-1.5 is mild shortsighted so you should be able to read without them.
With them off you will have better contrast, especially if they are dirty or you are using a computer screen.
But if you are anything like me you will break them more by taking them off.
Go with whatever is most comfortable for you when you read. If taking them off makes it easier to read, take them off. If leaving them off makes things look a bit blurry and you start getting headaches or have trouble seeing the text, put them back on.