Sivak J, Howland H C, McGill-Harelstad P
Proc R Soc Lond B Biol Sci. 1987 Jan 22;229(1257):467-72. doi: 10.1098/rspb.1987.0005.
Refractive states measured by retinoscopy and photorefraction indicate that the eyes of the Humboldt penguin, Spheniscus humboldti, are approximately emmetropic in air and water. Extensive myopia in air, as predicted by earlier authors and by a recent anatomical study, is non-existent. Photorefractive measurements of the refractive state, in water, of the Humboldt penguin indicate that it can accommodate sufficiently to make up the loss of the refractive power of the cornea. The cornea of the Humboldt penguin is flattened relative to the overall size of the eye. In all these respects (corneal flattening, and accommodation in air and water) the eyes of Humboldt penguins are like those of gentoo, (Pygoscelis papua), rockhopper (Eudyptes crestatus), Magellanic (Spheniscus magellanicus), and king penguins (Aptenodytes patagonica).
通过检影验光和 photorefraction 测量的屈光状态表明，洪堡企鹅（Spheniscus humboldti）的眼睛在空气和水中大致为正视眼。早期作者和最近的一项解剖学研究预测的在空气中的高度近视并不存在。对洪堡企鹅在水中屈光状态的 photorefraction 测量表明，它能够充分调节以弥补角膜屈光力的损失。洪堡企鹅的角膜相对于眼睛的整体大小是扁平的。在所有这些方面（角膜扁平以及在空气和水中的调节），洪堡企鹅的眼睛与巴布亚企鹅（Pygoscelis papua）、凤头黄眉企鹅（Eudyptes crestatus）、麦哲伦企鹅（Spheniscus magellanicus）和帝企鹅（Aptenodytes patagonica）的眼睛相似。
