Hi, I have a 1-year old doberman which we have had since 10-weeks old. He goes mad with lights and starts to constantly chase them. He is so addicted to them he is totally oblivious to what's going on around him. He has never been teased with lights. This is becoming a major distraction especially with the summer on the way. The sun reflects off the windows and he follows it round everywhere. If we close the curtains he still keeps looking for it!
Does anyone have any advise to stop this behaviour??

Many dogs are distracted by light beams, but seldom to the extent you report. I am not sure what to suggest. Perhaps use a flashlight and let him catch a light. He may lose interest once he catches it a few times and finds it is nothing.

When he is distracted by a light you can't control, try to distract him with a toy or treat. Praise him if takes the toy or treat.

I remember taking a puppy to a meeting and it being distracted by the sun reflecting off the ceiling fan. A little patch of light kept sweeping across the floor. I think I was able to get him started on his chew toy.