REFRACTION CHANGES DURING ELEVATION OF INTRAOCULAR-PRESSURE BY SUCTION CUP, THEIR REFLECTION IN THE PATTERN VISUAL-EVOKED CORTICAL POTENTIAL AND THEIR COMPENSATION

Visual evoked cortical potential studies using pattern stimuli with th e intraocular pressure raised artificially by the suction cup method h ave been reported. Possible changes in the refraction of the eye due t o the method employed and their influence on the pattern visual evoked cortical potential have not been considered. Changes in the refractio n of the eye during artificial intraocular pressure elevation and the influence of such changes on pattern visual evoked cortical potentials were studied. The refraction changes were found to depend on the shap e of the suction cup. They could be compensated for by employing prope rly shaped suction cups and contact lenses. The behavior of amplitude and latency of the pattern visual evoked cortical potential at artific ially elevated intraocular pressure with compensation for refraction c hanges has been studied and found to depend in a characteristic manner on ocular perfusion pressure.