In its earliest stages, retinopathy often has no overt symptoms but can progress over time to a phase in which the blood vessels of the eye leak and rupture easily, eventually causing blindness.

在疾病早期，视网膜病没有明显的症状，但是随着时间的推移能进展到一个阶段：眼血管渗漏断裂，甚至致盲。

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He next plans to use lab-made tissue and see if he can successfully treat a degenerative, blindness-causing eye disease in monkeys.

WSJ: Experiment Brings Human Cloning One Step Closer