New device for artificial increasing intraocular pressure

For certain special investigations, particularly in glaucoma diagnostics, intraocular pressure has to be increased. Mostly, a suction cup apparatus is used for that purpose. These devices, however, have some disadvantages. They are at least uncomfortable, sometimes risky for the patient and induce a strong astigmatism which can influence the results of the corresponding investigation.

A very simple mechanical device has been constructed and tested, by means of which the intraocular pressure can be increased for diagnostic purposes. A ring on a lever, which is moved towards the eye by small weights, compresses the eye through the lids without the need of even local anesthetics. The device can be easily mounted to any head fixation which is normally used in combination with ophthalmological equipment. e.g. slit lamp, visual field analyzer or fundus camera. Tests have been performed in four different groups: one group of 19 healthy volunteers, one of 21 patients with Graves' disease, one of 21 patients with high myopia and one of 20 patients with open-angle glaucoma.

Pressure elevations could be achieved in all patients with very good reproducibility with respect to the applied forces. However, in patients with exophthalmos (Graves' disease), the elevation effect was somewhat higher than in normal eyes. The induced astigmatism was only about 0.5 dpt for pressure elevations of about 20 mmHg.

The tests performed showed that the new device is easy to handle and comfortable for the patients. If very high accuracy is needed concerning the pressure values achieved, an individual calibration should be performed.