I second JB1105's recommendation. Both are great sites with lots of experienced CPAP users giving out some great advice. I also participate in the www.apneasupport.org site.
One of the more common reasons given for swollen eyes is an air leak. This also means that the pressure is not optimal, and he's not getting the full amount of air pressure into his lungs. Another reason is pressure by the mask on the face, preventing venous outflow from the eyelids. Loosening (not too much to cause a leak) the straps is one option, and another option is to change masks. If he's only recently started using the mask, I would give it some more time to get used to. If it's not improved, talk to your durable goods equipment company or your sleep doctor.
Check out the message boards on these 2 websites for CPAP related questions. The boards here are very active. I think I've read this problem on those boards before.