Reading in dim light can eventually impair your eyesight.
in (into, in, on, upon)#peior (worse) (Latin)
beleaguer, hamper, impair, scuttle, thwart, undermine
Opposite of Repair. Repair is to mend, Impair is to Injure. im+pair. If you damage a pair of something. you seperate them. so you injure them.