| Objective To explore the relationship of retinal dopamine and melanin deficiency via the refractive, retinal structural and dopamine comparison between the albino and pigmented guinea-pigs.Method Twelve albino guinea-pigs and 12 pigmented guinea-pigs of 220 grams (age of 5 week) were chosen at random. The eyes were examined with retinoscopy, A-scan ultrasonography and vernier caliper. The retinal structures were examined with light and electron microscope. The distribution of TH and dopamine D2 receptor protein in retina was observed by using light microscope. Retinal dopamine contents were quantitated by HPLC.Results The diopter is -19.17 D in albino guinea-pigs and +0.63 D in pigmented guinea-pigs on average. The average axial length is 9.30 mm in the albino and 8.60 mm in the pigmented. There are significantly statistical differences between them. Morphology changes: Albino guinea-pigs showed decreased retinal thickness, fewer pigment granules and decreased membrane disc of the outer segment of visual cells in pigment epithelial cells, and narrowed membrane disc space. Pigmented guinea-pigs showed normal retinal thickness, plenty of pigment granule and membrane disc in pigment epithelial cells, and wider membrane disc space. There is less TH protein and more dopamine D2 protein expressed in the retina of the albino than that of the pigmented. And dopamine level in the retina of the albino guinea-pigs declined. There are significantly statistical differences between them.Conclusion Albino guinea-pigs have high myopia and pigmented guinea-pigs have light hyperopia. There are differences of retinal structure between albino and pigmented guinea-pigs. The abnormity of albino guinea-pigs pigment epithelial cells is one of the key issue of the morphologic changes with its high myopia. The decline of retinal dopamine contents and the deficiency of melanin in RPE layer of albino guinea-pigs are bound up with the formation of high myopia of albino guinea-pigs.
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