optics + nerves Flashcards
emmetropica
no refractive error
ligth focused onto retina
myopia
light focuses in front of retina
distance targets blurred
require negative lens = concave
hypermetropia
light focuses behind retina
near targets blurred
needs positive lens = convex
astigmatism
eye has unequal refractive powers with different focal points
require cylindrical lenses
presbyopia
reduction in ability to accomodate for close-work with age
reading glasses
that the ciliary muscle, as it ages, loses its ability to contract and change its configuration
down and out eye postion
3rd nerve palsy
eye problems in multiple sclerosis
optic neuritis - blind spot, pain on move, impaired colour vision, RAPD
VI palsy - cant abduct eye
what can cause 3rd nerve palsy that has a fixed dilated pupil?
cavernous sinus thrombosis **posterior communicating artery aneurysm (most serious) rised ICP tumour trauma
why does 3rd nerve palsy also cause ptosis ?
CN III also supplies levator palpebrae superioris (responsible for lifting eyelid)
why does 3rd nerve palsy also cause dilated fixed pupil ?
oculomotor contains parasympathetic fibres that innervate sphincter muscle of iris
causes of 3rd nerve palsy where pupil is spared
diabetes
hypertension
ischaemia
presentation 3rd nerve palsy
ptosis - drooping eyelid
dilated non reactive pupil
divergent strabusmus = down + out position
multiple sclerosis
chronic + progressive involving demyelination of myelinated neurones in CNS (inflam process - immune cells against myelin)
more common in women
eye abnormalities usually first presentation
presentation of multiple sclerosis
optic neuritis - blind spot, pain move, impaired colour vision
CN VI palsy - cant abduct
cant sense if leg is flexed or extended
cerebellar ataxia
myotonic dystrophy
usually presents in childhood
genetic disorder - autosomal dominant
delayed muscle relaxation on stopping voluntary action
