The African Eagle Owl has a persistent ptosis (lowered eyelid). What might cause this and what diagnostic test could you use to confirm your diagnosis?
Ptosis can be caused by facial nerve damage or Horner’s syndrome, since the upper eyelid is partially sympathetically innervated. Using 0.1% phenylephrine will imrpove the ptosis as seen here. We might also expect miosis (lack of sympathetically-innervated pupil opening) and enophthalmos (lack of functional innervation of the peribulbar muscle come) but in birds the iris is striated muscle and thus not autonomically innervated and in an owl like this the globe is conical to enophthal;mos does not occur. Read more about Bubo, this owl in our paper ‘Horner’s syndrome in an African spotted eagle owl (Bubo africanus.’ Veterinary Record 134:64-6