Hi Mazo,
I'm a fellow birdshot sufferer in the UK. I suggest you post this question to the Birdshot.org site. It's the site for UK sufferers. Annie and Rea who run it are pretty on the ball and would probably know. Also there is a patients' day at Moorfields eye hospital (London) just for sufferers of the condition on September the 11th. Apologies if you already know about this and the birdshot site
Cheers
Adrian