have and eye on，have an eye to，have an eye for
这三个短语的涵义各不相同，不能互换使用。
Have an eye on是照顾、留意、监视，它与keep an eye on同义，可互换使用。例：
Please have（keep）and eye on my child while I am away．
我不在的时候，请看管一下我的孩子。
You must have（keep）an eye on that loan shark．
你必须监视那个大耳窿的活动。
have an eye to是有欲得的愿望。例：
All these countries have an eye to this island as it is rich in oil．
所有这些国家都想夺取这个岛屿，因为它盛产石油。
Since he joined the company，he has had an eye to its financial interests and assets．
自从加入了该公司，他就觊觎公司的财务权益及资产。
Have an eye for的意思是对有眼力、有识别的能力。例：
This old man has an eye for curios．
这个老大爷有辨别古董的眼力。
All the police dogs trained have an eye for drugs．
所有受过训练的警犬都有识别毒品的能力。