Vision Flashcards
in myopia the eye is too long/short
too long
what eye condition is caused by a lens that is too thin or an eye that is too short
hyperopia
people with myopia have difficulty seeing things that are close/far
far
what special type of glasses does astigmatism require
cylindrical glasses that are only curved in one plane
what is amblyopia
a lazy eye
pathology of old age myopia
lens gets stiffer and less able to stretch and thin out to focus on close things
what is diplopia
double vision, usually from nerve palsies
what are the intrinsic eye muscles
ciliaris muscle, constrictor and dilator pupillae
afferent pathway of light on eye
falls on retina –> optic nerve –> III nucleus in midbrain
efferent light reflex
III nucleus in midbrain –> preganglionic parasympathetic fibres of III –> ciliary ganglion in orbit –> postganglionic fibres –> contrictor pupillae
what is Horner’s syndrome
pupils of different sizes (aniscoria)
would a III palsy usually have pupillary reflex
yes they would. Conditions that cause this palsy don’t usually affect parasympathetic fibres. If the reflex is absent then there may be a cerebral artery aneurysm
how do postganglionic sympathetic fibres travel in head and neck
along with blood vessels
what is phototransduction
conversion of light wave energy into an electrochemical response in rods and cones
how do rods and cones activate the optic nerve
by producing an action potential
what part of the rods and cones turns the light into electrochemical response
outer segment of stacked lamellae
visual pigment of outer segments of rods
rhodospin
visual pigment of outer segments of cones
opsins
process of action potential production from light
light energy on pigment –> cis to trans –> bleaches –> cascade of processes –> Na+ channels close –> hyperpolarisation
how do visual pigments regenerate
vitamin A takes it back to cis from trans
signs of vit A deficiency in eye
bitot’s spots on conjunctiva
corneal ulceration
opacification of cornea
visual defect caused by damage to optic chiasm
bitemporal hemianopia
where is the primary visual cortex
occipital lobe area 17
what does the optic tract contain
fibres from the same one half of vision in both eyes (i.e. the left half of the field)
where does the optic tract fibres synapse
in the lateral geniculate body of the thalamus
