One of the things I learned today that my eyes have changed, I have worn glasses since I was about 18 years old. I have always found that when peeking through the view finder my glasses get smeared or worse moved aside. The Canon EOS 450D (in fact I think most Canon Camera’s) has a Dioptric View Finder adjustment. This is a small wheel just to the right of the view finder. Adjusting this mean I do not need to wear my glasses to look through the view finder.
To adjust it correctly set your camera preferably on tripod or on a stable surface like a wall and use AF to focus on an object, once it is in focus remove your glasses and then adjust the Dioptric Wheel until the view finder image is clear.
More info including Dioptric lenses can be found on Creative Karma