Visual system Flashcards
Anatomy of optic pathway:
Eye - optic nerve - optic chiasm - optic tract - lateral geniculate nucleus - optic radiation - primary visual cortex (V1)
V1 is located in
Occipital love
Where is the lateral geniculate nucleus?
Thalamus
What information goes to the left hemisphere?
Right visual field from right and left eye
What information goes to right hemisphere?
Left visual information from right and left eye
eye can be divided into which regions in terms of visual field?
Temporal retina and nasal retina
Nasal retina information
Decussates in optic chiasm
Temporal retina information
Remains ipsilateral in optic chiasm/ doesn’t cross
Lesion in optic nerve leads to:
Monocular blindness in eye of nerve (loss of peripheral vision - keep the part (nasal) which is covered by both eyes)
Lesion at optic chiasm:
Bi-temporal hemionopsia (tunnel vision)
What leads to tunnel vision?
Losing the temporal fields (carried by nasal fibers)
Another name for tunnel vision =
Bi-temporal hemionopsia
Lesion in optic tract =
Homonymous hemionopsia on same side
Ex of lesion in optic radiation
Meyer’s loop
Meyer’s loop supplies
Upper visual field
Lesion in fiber of optic radiation =
Quadranopsia
Lesion in occipital lobe =
Contralateral homonymous hemianopsia with macular sparing
Why is there macular sparing in occipital lobe lesion?
Dual blood supply
3 main layers of eye:
- Fibrous
- Vascular/uvea
- Neural
Fibrous layer =
Sclera
Cornea
Where do muscles attach?
Sclera
Uvea =
Choroid
Ciliary body
Iris
Choroid =
layer of connective tissue and blood vessels. nourish outer layers of retina
Ciliary body consists of =
Ciliary muscles
Ciliary processes
Zonules
Function of ciliary body =
Control shape of lens
Formation of aqueous humor
Iris lies between the
Lens and cornea
Neural layer =
Retina
Center of retina in marked by the
Macula and fovea
Fovea =
High concentration of photo receptors. Visual acuity
Purpose of eye movements:
To move or maintain visual target on fovea (with highest res vision)
Eye movements can be:
Conjugate
Disconjugate
Purpose of eye movements can be:
Gaze stablising
Gaze shifting
Conjugate eye movements:
Vestibulo-ocular
Optokinetic
Saccade
Smooth pursit
Vestibulo-ocular:
Gaze stabalisation
Rapid/breif head movement
Optokinetic:
Gaze stabalisation
Slow head movements
Saccade:
Gaze shifting
Directs eyes towards visual target
Smooth pursuit:
Gaze shifting
Follows moving visual target
Disconjugate eye movement and purpose:
Vergence
Adjusts eyes for different viewing distance
Extraocular muscles:
- Lateral rectus
- Medial rectus
- Superior rectus
- Inferior rectus
- Superior oblique
- Inferior oblique
SO4 LR6
Superior oblique 4
Lateral rectus 6
Elevation by
Superior rectus
Inferior oblique
Depression by
Inferior rectus
Superior oblique
Intorsion by
Superior rectus
Superior oblique