The Glaucoma Research Foundation's website suggests several resources to help find a good glaucoma specialist. It recommends consulting the American Academy of Ophthalmology, American Glaucoma Society, American Optometric Association or American Board of Medical Specialties for referrals.
The American Academy of Ophthalmology has an online directory of practitioners that you can search by specialty. The American Glaucoma Society also has an online directory of members, all of whom specialize in glaucoma and received specialized glaucoma training.
The American Optometric Association can refer you to your state's optometric association, which can help you find a good specialist. Finally, the American Board of Medical Specialties can verify that a doctor has passed a board exam for the specialty, but it does not guarantee that the doctor is good.