The lesion is unilateral and there are no concurrent respiratory signs so I’m not worried about avian flu. But should I be? I’ve suggested taking a bacteriology sample and cytology swab for fungal hyphae and cryptosporidium too. Abrahams and colleagues have written a useful guide to the numerous differentials in Conjunctivitis in birds.
Vet Clin North Am Exot Anim Pract 2002 5:287-309. I’ll let you know what happens with the duck!