![]() From here the pupillomotor fibers enter the cavernous sinus and join the trigeminal nerve, pass through periorbita and enter the globe via the long ciliary nerve. Within the middle ear the sympathetic fibres join a branch of the glossopharyngeal nerve and cross the middle ear. At the level of T1 to T3 the nerve leaves the spinal cord, extends along the thoracic sympathetic trunk and synapses in the cranial cervical ganglion near the tympanic bulla. The sympathetic nerve fibres arise from the hypothalamus, pass through the brainstem and follow the cervical spinal cord to synapse with preganglionic cell bodies in the gray matter. Horner's syndrome is caused by an affection of the sympathetic nerve. In most breeds a congenital malformation of the drainage angle is present (goniodysgenesis) with further clogging of the angel with age. Several breeds may be affected, including the American Cocker Spaniel, Basset Hounds, Samoyed, Welsh and English Springer Spaniels, Bouvier des Flandres, Siberian Husky and Norwegian Elkhound. Primary glaucoma is a breed related disease, with bilateral clinical manifestation occurring in middle aged to older dogs. Examination of the oral cavity should always be performed in dogs with space-occupying orbital lesions. ![]() Orbital ultrasound is useful in diagnosis, preferably combined with a fine-needle aspirate. In contrast, in glaucoma the globe itself is enlarged and the increase in intraocular pressure is usually more significant, the exception being concurrent uveitis where the intraocular pressure may be reduced even in buphthalmic eyes. Venous compression may lead to slightly elevated intraocular pressure in neoplasia-induced exophthalmos. Exophthalmos caused by orbital neoplasia must be distinguished from buphthalmos caused by glaucoma. Neoplasms are not initially painful, in contrast to orbital inflammatory disease. Lateral deviation is most frequent, most often with a concurrent protrusion of the third eyelid. ![]() Unless the tumor is positioned straight behind the globe, a deviation of the eye may be noted. Orbital neoplasms cause slowly progressive exophthalmos. In comparison, orbital abscesses most commonly occur at a younger age, with a mean age of about 4 years. Orbital neoplasms in general occur in older animals, the mean age being approximately 9.5 years. Thus, it is important to identify and treat underlying conditions if present, and a general examination should always be included in the work-up of an ocular condition. Ocular disease in the aging dog may be divided into primary ocular disease, and ocular signs of systemic disease. The animals' quality of life relies in part on our skills in identifying and treating these conditions. Older animals may suffer from ocular conditions that may be of slight discomfort, painful or vision threatening. ![]()
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