We have a sliding glass door that separates the dining room from our patio. When we first moved in I would make sure that the door was always sparkling clean to allow us to have a great view of the patio and backyard. Then one day, one of our cats was running from outside and up to the glass door at full speed. I realized a split second before the cat hit the glass full on that he didn't see that it was closed. My poor kitty was dazed and had almost knocked himself out. After I checked him out and to be honest I couldn't stop laughing at what I just saw, I decided not to keep the lower part of the door quite so sparkling clean.
It was about 3 months later that I was visiting a friends home and noticed she had put new doors up to replace her old sliding glass door. She had bought these lovely Ft Myers custom doors that looked like french doors.It seems that her rather large dog had done the same thing as our cat did but he went through the glass. The dog had to have a few stitches and she told me that there was blood and glass everywhere. She decided then to not fix the sliding glass door but to replace it with a door that the dog could see.
A bit of advice here to all sliding glass door owners that have pets that go in and out the house. Either place stickers on the door at pet level or just let the glass get a little dirty so your pet can see the glass.