Dictionary of Ichthyology  

bubble-eye goldfish = goldfish (Carassius auratus) having upward directed eyes accompanied by fluid-filled sacs. The fluid can be extracted for studies on its growth-promoting effects on fish cell cultures; the fluid regenerates and the fish need not be sacrificed.

Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Goldfish_Bubble_Eye.jpg .

Canadian Museum of Nature
www.briancoad.com