I am not a big fan of Slabodka style mussar, but if you go for that sort of stuff: Rashi explains that Yitzchak's eyesight became poor in his old age (27:1) due to his exposure to the irritating fumes of burning incense offered by Eisav's wives to worship their avodah zarah (parenthetically: this suggests that avodah zarah was taking place right under Yitzchak's nose -- did this not reflect on Eisav and warrant a reaction of some sort?) But why did these fumes only affect Yitzchak's eyesight? Would they not also have affected Rivka's eyesight as well? The Sifsei Chachamim answers (citing Maharashal) that Rivka was less sensitive to the fumes and smoke because she grew up in a house where she had been exposed to avodah zarah and was used to its affects.
Let's put this in context (my wife gets credit for this observation): Rashi tells us that Yitzchak was 123 when he decided to bless Eisav. Recall that according to Rashi (25:20) Yitzchak was 37 years older than Rivka, meaning Rivka would have been 86 years old. Furthermore, according to Rashi Yitzchak married Rivka when she was just three years old. So here we have an elderly Rivka, a woman who has spent the past 83 (!) years wed to a tzadik like Yitzchak, a woman who abandonded her own home with its idolatry at the tender age of only three, a woman who was observed by Yitchak to have the same midos and purity as his mother Sarah before marriage. Yet because she "grew up" more than 83 years ago in a house where avodah zarah was worshipped, she had a lesser sensitivity to avodah zarah than Yitzchak! How could that be?
The Slabodka mussar ending: we see from here how deep and indelibe every impression is, how what we expose even a little child to can leave a mark that years of tzidkus and taharah cannot completely undo. Etc. etc. (Sorry, I have no aspirations to be a mashgiach. My son has asked me why in yeshiva he has to give up time from learning to listen to the mashgiach's shmooz -- I told him he should ask his rebbe.)