I was having trouble with the sentence
because I could not understand the usage of 到 here. After I spent some time thinking I figure the meaning is that the rats were hungry to the extent that their eyes turned green (a metaphor of some sort?) but if that is indeed the case, what would you call this type of word? In English I believe the word "to" used in this way is called a preposition but I haven't seen anything online about the usage of prepositions in Chinese.