Vision and Eye Movement Flashcards
normal spherical-shaped eye
Distant objects are focused on the retina when the ciliary muscles are relaxed
emmetropia
elongated eyeball
The focal plane falls in front of the retina
Only objects which are close to the eye are in focus
Near-sightedness
myopia
flattened eyeball shape
The focal point of the image falls behind the retina
Far-sightedness
hyperopia
If the cornea gradually thins at the center and protrudes, becoming cone-shaped this results in
keratoconus
Keratoconus can
impair vision
caused by autosomal dominant gene
treated with corneal transplants
type of spherical aberration
affects the ability of the eye to focus
cornea has various radii of curvature
astigmatism
decrease of something, decreasing vision with age
not a neural problem
loss of accomodation (near vision)
presbyopia
diabetes untreated/unmanaged can coss progression of many things, microvascular disease (as the arteries get smaller, they can become blocked leading to the sbove)
loss of blood supply and nutrients to the retina causing vision loss
diabetic retinopathy
film/clogging of the eye
opacity (cornea looks milky)
can occur with aging or sped up with genetics
cataract
front chamber is filled with aqueous and too much of this causes excess pressure on the eye, has to be absorbed through canal of schlem and go out to be absorbed and if it doens’t this occurs
pressure builds up and pushes lens back
puff of air at the eye doctor is checking for this
glaucoma
blind spot due to lesion
vascular lesion, deposit of pigment in the retina, etc.
dancing light in the eye
think migraine with light
scotoma
could have damage from injury or genetics and retina falls off of the globe and falls forward in the fluid when it should be firmly attached
think of curtain closing in from the sides after a theater show
can lead to permanent blindness if not treated right away
detached retina
age-related eye disease affecting the small part of the retina responsible for sharp, straight-ahead vision that is needed for driving and reading small print. This disorder usually occurs in people 65 years of age or older.
macular degeneration
what are the extrinsic eye muscles
Superior Rectus (CN III)
Inferior Rectus (CN III)
Sup oblique (CN IV Trochlear)
Inf oblique (CN III)
Lateral rectus (CN VI Abducens)
Medial rectus (CN III)
moves the eye towards the nose
medial rectus
moves the eye away from the nose
lateral rectus
moves the eye up
superior rectus
moves the eye down
inferior rectus
rotates the eye down and away
superior oblique
rotates the eye up and away
inferior obliqu
why do we have conjugate eye movements?
For stable images in the two eyes
To avoid diplopia (double-vision)
Eyes must track a moving object in a coordinated fashion
This is complex since the eyes are in an unstable platform (the moving head)
Visual and vestibular systems are involved
eye tracking, following an object
smooth pursuit
directing the gaze from one target to another (A to B)
saccades
voluntary saccades
intentional
when the door slams and you reflexively look in that direction)
saccades
reflexive
Reflexive movement of the eyes in response to vestibular stimulation
Normally the VOR produces conjugate eye movement in the direction opposite the movement of the head
right turn of the head, the eyes go to the left the same degree as the head turn
vestibularochlear reflex
Rhythmic oscillation of the eyes
Fast in one direction and slow in the other direction (jerk)
nystagmus
What part of the nervous system mediates the slow phase?
What part of the nervous system mediates the fast phase?
railroad nystagmus
eyes track until out of site and then dart back to the middle and repeat and looks just like nystagmus that we would have with a disease
Optokinetic Nystagmus
Indicates underlying pathological or abnormal condition
May be associated with nausea, vertigo, unsteadiness, falling
spontaneous nystagmus
What are some pathologies for spontaneous nystagmus
Lesion to labyrinth, CN VIII (vestibular portions), brainstem, cerebellum
Lesions that result in an imbalance of neural inputs to the CNS
what is paired with the anterior SCC
posterior SCC
what is paired with the posterior SCC
anterior SCC
what is paired with the horizontal SCC
horizontal SCC
How does the body know we are not moving?
our paired system
How does our body know it is moving?
one side is inhibited and one is stimulated
why do I not see spontaneous nystagmus with a PT that comes in? How can we override this?
can have spontaneous nystagmus that you cannot see in a well lit room with some visual stimulus to fixate on so the vision will override the spontaneous nystagmus
when you take this away, the spontaneous nystagmus can show up when they cannot focus on something
CNS integrates vestibular information looking for balanced inputs from
both sides
If there is an imbalance in the neural inputs/firing rates
some accommodation, eye or body movement needs to take place.
when can compensation occur
if the lesion is to a peripheral vestibular organ and the other side is intact.
Sense that the world is spinning or that your head or body is spinning
vertigo
objects/world spinning
objective
self spinning
subjective
Fainting
Partial or complete loss of consciousness
syncope
light headedness
presyncope
what can cause syncope
Temporary with recovery
From reduction in blood flow and O2 to the brain
when we can stop/control the nystagmus
fixation
what allows us to override the feeling of dizzines
fixation
