Does anyone know why I see an orange spot when I first wake up?

When I wake up usually from a nap I see orange in the center of my vision for a few seconds and it slowly fades away. I recently was prescribed eye glasses for computer use so I use them at home. I noticed when I nap after work I wake up and feel like I am looking out of my glasses for a few seconds. I was told it was my eyes dialating because they are used to my glasses for hours. But what is up with the orange spot?