When I refresh the page it duplicates a image

Hello everybody. I am a new user of CodeIgniter and I am having a problem after uploading a image. 
I need to upload a file and everything is fine. After I upload the file I get redirected to a success page. But if I refresh (F5) this page, the image is duplicated in the folder. As I am renaming it, it never will get the same name, so I can not "override" the image. I have already tried to "unset($imageUploaded)" after I upload it, but it did not worked.
Anyone has any idea abut how to solve this problem? 
Thanks, Alfredinho.