Optometric Terms 3 Flashcards
MFBF
monocular fixation in a binocular field: used frequently in amblyopia therapy, it is a created situation where both eyes receive the peripheral info, while the amblyopic eye is presented with a detailed, central task that it alone can perceive
MFBF is used as a “bridge” between
monocular and binocular activities and is used to override the tendency of the “good eye” to exert active cortical inhibition over the amblyopic eye
myopia
“nearsightedness” condition in which in the uncorrected eye, light rays come to point focus in front of the retina
myopia is compensated for by
minus lenses
nasal
towards the nose
NPC
near point convergence: closest point that an object of regard can be moved toward the nose without loss of fusion
neglect
(visual neglect, hemispatial agnosia, visual/spatial neglect, or semi-imperception)
caused by: injury from a stroke or other trauma, neglect is a passive unconscious decreased awareness of part of the field of view or other stimuli to one side of the body
usually occurs with a visual field defect, but may occur in absence of field loss
a person with field loss
would be aware of the area of loss and like to make compensations
a person with visual neglect and field loss
unconsciously neglect the area of the field loss and be less likely to compensate for the defect
damage to the right side of the brain may cause both
visual field loss and visual neglect to the left side
how does right brain injury neglect compare to left?
usually more severe
most common site for visual neglect is
parietal lobe, but damage to frontal lobe and even deeper structures (thalamus and basal ganglia) may cause it
noncomitant
(incomitant) in strabismus the condition in which the angle of deviation is not constant, but varies according to position of gaze
causes for noncomitant
this may be due to paralysis of one or more of the extra-ocular muscles, or from scar tissues after surgery
nystagmus
refers to rapid involuntary movements of the eyes that may be from side to side (Horizontal nystagmus), up and down (vertical nystagmus) or rotary
optic nerve
part of the nervous system that transmits the impulses of sight from the retina along the visual pathways
how many branches of the optic nerve are there
11 currently known
OKN
optokinetic nystagmus: based on the principle that the eyes tend to follow or track the motion of one element at a time in a steadily moving display
as the tracked element moves out of sight, the eyes will “snap back” to fixate and follow another one
OKN in infant
sub cortically-mediated function is present at about five days after birth
can be used as an objective measure of an infant’s ability to see detail in a moving stimulus, such as a bar grating or OKN drum
the absence of an OKN response suggests that the infant may not perceive the elements of the moving target as separate
organic
caused by a pathological or anatomical problem
orthophoria
condition in which the position of the eyes is not changed when binocularity is broken or interrupted as during an alternate cover test
the doctor will see no movement upon removing the occluder
paired cranial nerves
12 pairs of nerves emanate from the nervous tissue of the brain
ultimately exit/enter the cranium through openings in the skull
motor components of the cranial nerves are derived from what? and control what (3 examples)
cells located in the brain that send axons out of the cranium where they ultimately control:
1) muscle (e.g. eye movements)
2) glandular tissue (e.g. salivary glands)
3) specialized muscle (e.g., heart or stomach)
sensory components of cranial nerves originate from
collections of cells that are located outside the brain; these collections of nerve cells bodies are called sensory ganglia
cranial nerve I
olfactory
smell
cranial nerve II
optic
vision
cranial nerve III
oculomotor
eye movement and pupil dilation
cranial nerve IV
trochlear
innervates superior oblique, turns eye down and in
cranial nerve V
trigeminal
chewing
somatosensory info from the face & mouth
touch and pain
cranial nerve VI
abducens
moves eyes temporally
cranial nerve VII
facial
controls most facial expressions
secretion of tears & saliva
taste, somatosensory info from ear
cranial nerve VIII
vestibulocochlear (auditory)
hearing
equilibrium and balance
cranial nerve IX
glossopharyngeal
taste (posterior 1/3 of tongue)
somatosensory info from tongue, tonsils, pharynx;
controls some muscles used in swallowing
cranial nerve X
vagus
sensory motor, and autonomic functions of viscera (glands, digestion, heart)
cranial nerve XI
spinal accessory
controls trapezius & sternocleidomastoid
controls swallowing movements
controls muscles used in head movement
cranial nerve XII
hypoglossal
controls tongue movements
palpebral fissure
the area of the eye seen when the lids are open
Panum’s areas
in reality correspondence between the 2 eyes does not occur rigidly, point by point
to each retinal point there is a small elliptic-shaped zone in which an image may fall and still give rise to a common visual direction when stimulated simultaneously with a specific retinal point in the other eye
these zones are called Panama’s areas
Panum’s areas are smaller where?
at the fovea
increasing in size in peripheral retina
this helps to explain why a strabismic may experience gross peripheral fusion even though the eye is deviated
the increase in the spatial extent of panum’s area in the peripheral visual field serves three useful purposes:
1) increasing the SIZE of Panum’s area: matches the increasing coarseness of peripheral vision; receptive field size increases and the visual acuity decreases as a function of eccentricity
2) increasing the THICKNESS of Panum’s area prevents peripheral diplopia when fixating flat targets held at close range
3) increasing the EXTENT of Panum’s area peripherally makes cyclofusion possible despite cyclovergence errors of as much as 2 degrees between the two eyes
panum’s area expands and contracts depending on
the size, sharpness, and speed of the stimuli
parallax
apparent displacement of an observed object due to a change in the position of the observer
in the real world, parallax is an important cue to
depth, and using parallax one can determine the relative distance of objects
what can be used to produce a parallax-like effect in the therapy room (and what is this called?)
