Chinese Scaleless Telescope
Telescope eye goldfish were developed in China back in the early 18th century. They made their way to Japan, and were very popular within the gardens of the upper classes in both countries. Over in Japan, they became known as the Demekin, which is the name they’re still called by today. Demekin are some of the most popular fish in Japan.
As one might expect, they don’t have great eyesight. Their eyes are generally born fairly flat, with normal sight, and gradually protrude to up to 3/4 of an inch (1.9-2.0 cm) over the first six months. Telescope goldfish are pretty slow-moving and disabled, so they don’t do well with fish that have normal eyesight/normal bodies.
Goldfish Varieties and Tropical Aquarium Fishes. William T. Innes, 1917.