Samenvatting
One factor to be controlled in dark adaptation testing is that ( of fixation 80 that the region of the retina under investigatior is known and constant. Thit is rather easily controlled during the bleachin phase, but in the test phase te subject is tempted t deviate from the conventional red fixation light ..search the area in which the test object is anticipated. This may not be a serious detraction for a trained subject, byt is is very disconcerting to both the naive subject and the conscientious test operator.