Howland H C, Sivak J G
Vision Res. 1984;24(12):1905-9. doi: 10.1016/0042-6989(84)90024-5.
Refractive states measured by retinoscopy and photorefraction indicate that rockhopper (Eudyptes crestatus), Magellanic (Spheniscus magellanicus) and gentoo (Pygoscelis papua) penguins are approximately emmetropic in air and water. Extensive myopia in air, as predicted by early authors, is nonexistent. Photorefractive measurements of refractive state in water indicate that rockhopper, gentoo, Magellanic and king (Aptenodytes patagonica) penguins can accommodate sufficiently to make up for the loss of refractive power of the cornea. Corneas of rockhopper and Megellanic penguins are flattened relative to the overall size of the eye. This feature minimizes the optical effect of submergence.
通过检影验光和 photorefraction（可能是“ photorefractometry”，验光仪测量法）测量的屈光状态表明，跳岩企鹅（Eudyptes crestatus）、麦哲伦企鹅（Spheniscus magellanicus）和巴布亚企鹅（Pygoscelis papua）在空气中和水中大致为正视眼。早期作者所预测的在空气中的高度近视并不存在。在水中对屈光状态的验光仪测量法表明，跳岩企鹅、巴布亚企鹅、麦哲伦企鹅和帝企鹅（Aptenodytes patagonica）能够充分调节以弥补角膜屈光力的损失。相对于眼睛的整体大小，跳岩企鹅和麦哲伦企鹅的角膜是扁平的。这一特征将浸没的光学效应降至最低。
