Exophthalmos may be an initial clinical sign in horses with orbital ne
oplasms.Neuroendocrine tumors can develop in the retrobulbar space. Di
agnosis depends on demonstration of neurosecretory granules by means o
f Grimelius' or immunohistochemical staining or electron microscopy. O
rbital exenteration is the treatment of choice for orbital neuroendocr
ine tumors in horses and may result in long-term survival. Manipulatio
n of neuroendocrine tumors during surgery may cause hypotension.