Betta Temporarily 'blind'

As anyone experienced the same:

I came home late today. It had been dark for a couple of hours. When I turned on the lights in the room, my betta must have been woken up. And he was swimming around the walls of the tank, and running into the wall or thermometer, as if couldn't see.

He's a perfectly healthy betta, always has a good appetite. The only time I saw him swim like that was in the 60 seconds after I switched the lights on.

 

Most likely it's because the room was dark, and they don't like sudden light changes.
I need to start waiting for the sun to light the room, and then turn the tank on.

 

Did your mother ever come into your room early in the morning, throwing open the curtains and near on burning your eyes out?

Bettas don't like it either

 

When I used to turn the light on in the morning, my angel fish would always lose his bearings and take a minute or two to relax from the sudden light change. I have since relocated my tank and positioned it next to a window. By the time I turn the light on, the sun has already risen and there is no sudden light change when turning the light on. Fish love and need routine