probe to gently flatten an area of the corneal surface. A transducer having a flexible springboard connected to the probe and serving as a plate of a variable capacitor is used to sense forces produced when the probe contacts the eye elastically deforming the springboard. The applanation area is detected with a video camera connected to a central processing unit (CPU) programmed to perform image analysis. The CPU uses multiple force and multiple area values determined in rapid succession so that force and applanation area data are closely related in time. Linear regression analysis is used on data pairs to determine an average value for IOP in only about 1-2 seconds. The probe has a clear window with markings for delimiting a calibration area. The slight passive movements of the probe in this process are frictionless and cause no error in force determination. The IOP determination is independent of gravity and thus may be carried out in any orientation as well as under the condition of weightlessness.