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Questions and Answers
What is the primary consequence of disc hemorrhages on myelin?
What is the primary consequence of disc hemorrhages on myelin?
What is the most common type of ischemic optic neuropathy?
What is the most common type of ischemic optic neuropathy?
What is the primary cause of Non-Arteritic Ischemic Optic Neuropathy (NAION)?
What is the primary cause of Non-Arteritic Ischemic Optic Neuropathy (NAION)?
What is the most common symptom of compressive optic neuropathy?
What is the most common symptom of compressive optic neuropathy?
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What is the significance of optociliary shunt vessels in the optic disc?
What is the significance of optociliary shunt vessels in the optic disc?
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What is the primary goal of diagnosing and treating compressive optic neuropathy?
What is the primary goal of diagnosing and treating compressive optic neuropathy?
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What is the average age of onset for patients with NAION?
What is the average age of onset for patients with NAION?
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What is the primary cause of AAION?
What is the primary cause of AAION?
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What is the characteristic of the disc in the fellow eye of a patient with NAION?
What is the characteristic of the disc in the fellow eye of a patient with NAION?
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What is the typical treatment for AAION?
What is the typical treatment for AAION?
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What is the pathophysiological process underlying AION associated with Sarcoidosis?
What is the pathophysiological process underlying AION associated with Sarcoidosis?
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What is the most common symptom of AAION?
What is the most common symptom of AAION?
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What is the approximate number of nerve fibers present in each human optic nerve?
What is the approximate number of nerve fibers present in each human optic nerve?
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What is the function of the optic chiasm?
What is the function of the optic chiasm?
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Which part of the retina lacks photoreceptors resulting in the eye's blind spot?
Which part of the retina lacks photoreceptors resulting in the eye's blind spot?
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What is the final destination of the nerve fibers in the optic pathway?
What is the final destination of the nerve fibers in the optic pathway?
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Which meningeal layer is the outermost layer that ensheathes the optic nerve?
Which meningeal layer is the outermost layer that ensheathes the optic nerve?
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What type of signals are transmitted through the optic nerve?
What type of signals are transmitted through the optic nerve?
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What is the characteristic of reduction in contrast sensitivity in compressive optic neuropathy?
What is the characteristic of reduction in contrast sensitivity in compressive optic neuropathy?
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What is the most common cause of traumatic optic neuropathy?
What is the most common cause of traumatic optic neuropathy?
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What is the characteristic of infiltrative optic neuropathy?
What is the characteristic of infiltrative optic neuropathy?
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What is the treatment for traumatic optic neuropathy?
What is the treatment for traumatic optic neuropathy?
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What is the characteristic of compressive optic neuropathy?
What is the characteristic of compressive optic neuropathy?
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What is the cause of papilledema?
What is the cause of papilledema?
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What is the characteristic feature of Terson syndrome?
What is the characteristic feature of Terson syndrome?
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Which of the following is NOT a common symptom of cerebral venous sinus thrombosis?
Which of the following is NOT a common symptom of cerebral venous sinus thrombosis?
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What is the typical pupillary response in AION?
What is the typical pupillary response in AION?
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Which of the following conditions is commonly associated with loss of consciousness?
Which of the following conditions is commonly associated with loss of consciousness?
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What is the significance of fundoscopic examination in AION?
What is the significance of fundoscopic examination in AION?
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Which of the following is a common feature of papilledema?
Which of the following is a common feature of papilledema?
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Study Notes
Optic Nerve Anatomy
- The optic nerve is the second of twelve paired cranial nerves.
- Each human optic nerve contains 1.2 million nerve fibers.
- These fibers are axons of the retinal ganglion cells of one retina.
- The optic nerve is ensheathed in all three meningeal layers (dura, arachnoid, and pia mater).
- The optic nerve leaves the orbit (eye socket) via the optic canal, running postero-medially towards the optic chiasm.
- In the optic chiasm, there is a partial decussation (crossing) of fibers from the temporal visual fields (the nasal hemiretina) of both eyes.
Optic Nerve Physiology
- Light stimulation of the retina travels via the optic nerve as electrical signals to the visual cortex and is ultimately interpreted as visual images.
- The eye's blind spot is a result of the absence of photoreceptors in the area of the retina where the optic nerve leaves the eye.
- Symptoms of optic neuropathy include:
- Reduction in visual acuity
- Reduction in color vision
- Reduction in contrast sensitivity
- APD (afferent pupillary defect)
- Associated ocular inflammation (iritis, vitritis, pars planitis, intermediate uveitis) can be present depending on the etiology
Infiltrative Optic Neuropathy
- Causes:
- Tumors (intra-cranial, chiasmal, or optic nerve tumors)
- Non-neoplastic lesions (retrobulbar hemorrhage, aneurysm, mucocele, orbital apex syndrome)
- Compression can be unilateral or bilateral
- Treatment: directed at the underlying cause
Traumatic Optic Neuropathy
- Classically divided into:
- Direct injury: external object penetrates the tissues and impacts the optic nerve
- Indirect injury: collision to the skull and the energy is absorbed by the optic nerve
- Causes:
- Motor Vehicle Accident (MVA), most common cause
- Bicycle Fall
- Assault
Papilledema
- Bilateral disc swelling due to increased intracranial pressure
- Causes:
- Primary and metastatic intracranial tumors
- Hydrocephalus
- Pseudotumor cerebri: often occurs in young, overweight females
- Subarachnoid hemorrhage: severe headache, may have preretinal hemorrhages (i.e., Terson syndrome)
- Arteriovenous malformation
- Brain abscess: often produces high fever
- Meningitis: fever, stiff neck, headache
- Encephalitis: often produces mental status abnormalities
- Cerebral venous sinus thrombosis
Ischemic Optic Neuropathy
- Non-Arteritic (NAION) 95%:
- Cause: Hypoperfusion or Non-perfusion of the optic nerve head
- Risk factors: Diabetes mellitus, Hypertension, Hypercholesterolemia, Smoking
- Arteritic (AAION) 5%:
- Cause: Vasculitis of the short posterior ciliary vessels supplying the optic nerve head leading to ischemia
- Associated with giant cell arteritis
- Mean age of onset: 70 years
- Symptoms: Severe visual loss, developing over hours to days
Management
- Treatment should be directed at the underlying cause of the increased intracranial pressure
- NAION: observe, control risk factors
- AAION: high-dose (steroid) oral prednisone or intravenous methylprednisolone followed by a course of oral prednisone
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Description
Test your knowledge of the optic nerve, including its anatomy, structure, and function. Learn about cranial nerve II, the optic canal, and the meningeal layers. Assess your understanding of the optic nerve's role in vision.
