When you have your initial medical you are required to provide a past history of medical conditions, but I can't remember if there is a time limit, ie 5 years etc, on previous conditions.
You would be wise to declare it anyway as the CAA Medical Branch have the right to access your medical records, but they are obliged to take into account your GPs opinion, and if you haven't suffered any problems for 5 years or so, I doubt that they'd hold it against you.