Motivation

In the industrialized countries the second prevalent reason for blindness after diabetes is glaucoma. In Germany itself 28000 people go blind because of glaucoma every year. For a major part of these patients damage could be prevented by an early diagnosis and treatment. Up to now the most relevant parameter for diagnosis and treatment of glaucoma is the measurement of the intraocular pressure (IOP). However, this parameter by itself is insufficient for the classification of the disease. Around 30% of the patients show a damaged retina while still having normal intra ocular pressure values (normal pressure glaucoma, NPG). On the other hand, there do exist many patient having a increased IOP without suffering the disease.

Method

A second important parameter is presumed to be the blood flow inside the retina. Thus, the main goal sub-project IOP is the design and development of a miniaturized hand-held tonometer, providing the intraocular pressure as well as giving an indication for the blood flow inside of the eye. Therefore, a modified flow sensor is measuring the peripheral blood circulation of the head. Together with the via a laser interferometer measured pulsating movement of the corneal surface, information about the blood supplied to the retina is gathered. Also, a measure for the amount of intraocular pressure can be given.

Realization

The system measuring the pulsating movement of the retina is consisting of a mechanical adjustment device, an optical sensor head, and an electronic control and processing unit. In the ongoing design and integration process, the currently stationary sub-system is going to be realized as an hand-held one.

Measurements

With the above described system, several in-vivo measurements were done. Together with the pulsating amplitude of the corneal displacement and the blood circulation signal on the ear was measured. From the analysis of this two signals a statement about the blood circulation inside the retina as well as about the IOP can be given.