In another post oopsorganist asked this question. In my case I have lost hearing in my right ear but I do not think it is because I have played the organ for so many years. It is just anno domini! The thought of life without music is unbearable so I have hearing aids. This at least spares me from having an operation. However I found that wearing the aids at choir practice was a disaster as I could hear everyone talking at once! In fact I do not seem to need them at church at all except for the homily if one of the speakers is not working. There was a survey done about this matter some years back and I offered to take part but heard nothing more. Anyone know the results?
I think it is highly unlikely that playing the organ could affect your hearing. As my regular job I have been tuning pipe organs almost every week for the last thirty eight years which means being very close to quite loud sounds and pitches of high frequency and I do not appear to have suffered any hearing loss (yet!!)
Forgive me Nick, but I now have this image of a man dressed in dentists' garb and mask tuning his harpsichord with a dental drill. Unsettling imagery at best I'm sure you'll agree.