这是由名词 sight 加后缀 ed 变化来的。
名词 sight 的意思是“视力”，而后缀 -ed 可以接在名词后面表示“有……(having, possessing)”，所 sighted 的意思是“有视力的”（having the ability to see）：
注：sight 虽然可以用作动词，但不涉及是否有视力。
牛津词典对其动词用法的解释是：to suddenly see sth, especially sth you have been looking for 看到，发现(期待的事物)：
朗文词典对其动词用法的解释是：to see something from a long distance away, or see something you have been looking for 〔从远处或经过一番寻找后〕看见，发现
韦氏词典对其动词用法的解释是：
to see (something or someone that is being looked for or that is rarely seen or difficult to see) 看到（正在寻找或很少见到或很难见到的某物或某人）
