The visual field of 27 eyes with chronic open angle glaucoma was examined with the "Octopus 1-2-3" automatic perimeter. The visual fields with and without miotics were compared using the "mean defect" (MD) as parameter. The MD decreases significatively (p = 0.003) after interruption of the miotic treatment. As presumed, the IOP and the pupillary diameter increased significantly (p less than 0.001). The CLV insignificatively decreased. The short term modifications of the pupillary diameter seem to be a more important factor than this of IOP.