Visual fields and eye movements in a harbor seal (Phoca vitulina)

The boundaries of the visual fields of a harbor seal were measured using static perimetry. In the seal lying on a plane surface (fixation point “0°” straight ahead at eye-level), the visual field with fixed eyes extended over 208° horizontally and reached from −12° to +69° vertically. The binocular visual field amounted to 67°. Eye movements of 12° (±2)° to both sides and 64° upwards could be induced. In the seal performing eye movements, a visual field of 210° in the horizontal plane and 121° to the dorsal side was determined. From the measured eye movements, a visual field of 232° in the horizontal plane appears possible.