Postnatal maldevelopment of the retina.

The effect of certain factors on the early postnatal development of the retina was studied by electron microscopy. Although the retina of developing rats injected with sodium iodate on the 1st and 7th postnatal days showed no retardation of development of photoreceptor outer segment, it began to degenerate about 3 weeks after birth. The retina of developing rats exposed to strong light from the 1st to 5th postnatal day revealed slight developmental retardation of the photoreceptor outer segment and the photoreceptor outer segment began to degenerate about 3 weeks after birth. The vitamin A deficient developing rat it began to degenerate nearly 3 weeks after birth. In spite of induction of developmental retardation of the photoreceptor outer segment of the retina, development of the photoreceptor outer segment was not completely inhibited by moderately acting factors. However, 3 weeks after birth, the photoreceptor outer segments began to degenerate. Therefore, some factors during the early postnatal period can cause the late appearance of degeneration of the retina. The characteristics of retinal degeneration are the same as those found in the retinas of adult rats which are affected by each factor. These degenerations later recover morphologically.