1. Neuro-Ophthalmic Diseases
1.1. **Facial Nerve Paralysis**
1.2. Horner's Syndrome
1.2.1. Loss of sympathetic innervation to the eye and adnexa.
1.2.2. Clinical signs include miosis, enopthalmos, protrusion of the third eyelid, and ptosis.
1.2.3. Diagonostic pharmacologic testing may help localize the lesion if postganglionic.
1.2.3.1. **Phenylephrine** 1% ophthalmic solution is a **direct sympathomimetic**.
1.2.3.1.1. **Quicker than normal mydriasis if the lesion is in post-ganglionic because of denervation hypersensitivity** - increased number of receptors or lack of degredation of neurotransmitter in face of insufficient neurotransmitter.
1.2.4. Treatment of underlying cause if known; prognosis is dependent on the underlying cause.
1.3. **Optic Nerve Atrophy, Hypoplasia, & Coloboma**
1.3.1. Optic Nerve Atrophy
1.3.1.1. Degeneration of the optic disc due to degnerative changes in retinal ganglion cells, resulting in visual deficits and PLR abnormalities.
1.3.2. Optic Nerve Hypoplasia
1.3.2.1. Small remnant of the optic disc present. Hereditary; decreased number of retinal ganglion cells/optic nerve axons,
1.3.3. Optic Nerve Coloboma
1.4. **Optic Neuritis**
1.4.1. Inflammation of the optic nerve.
1.4.1.1. Clinical signs include acute vision loss, dilated pupil, and raised, swollen optic disc with blurred margins.
1.4.1.2. Numerous causes, including infectious, inflammatory, traumatic, neoplasia, and toxic.
1.4.1.3. Diagnosis made with clinical signs, concurrent CNS signs, and MRI.
1.4.1.3.1. Differential diagnoses include glaucoma, retinal detachment, and SARD.
1.4.1.4. Treatment with systemic steroids; prognosis is poor for vision and life.
1.5. **Granulomatous Meningoencephalitis**
1.5.1. Autoimmune disorder in which inflammatory cells proliferate in the CNS and form granulomas.
2. Sympathetic Innervation of the Eye and Adnexa
2.1. 1st Order Neuron
2.1.1. Begins in the hypothalamus and travels through the brainstem to the lateral tectogmental spinal tract.
2.1.1.1. Development of 1st order lesions is unlikely in the absence of thalamic, brainstem, and myelopathic deficits.
2.2. **2nd Order Neuron**
2.2.1. Begins with gray matter of the first three thoracic spinal cord segments (T1-T3), continues through the ramus communicans, and travels through the thorax with the sympathetic trunk. Travels through, but does not synapse with the cervicothoracic and middle cervical ganglia.
2.2.1.1. Close anatomic structures include the brachial plexus and carotid artery.
2.3. **3rd Order Neuron**
2.3.1. Axons exit the cranial cervical ganglion, form plexus around carotid, become nasociliary nerve, long.....
2.3.1.1. Close anatomic structures include the middle ear and guttural pouch in horses.
2.3.1.2. The path of the 3rd order nueron is not well defined.