Don't worry, its normal for IRNs pupils to dilate. Its a sign of many things. Excitement, anger, enjoyment.. I think your IRN is enjoying his/her food!
When a birds pupils dilate its called 'pinning' or 'flashing' when they flash.
Its sometimes usefull to understand a birds body language to better understand their moods.
Alot of us here leave our birds out all day. But its a good idea to make your home as 'bird proof' as possible. Meaning removing or fixing anything that could harm your bird. They are inquisitive and can get into all sorts of trouble. My 2 naughtys raid my kitchen when I'm out of the room!
Your IRN might be calling you back. Birds are attention seekers.
Lauren