Vision 2 Flashcards
what are the roles of intrinsic muscles?
control pupil diameter & helps alter lens curvature to enable us to see near objects
what are the roles of extrinsic muscles?
move the eye
what are the 6 extrinsic ocular muscles that move the eye?
Medial rectus (MR) Lateral rectus (LR) Inferior rectus (IR) Superior rectus (SR) Superior Oblique (SO) Inferior Oblique (IO)
what are the actions of MR?
Adduction
what are the actions of LR?
Abduction
what are the actions of SR?
Elevation
Adduction
Intorsion
what are the actions of IR?
Depression
Adduction
Extorsion
what are the actions of SO?
Intorsion
Depression
Abduction
what are the actions of IO?
Extorsion
Elevation
Abduction
what do you look for in right third nerve palsy?
Drooping eyelid
Eye can move only laterally (and slightly down)
what do you look for in left forth nerve palsy?
Eye moving up when adducted
what do you look for in abducent (6th) nerve palsy?
Eye being adducted
Eye not able to abduct
what is Strabismus?
squint-Misalignment of the eyes
what are the 2 different types of squint?
Esotropia (manifest convergent squint)
Exotropia (manifest divergent squint)
what is ambylyopia?
(lazy eye) where brain supresses the image of one eye leading to poor vision in that eye without any pathology (correctable in early years using eye patches to stimulate the “lazy” eye to work)
what is diplopia?
(double vision) – usually occurs in squints occurring as a result of nerve palsies.
what is the definition of the visual field?
Everything you see with one eye (including in the periphery)
where do the medial nasal fibres cross to opposite side?
optic chiasma
the optic tract contains fibres from which part of the eyes?
ALL fibres from the opposite half of the visual field
where do the fibres from the optic tract synapse?
LGB of the thalamus
where is the primary visual cortex?
occipital lobe
What damage do you expect when the optic nerve is damaged?
blindness in one eye
What damage do you expect when Optic chiasma disrupted in the middle?
bitemporal hemianopia- lateral vision of both eyes affected
What damage do you expect when optic tract is damaged?
contralateral homonymous hemianopia-lateral vision in one eye and medial vision of the other is affected
What damage do you expect when optic radiation is damaged?
contralateral homonymous hemianopia-lateral vision in one eye and medial vision of the other is affected
what are the 3 Intrinsic eye muscles?
Ciliaris muscle in ciliary body
Constrictor pupillae in iris at pupillary border
Dilator pupillae radially running muscle in iris
what is the Pupillary reaction to Increased/decreased illumination?
Increased illumination parasympathetic-both pupils constrict
Decreased illumination sympathetic-pupils dilate
what is direct and consensual reflex?
Light shined into eye=direct reflex
The other eye has no light shined at it, but constricts anyway=consensual reflex
what is anisocoria?
Pupils of different sizes eg: Horner’s syndrome, can be caused by trauma
What are some common causes of absent/abnormal pupillary reflex
Diseases of the retina – detachment/ degenerations or dystrophies
Diseases of the optic nerve – such as in optic neuritis (frequently seen in MS)
Diseases of the III cranial nerve (efferent limb)
what is horner’s syndrome?
Anisocoria due to damage to the sympathetic innervation to the pupil.
what are symptoms of horner’s syndrome?
on affected side:
constricted pupil
Drooping of the upper eyelid
Little or no sweating
