"Why does the eye see a thing more clearly in dreams than the imagination when awake?"

I don't have the right answer for you question, but that's my point of view .. a dream is still an imagination, but in a sub-conscious way .. probably because wile you're awake, your brain is focusing on more stuff, thinking process, all your senses (see, smell, touch, taste, hear) and many more .. while when you're sleeping the brain could be more focusing on the thinking process which creates the dreams .. I could be wrong though, but as i said that's how i see it .... but for me, dreams and imagination are both clear and sharp

Well point to be noted . There are better cameras available in market as compared to eye. Hope this may answer your question