Do Schwann cells or Oligodendrites form the myelin sheath around the optic nerve?
Oligodendrites.
What are the 3 basic anatomic “rules” of the orientation of the nerve fibers within the optic chiasm?
- Nasal retinal fibers of each eye cross in the chiasm into the contralateral optic tract.
- Lower retinal fibers project through the chiasm to lie laterally in the optic tract; upper retinal fibers lie medially.
- Inferonasal retinal fibers cross in the chiasm but course anteriorly (~4mm) in the contralateral optic nerve (Wilbrand’s Knee).
The bulk of the blood supply to the optic nerve head is from what artery/ies?
Short posterior ciliary arteries (extension of the ophthalmic artery).
*The RNFL blood supply is derived from the CRA
What is the most common VF defect seen in someone with papilledema?
Enlarged blind spot.
*Vision is typically okay although some patients may report temporary “graying of vision” that completely resolves. Vision is usually affected in the chronic or atrophic stage of papilledema.
Does papilledema cause nerve palsies?
Papilledema may lead to an abducens palsy either unilateral or bilateral. This is due to compression of the nerve against the petrous temporal bone at the base of the skull.
Idiopathic Intracranial Hypertenison is characterized by?
- Increased incranial pressure
- Normal or small-sized ventricals on neuroimaging
- Normal CSF composition
- Papilledema
- Lack of any neurologic deficits that cannot be attributed to elevated intracranial pressure.
What percentage of patients with recent onset optic neuritis presented with optic disc edema or papillitis (according to the ONTT)?
1/3
Name 3 mimickers of Optic Neuritis and how do you distinguish them from optic neuritis?
- Nonarteritic Ischemic Optic Neuropathy - Usually seen in older patients and they do not present with pain on eye movement. They usually have other systemic conditions that predispose them to an ION.
- Leber’s Hereditary Optic Neuropathy - seen in the same age population but they lack pain on eye movement and visual recovery is poor.
- Optic Nerve Sheath Meningioma - 1/4 of these patients have optociliary shunt vessels and the disc edema typically lasts for more than 6-8 weeks.
What percentage of patients will show improvement in VA following a NAION?
46%
List some atypical features that should lead a clinician from the diagnosis of idiopathic NAION to another diagnosis…
- Patient is younger than 50
- Absence of typical risk factors - hypertension, DM, High cholesterol
- Patient has light perception (typically NAION causes decreased vision between 20/25-20/200)
- Ant/Posterior cells
- No visual improvement after 3 mos.
List some differential diagnosis if the patient presents with atypical characteristics of a ION.
AION, Optic Neuritis, LHON, Sarcoidosis, Infiltrative optic neuropathy (leukemia, lymphoma), Compressive optic neuropathy (Optic nerve sheath meningioma)
List some ways to differentiate ION with optic neuritis
Age of patient, pain on movement (67% with ON, 8% with ION), VF defect (central scotomas in ON, Altitudinal in ION), VA recovery, MRI of orbit (shows thickening in ON)
What are some common systemic symptoms of a patient with GCA
Jaw pain while eating, headache, polymyalgia rheumatica, scalp tenderness, anorexia, weight loss, fever
50% of optic nerve gliomas in children are due to what systemic condition?
Neurofibromatosis
How far (in mm) must a pituitary adenoma grow before it starts to compress the visual system?
~10mm.
What is pituitary apoplexy?
Sudden expansion of an existing pituitary adenoma due to intratumoral hemorrhage or infarction.
What is the order of involvement of the rectus muscles affected in Thyroid-Related Orbitopathy?
Inferior - Medial - Superior - Lateral
List some Non-thyroid causes of extraocular muscle enlargement
- Inflammatory: Sarcoid, Wegener’s, Crohn’s, Whipple’s, SLE, RA, Idiopathic Orbital Inflammation
- Vascular: CCF, AV Malformation
- Neoplastic: Local or Metastasis
- Infectious: Viral, bacterical, fungal, parasitic, Orbital Cellulitis
- Deposition: Amyloid
- Traumatic
- Iatrogenic: Following orbital/sinus surgery. Drug Induced - lithium, chloroquine
- Congenital: Fibrosis syndromes, NF
- Miscellaneous: Acromegaly, Vit E deficiency
List some ophthalmoscopic features seen in patients with pseudopapilledema
- Elevated disc; obscured margins
- Absence of central cup
- Vascular anomalies with increased branching
- Normal NFL; disc transilluminates
- Presence of a SVP is strongly suggestive of pseudopapilledema
- Hyaline bodies
- Hyperopia
- Small scleral canal
- Non-hyperemic disc
- No Hemes, Exudates, CWS
What is the most frequent cause of pseudopapilledema?
Optic Nerve Head Drusen
- 75% are bilateral
- Seen in predominately caucasians
- Lumpy-Bumpy appearance
- SVP often present
- Occasionally associated with hemorrhages
- Up to 73% with visible drusen have a VF defect with slow rate of progression - most often the loss is nasally.
- May cause subretinal, intraretinal hemorrhages or peripapillary choroidal neo.
What syndrome is characterized by panhypopituitarism, BONH (bilateral optic nerve hypoplasia) and midline brain abnormalities?
De Morsier’s - occurs in ~10% of children with BONH
What funduscopic finding is reported in children of insulin-dependent diabetic mothers?
Superior segmental optic hypoplasia
- Superior entrance of the CRA
- Pallor of superior disc
- Superior peripapillary halo
- Thinning of the superior RNFL
What is the proposed origin of retinal edema seen in optic nerve pits?
Vitreous or CSF
Astrocytic Hamartomas are large, multilobulated deposits on the surface of the disc or retina and are commonly seen in patients with what systemic condition?
Tuberous Sclerosis - multi-system condition where non-malignant tumors grown in various organ systems.
*Less frequently seen in neurofibromatosis
