Contact lenses are blurry, normal?

Well i got my contact lenses a week ago and have been wearing them everyday for around 5-7 hours. Everything is clear and crisp in the daylight but when i'm in a dark area or when its night time its all very blurry and its just hard to see. I can see but its blurry. My optician said that its normal and you cannot change it but i have been visiting a few sites and saw that its the brand that needs changing. My optician recommended me proclear toric xl or xr the ones you change each month. So i dont really know what to do my prescription is -8.50 in both eyes which means i'm very shortsighted. Any help? I asked this question and someone goes that it's weird that it happens but my optician says you cannot change it all?

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