60 Questions
Which structure is considered the anterior limit of the optic nerve?
The optic papilla
Where do the majority of canine retinal ganglion cell (RGC) axons ultimately project to?
The lateral geniculate nucleus
What is the role of intrinsically photosensitive, melanopsin-containing RGCs?
Regulation of circadian rhythms
How are the nasal and temporal halves of the retina divided in carnivores?
By the vertical meridian
Where do the RGC axons from the nasal retina cross?
At the optic chiasm
What is the vulnerability of the optic nerve attributed to?
Its concentration of axons
What is the longest region of the optic nerve called?
The retrobulbar, orbital segment
What is the anterior-most part of the optic nerve called?
The optic papilla
What is the cellular component that predominates in the optic nerve?
Astrocytes
Where does myelination of the canine optic nerve typically occur?
In the lamina cribrosa
Which type of diseases can affect the optic nerve in dogs?
Degenerative, traumatic, and inflammatory diseases
What are primary optic nerve diseases?
Diseases that arise in and principally involve the optic nerve itself
What is the optic nerve primarily composed of?
Axons of retinal ganglion cells
Where do the axons of retinal ganglion cells project from?
Somas in the ganglion cell layer of the inner retina
Where do the optic nerve axons make a sharp turn to exit the eye?
At the optic nerve head
In which part of the optic nerve head are axons from the superior retina located in dogs?
Superior half
In which part of the optic nerve head are axons from the inferior retina located in dogs?
Inferior half
Where are axons from the nasal retina located in the optic nerve head of dogs?
Nasal quadrant
Where are axons from the temporal retina located in the optic nerve head of dogs?
Temporal quadrant
Where can further information about the anatomy and physiology of the optic nerve be found?
In Chapters 2 and 4, in Volume 1 of this text
Which region subdivides the ONH into prelaminar, laminar and retrolaminar regions?
Laminar region
What is the approximate thickness of the canine central laminar?
500 μm
Which collagen types are primarily present in the extracellular matrix (ECM) of the LC in young dogs?
Collagen types I, III, and VI
What is the analogy used to describe the attachment of the LC to the surrounding sclera?
A trampoline
Which cells reside in the optic nerve and can be impacted by the complex stresses and strains in glaucoma?
All of the above
What are the changes in the human LC associated with aging and disease?
Loss of resiliency, compliance, and elasticity
What genetic mutation can cause open angle glaucoma in dogs?
ADAMTS10 mutation
What are the factors responsible for interindividual ONH connective tissue variability?
Both anatomical and microarchitectural factors
What is the purpose of the laminar insertion zone in the ONH?
To anchor the LC to the sclera
What impact do age-related changes in the posterior sclera have on glaucoma susceptibility in dogs?
Increase susceptibility to glaucoma
Which artery supplies the primary blood flow to the eye in dogs?
The external ophthalmic artery
What is the translaminar pressure gradient (TLPG) in dogs?
3.1 Å} 0.3 mmHg/100 μm tissue
What influences the translaminar pressure gradient (TLPG) in the optic nerve?
IOP and RLTP
What is the primary determinant of the translaminar pressure gradient (TLPG)?
IOP
Which species has the highest percentage of optic nerve axons crossing the midline at the optic chiasm?
Dogs
What is the approximate length of a human retinal ganglion cell (RGC) axon?
1 mile
Which segment of the optic nerve is surrounded by the origins of the superior, medial, and inferior recti muscles?
Intracanalicular optic nerve
Which region of the optic nerve head has the greatest concentration of mitochondria, astrocyte processes, and capillaries?
Laminar region
Which part of the optic nerve is visualized on ophthalmoscopy?
The optic disc
Where do the majority of canine RGC axons ultimately project to?
The lateral geniculate nucleus
Where do the axons from the temporal retina remain uncrossed and project to?
The ipsilateral LGN and visual cortex
What is the vulnerability of the optic nerve attributed to?
All of the above
Which type of collagen is primarily found in the extracellular matrix (ECM) of the canine LC?
Collagen type I
What is the approximate range of pore diameters in the canine LC?
12 to 50 μm
What is the primary role of the laminar insertion zone in the ONH?
To anchor the LC to the surrounding sclera
What are the anatomical factors that contribute to interindividual ONH connective tissue variability?
All of the above
Which type of cells are responsible for myelination of optic nerve axons?
Oligodendrocytes
What is the primary cellular component in the retrobulbar, intraorbital optic nerve posterior to the lamina cribrosa (LC)?
Oligodendrocytes
What is the function of the nodes of Ranvier in the optic nerve?
Saltatory conduction of optic nerve impulses
What is the approximate diameter of the canine intraorbital optic nerve?
1825.8 Å} 59.7 μm
Which of the following is true about the optic nerve in dogs?
The optic nerve is primarily composed of retinal ganglion cells
Where do the axons of retinal ganglion cells make a sharp turn to exit the eye?
At the optic nerve head
How are the axons from the superior retina located in the optic nerve head of dogs?
In the superior half of the optic nerve head
What is the relationship between optic nerve diseases and pathology elsewhere in the eye?
Optic nerve diseases can be either primary or secondary to pathology elsewhere in the eye
Which structure is in close proximity to the optic chiasm in dogs?
Third ventricle
What clinical signs can be associated with neuropathology and systemic diseases affecting the region of the optic chiasm in dogs?
Ocular, neurological, and systemic signs
Where is the optic chiasm located in relation to the rostral level of the diencephalon in dogs?
At the same level
What can explain the spectrum of clinical signs associated with neuropathology and systemic diseases affecting the optic chiasm in dogs?
All of the above
Where can additional information about the clinical signs associated with neuropathology and systemic diseases affecting the optic chiasm in dogs be found?
All of the above
What is the anatomical location of the optic chiasm in dogs?
Rostroventral surface of the brain stem
Test your knowledge on optic nerve diseases in dogs, including degenerative, traumatic, and inflammatory conditions. Learn about primary and secondary effects, as well as the involvement of the optic nerve in other diseases.
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