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 degrees" straight ahead at eye-level), the visual field with fixed eyes extended over 208 degrees horizontally and reached from -12 degrees to +69 degrees vertically. The binocular visual field amounted to 67 degrees. Eye movements of 12 degrees (+/-2) degrees to both sides and 64 degrees upwards could be induced. In the seal performing eye movements, a visual field of 210 degrees in the horizontal plane and 121 degrees to the dorsal side was determined. From the measured eye movements, a visual field of 232 degrees in the horizontal plane appears possible.