Corneal power and underwater accommodation in great cormorants (Phalacrocorax carbo sinensis)

In great cormorants (Phalacrocorax carbo sinensis), corneal refractive powers, determined by photokeratometry, ranged between 52.1 diopters (52.1D) and 63.2D. Photorefractive reflexes, determined by infrared video photorefraction, indicated that in voluntary dives the cormorants accommodate within 40-80ms of submergence and with myopic focusing relative to the photorefractor attained when prey was approximately one bill length from the plane of the eye. Underwater, the pupils were not constricted and retained diameters similar to those in air. These results support previously reported capacities of lenticular changes in amphibious birds yet do not fully correspond with earlier reports in terms of the coupling of iris constriction with accommodation, and time course.