The falls could affect the eye (8)
I believe the answer is:
cataract
'the falls' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for cataract that I've seen before include "Falls" , "may impair the vision" , "Drop" , "Large waterfall" , "Waterfall - opacity of the eye" .)