In industrialized countries, the second most common cause of blindness, after diabetes, is glaucoma. For example, in Germany every year around 28000 people are additionally suffering from blindness due to glaucoma. For the major part of these patients, damage could be prevented by an early diagnosis and treatment.For the diagnosis and also during treatment of glaucoma, tonometry, which is the evaluation of the intraocular pressure, is an important method.
However, for the classification of glaucoma, the intraocular pressure is insufficient as the only parameter, because around 30% of glaucoma patients show damage of the eye while still having normal intraocular pressure values (normal pressure glaucoma). On the other hand, there exist many patients having an increased intraocular pressure without suffering the disease. Hence, for the successful diagnose of glaucoma a combination of several parameters is necessary.It is presumed that blindness due to glaucoma can be traced back to an insufficient blood circulation inside the eye. This may affect the nerves of the photoreceptors or the photoreceptors itself, both located on the retina. Thus, the circulation of the eye is thought to be an important parameter for the early diagnosis of glaucoma.
It is assumed that the blindness caused by glaukoma is due to circulatory disorder of the visual receptors and the visual nerve. The circulatory properties of the eye, especially of the retina, is believed to be a signifficant parameter for galucoma screening. Tonometry combined with circulation measurements of the eye may bring advances for the successful diagnose of glaucoma. In the method here applied, the circulation induced pulsatile movements of the cornea is measured by the use of a laser interferometric setup. From the analysis of these movements, statements about the blood supply of the retina as well as about the value of the intraocular pressure can be made.
Optical Measurement System
An already implemented stationary measurement system is consists mainly of an optical sensor head and a control and processing unit. The system is able to measure the pulsatile eye movements with a high precision. Of great importance when designing a laser measurement system is to respect the laser safety regulations. As the system is thought to be used for long-term monitoring, the light radiation to the eye has to be limited to a minimum. Hence, the detection of the reflected light building the interference signal is a crucial issue.
Besides the high precision stationary measurement system, the realization of camera based system is in progress. This simplifies the miniaturization of the concept to result in a hand-held device. In this way, it will be possible to continuously determine the intraocular pressure as well as the blood supply of the eye, which may be done after operation or for diagnoses purposes.
Such measurement device will enable completely new ways of diagnosis and therapy. This includes glaucoma and also other diseases related to circulation of the head / brain.
Personal Health Monitor (PHMon)