Large movements in the visual field trigger stereotypic eye movements in vertebrates. This optokinetic response
(OKR) is robust in zebrafish (Danio rerio) larvae older than 4 days post-fertilization (dpf), and is hence ideally
suited for use in the evaluation of visual performance after genetic manipulations. This protocol describes a simple
method by which a computer-generated visual stimulus is projected onto a screen and watched by immobilized
larvae. The resulting eye movements are recorded and evaluated automatically, using a digital video camera and
appropriate computer software. Depending on the sophistication of the software used, the evaluation can be
performed in real time during the recording session, or by analyzing the recorded movie files off-line.