It has long been known that elevated intraocular pressure is an important risk factor for the development of glaucoma. Likewise, unstable blood flow to the back of the eye is a crucial cause. About 40% of glaucoma patients have normal intraocular pressure, but the eye is sensitive to blood pressure fluctuations. Therefore, close observation of the cardiovascular system supports diagnosis and therapy. For the investigation of vascular dysregulation, the CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH together with aviant GmbH from Jena developed a multisensory solution that records ECG and photoplethysmographic parameters synchronously in time.
An increased intraocular pressure is often the cause for the development of glaucoma. However, disturbed blood flow to the back of the eye also plays an important role. If nerve or visual cells are not sufficiently supplied with blood, they can be damaged. This leads to degradation of the optic nerve and eventually to visual field loss. In patients with normal intraocular pressure, this is often due to a so-called vascular dysregulation. In this case, the vascular system is no longer able to adapt to the requirements of oxygen and nutrient supply to the eye to the necessary extent.
According to current knowledge, in normal pressure glaucoma patients not only the eye is diseased, but possibly the cardiovascular system of the body in general. Studies show that these patients suffer to an increased degree from circulatory disorders, e.g. in the hands or from heart disease.
The time-synchronous measurement of ECG and PPG should enable the screening of vascular dysregulation with a good sensitivity and, above all, a very high specificity.
By using modern low-power electronics and resource-saving technologies of microsystems engineering, a solution was created that enables mobile monitoring of vital parameters, e.g. in ambulatory use.
The heart of the device, the PPG sensor for detecting the pulse wave, is characterized by high signal quality and excellent wearing comfort. Hidden in an earmold, the sensor can be worn on the ear and can thus be used by the patient in everyday life without any restrictions. This was made possible by the integration of a special optical emitter-receiver module manufactured using chip-in-chip technology. Established standard components were used for the ECG electrodes. The achieved resolution and sampling rate of ECG as well as plethysmogram are 24 bit, 200/100 Hz each.
A further “delicacy” of the Thuringian inventors is a handy system electronics in the dimensions of 100 mm x 40 mm x 20 mm, which is operated with two AA batteries. In addition to the sensor control, it contains a data logger with low-noise and low-drift pre-amplification and signal processing. Data can be stored either on a conventional SD card or on the physician’s PC via a USB interface.