The impact of eyelid edema on the results of trans-palpebral rheoophtalmography

Measuring the parameters of eye hemodynamics is an important issue in ophthalmic diagnosis. Eye hemodynamics needs to be examined in early diagnosing of a variety of widespread diseases, including myopia, glaucoma, and diabetic retinopathy. It is also important to be able to assess the changes of bloodflow parameters in order to determine the effectiveness of surgical or medicinal treatment of these diseases.

Eye hemodynamics is measured by a variety of methods. In the present study, we chose the method of rheoophthalmography. The patents were divided into two groups depending on whether they had or had no eyelid edema. The signals of the rheooph-thalmogram were used to measure the rheographic index and basic impedance before and after treatment. We offered a new geometric model of the eye to assess how eyelid edema influences the bloodflow parameters and the accuracy of diagnosis. In the model, the eyelid edema is presented by an enlarged eyelid layer with a pitch of 2.3 mm and an altered geometry of sift tissues adjacent to the eyelid. Two versions of edema manifestation involving an increase of the axial size of the eyelid layer proportionally to its thickness. In the first case the thickness of the eyelid was doubled while in the second case it was tripled. In the study, mathematical modeling was done for three cases: normal eye geometry, twofold and threefold increase of eyelid thickness.

We found that the presence or absence of an eyelid edema is an important fact, which has to be mentioned in the case history and used in the diagnostic process as it determines whether the interpretation of transpalpebral rheoophthalmography is correct. When using this technique, it is only possible to place the electrodes correctly if the edematous eyelid is less than 4.6 mm thick.

The paper was supported by a grant from RFBR (No.15-08-99682).