The developmental changes of ERGs on spontaneous retinal degeneration of Celestial goldfish

The Celestial goldfish, which belongs to the family of telescope-eye goldfish, displays unique spontaneous retinal degeneration associated with developmental anterodorsal protrusion of the eyeball. We observed concurrent changes in the electroretinogram. At the age of 75 days, the retinal layer was developed fully and the electroretinogram exhibited b-wave dominance similar to that of adult common goldfish. At the age of 105 days, when the eyeball began to protrude laterally, the b-wave amplitude decreased to 52% of its earlier developmental stage, with a prolonged peak time. Histologic change was observed in the retinal pigment epithelium and photoreceptor layers. At the age of 135 days, when the eyeball protruded further anterodorsally, the histologic changes extended to all retinal layers and the ERG b-wave was extinguished. Electrophysiologic and histologic changes in the Celestial goldfish eye were found to be proportional to the grade of eye protrusion. Since similar goldfish do not show these changes, however, the Celestial goldfish may be a new model of hereditary retinal degeneration.