Electron microscopic studies on celestial goldfish retina—A possible new type of retinal degeneration in experimental animals

Abstract

The celestial goldfish (Carassius auratus) is one of the varieties of telescopic-eye goldfish, and a product of artificial selection. Their eyes are soft and telescopic anterior to dorsal. Abnormally thin retinas of celestial goldfish have only a small number of photoreceptor cells, and show various stages of retinal degeneration. The outer segments are short and markedly disorganized or often missing. Macrophages lies close to the outer or inner segments in single or clumped states, and sometimes replace the photoreceptor layer and/or the pigment epithelial layer. In a highly degenerated retina, the macrophages migrate to the inner layers or to around retinal vessels on the vitreous surface of the retina. The morphology of the celestial goldfish retina is regionally highly variable and also varies greatly between individuals. It is possible that this is a new type of primary retinal degeneration in experimental animals, although accompanying ocular enlargement.