Optic Neuropathies Flashcards
Does optic nerve belong to CNS or PNS?
CNS
Where does myelination of optic nerve normally happen?
Post lamina cribrosa
Congential optic neuropathies
Size, orientation, drusen, closure defects, vascular abnormalities
Involutional ON
Mitochondrial
Vascular collapse
Sutrcture/mechanical ON
Due to truama
Intracranial HTN
Circulatory ON
- ischemic optic neuropathy: NAION, AION, DION
- stagnant hypoxia: CRAO
Infections/inflammatory ON
Infection
AI
Demyelination disease
Congential hypoplasia of the ONH profile
Most common congential defect
Assocaited with a Tehran alcohols use, infection ,drug use, diabetes, pituitary and intracranial abnormalities
Pathophysiology of congential ONH hypoplasia
- primary failure of the retinal ganglion cells
- DM/DD ratio >3.2 (normal 2.1-3.2)
- mutations on some genres
DM/DD ratio
DM-distance from macula to temporal edge of ONH
DD: disc diameter
Ratio of the disc diameter to the distance from the center o the macula to the temporal edge of the disc
Presentation of congential hypoplasia of ONH
- reduced VA, etc
- double ring sign: due to glial replacement tissue filling the gap between the scleral opening and the small nerve
Superior segmental optic nerve hypoplasa
Causes inferior VF defect
- sometimes hard to see
Septo-optic dysplasia (de Morsier sybdrome)-congential ONH hypoplasia
Midline dysgenic resulting in loss of septum pellucidum, pituitary abnormalities, optic disc hypoplasia
-isolated venous toruosity (no DM or microvascular disease to cause it)
Megalopapilla-congenital neuropathies
- excess of non-neural glial tissue beceoms invaginated into the optic cup during development
- large scleral foramen
Megalopapilla presnetaionts
- the disc may appear to have a large CD ratio
- DM/DD ratio is less than 2
Myelination at optic disc-congenital neuropathies
The oligodendrolglia myelinate the optic nerve a process which usually ends at the lamina cribrosa but occasiaonly extends into the visual retina. There maybe an unmyelinated area between the disc and the myelinated fibers
-VF depression
Disc drusen-congential neuropathies
- usually not clinically apparent until early adulthood
- usually bialteral
- small scleral opening is the primary cause. Nerves become crowded when passing through. The metabolic activities get affected and there will impaired axonal transport
- disc drusen are the result of axoplasmic derivatives from disintegrating nerve fibers. Extruded mitochondria and debris are prone to calcification
Fundus exam of disc drusen
- elevated disc
- deflection of the vessels
- the NFL is not edemtaous and the vessels do not show the degree of congestion and stasis that would be expected with true edema
- the ILM is wrinkled due to the stretch effect assocaited with the elevation of the disc
Typical appearance for disc drusen
Lumpy bumpy
Progression of disc drusen
- visible disc drusen are rare in children. Most cases present with elevated discs and buried disc drusen
- there is not a consistent relationship between the VF defect and the location of visible drusen
Disc drusen complications
Peripapillary hemorrhages which may extend towards the macula
In severe cases, arterial and venous shunts form and to the choroidal circulation may develop
Diagnosis of disc drusen
B scan echography most reliable
VF defect and disc drusen
Disc drusen May present with a variety of VF defects
Managment of disc drusen
- if no VF defect: yearly routine exams including IOP and VF screening
- if VF defect, then serial IOP, VF, OCT every 6 months
- if IOP is borderline, or progressively VF defect, then consider ocular antohypertensive therapy
- treat paeripapillaryu CNVM if it occurs
Incompletely closure of the optic disc
Cavitary sybdrome
- Coloboma
- Morning glory
- Optic pit
Misaligned closure of the ONH
Tilted disc syndrome
Optic pit
Cavitary syndrome: coloboma
Incomplete closure of the optic cup
-usually inferiorly
Presentation of coloboma ONH
- poor VA
- unilateral or bilateral
- double disc appearance
- often associate with staphyloma
- maculoschisis, serous macular detachment, peripheral retinal detachment
Morning glory disc
- more common in females
- unilateral more often
- associated with craniofacial disorders, pituitary defects, cerebrovacualr abnoraliesi
- variant of coloboma
- often asymptomatic: 25-75% risk fo serous macula detachment
MGD compared to Coloboma
- less assocaited with systemic problems
- more common in females and more common in whites
- characterized by a funnel appearance and abnormally straightened vessels
Intracranial abnormalities in morning glory disc
Problems with cerebral arteries
Optic pits
- focal defects at level of lamina cribrosa
- variant of coloboma
Presentation of optic pits
Visual acuity is typically normal
Serous macular detachments and/or maculoschisis occur in 30-50% of pits most often between ages 20-40
-mostly inferiortemproal with hyper pigmentation adjacent to the pit
Tilted disc
- also-aligned closure of the embryonic optic fetal fissure
- abnormal axial length
- sometimes associated with astigmatism, vascular abnormalities
- complications are serous macular detachment and CNVM
