Anatomy of the orbit and visual pathways Flashcards
What are the 3 layers of the eye?
fibrous outer layer:
- anterior cornea
- posterior sclera
vascular middle layer:
- choroid
- ciliary body and iris
neural inner layer:
- retina
Sclera functions
maintenance of eyeball shape
attachment for extrinsic muscles
What muscles control the iris?
radial - dilator (dilator pupillae) - sympathetic innervation
circular - constrictor (sphincter pupillae) - parasympathetic innervation
What is a scotoma?
blind spot
Cornea function
bends light to form the image on the retina
Lens function
focusses light
refraction
What position is an image on the retina compared to what we see?
image on retina inverted and reversed
Cones function
colour vision
high visual acuity
Rods function
low visual acuity
good contrast - nocturnal vision
Describe the fovea centralis
central part of macula lutea
most acute vision/central/colour vision - high density of cones
lies in the visual axis - fixation point when gazing directly at an object
What is a binocular visual field?
the overlap between each eye’s visual field
Name the components of the visual pathway from the retina backwards
retina (1st and 2nd order neuron cell bodies)
optic nerve
optic chiasm (partial decussation)
optic tract
lateral geniculate nucleus (3rd order neuron cell bodies)
optic radiations
visual cortex
What is the sensory input and motor output of the corneal reflex?
sensory input = touch cornea = trigeminal nerve
motor output = scrunch face = facial nerve
What is an Argyll Robertson pupil?
usually bilateral
small pupils
pupils constrict when focus on nearby objects - accomodation reflex
does not respond to light - direct or consensual reflex
commonly associated with syphilis of CNS and diabetes mellitus
