A fishy story about eye growth

Optometric Management, Sep 2000

We've heard about a human hand being transplanted onto a different body's arm, and we know about kidney, heart and cornea transplants. Medical technology is rapidly advancing these days, improving the quality of some lives and saving others. It almost seems as if nothing is impossible.

Well, there's been yet another development in vision research. And although it wasn't founded in humans, it provides hope that one day, it may be possible to give sight back to those who have lost or have never had it. Here's what was found.

The fish Astyanax mexicanus lives deep inside caves off the coast of Mexico where no light shines. These fish had eyes millions of years ago, but are now born without them. A different group of the same species of fish live on the surface where there is light. Aside from these different preferences in living quarters, the other difference between these fish is that while the cave-dwellers are blind, those that live on the surface develop eyes and see normally.

The mystery behind this phenomena has sparked an interesting experiment. Yoshiyuki Yamamoto of the University of Maryland and Professor William Jeffery performed tests to see what it would take to get the eyes back in the cave-dwelling fish. The pair implanted a lens from the eye of a surface-dwelling fish into its blind cousin to see what would happen.

Amazingly, an eye started developing from underneath a flap of skin on the cave-dwelling fish within 8 days. After 2 months, the cave fish had grown a large eye with a distinct pupil, cornea and iris and the retina had photoreceptor cells. Yamamoto and Jeffery reported their findings in the journal Science.

"This offers clues about what sort of molecules are involved in eye growth of any vertebrate and it shows that the growth of an eye is controlled in a large part by the lens," said Jeffery in a statement.

Although these two researchers aren't working with human subjects, their work may someday be useful to eyecare professionals in the field of blindness research.