paradoxical parallax evaluates the patient’s ability to respond appropriately to visual info
can be produced using prisms and filters
paralysis
the complete loss of muscle function of one or more muscle groups
often includes loss of feeling in the affected area
paramacular
referring to the area immediately adjacent to and surrounding the macula
paresis
a condition typified by partial loss of movement, or impaired movement
in the optometric sense it is usually used to describe the muscles of the eyes
parietal lobe
involved in the visual process
deals with:
1) somatosensory info (kinesthesis and body awareness)
2) cognition & info processing
3) pain and touch sensation
4) spatial orientation
5) speech
6) visual perception
7) timing
8) movement
integrates sensory info from different modalities, particularly determining spatial sense and navigation
currently believed that the majority of the Magnocellular fibers travel to the parietal lobe via
the dorsal stream
parasympathetic nervous system
a part of the autonomic nervous system
returns the body function to normal after they have been altered by sympathetic stimulation
1) slowing of heart beat
2) lowering of blood pressure
3) constriction of the pupils
4) increased blood flow to the skin and viscera
5) resumption of peristalsis in the GI tract
in times of danger… (what happens in the and)
the sympathetic system prepares the body for violent activity
when the danger is over
the parasympathetic system reverses these changes induced by the sympathetic system
P.D.
inter-pupillary distance, refers to the distance, expressed in millimeters, between the pupils of the patient’s eyes
perimeter
an instrument used to evaluate the central and peripheral fields of vision
periodicity
in strabismus, referring to the distances at which the deviation is manifest
phoria
the natural “resting position” of the eyes when they are not viewing the same object at the same time
represents a “mismatch” between where objects really are and where the person judges them to be
photophobia
excessive sensitivity to light, which may include aversion to sunlight and well-lit places
plegia
paralysis in which all movement is lost
pointzero
in strabismus, this is Jampolsky’s term to define the point on the retina of the deviating eye which receives the image of the object fixated by the fovea of the non-strabismic eye when no vergence demand is present
polaroid filters
allow full transmission of light in one direction, gradually reducing the amount of transmission to “zero” at a point 90 degrees away
by using a pair of polaroid glasses with 2 filters oriented in opposite directions from each other and a special set of polaroid targets we can control the info that is available to each eye
targets using polaroid are usually designed to provide a stereoscopic 3-D effect by using 2 similar images which are slightly offset from each other
post traumatic vision syndrome (PTVS)
following a TBI a patient may develop a constellation of symptoms that may include, but are not limited to:
blurry vision, diplopia, headaches, spatial disorientation, photophobia, visual hallucinations, poor attention and concentration, and poor visual memory
conditions often associated with PTVS include
convergence insufficiency, accommodative dysfunction, exotropia or exophoria, low blink rate, and poor ocular motility
primary visual direction (PVD)
the “straight ahead” oculo-centric location normally determined by the fovea of the non-deviated eye, and from which all other spatial determinations are made
a foveally fixated point is interpreted by the individual as being straight ahead, and the other objects in the visual field are experienced as being located above, below, to the side of, etc. the foveally fixated point
thus, each retinal element has its own subjective visual direction
oculo-centric vs egocentric
could-centric is associated with the fovea (determined by non-deviated eye)
ego-centric- visual direction with respect to the head
if fixation movements are made while the head remains still does oculo-centric or ego-centric direction change?
oculo-centric direction for each fovea does not change, but ego-centric direction does
prism
a wedge shaped lens that changes the direction of light passing through it, but does not change focus
light entering a prism is deviated toward the base (the thickest portion) and the image of the object being viewed appears to move in the direction of the apex (the point)
yoked prism
refers to application of prism when the bases of both prisms are oriented in the same direction
prism can be used in a compensatory way
helping to achieve alignment of the eyes when it is not possible by other means
in the therapy room prisms are also used therapeutically on both a monocular and binocular basis to
create a mismatch between the objects in the real world, and where the prisms (because of the way they displace light) cause the visual system to perceive them to be
as the patient resolves these mismatches he/she learns to use vision in a new, more efficient way
on a binocular basis, prisms
change the demand for convergence in order to keep a target single, and reflexly change accommodation
yoked prisms are used in vision therapy to
help disrupt the normal association between the vestibular and visual systems and create greater demands for re-orientation in space to compensate for the shift of gravity, postural changes, and sense of orientation imposed by the prisms
when the bases of the prisms are facing the same direction over each eye
the space observed is displaced towards the direction of the apex
when the space observed is displaced to the direction of the apex, this disruption of reality causes the patient to
readjust or shift his/her center of gravity to account for the change in position of the space
in addition to the apparent shift in space, yoked prisms in BU or BD can
create the illusion of an increase or decrease of the volume of space
(a room will appear to be longer or shorter than it really is when seen through these yoked prisms)
because the visual system is so dominant compared to other systems in the body,
the patient will often change gait, head or general body posture, or recalibrate perceived spatial relationships to appropriately match the demands of the “new” reality
Yoked prisms can also play a vital role in therapy for an ABI patient
if a patient constantly perceives the world being shifted to the right, yoked prisms may help “realign” that space for that individual, thus re-establishing a sense of stability and orientation
other applications of yoked prism include patients with
autism, attentional difficulties, cerebral palsy, etc
special types of prism called (Peli prisms) can
also be incorporated into spectacle lenses and used as an alerting mechanism for patients with visual field defects
proprioception
distinct sensory modality that provides feedback solely on the status of the body internally
sense that indicates whether the body is moving with required effort, as well as the relative position of parts of the body, and where they are located in relation to each other
pupillary responses
observed responses of the pupils in response to certain stimuli (3 which affect both eyes, even if only one eye is stimulate)
direct, consensual, accommodative
direct pupillary response
the pupil of the eye constricts (gets smaller) when a light is shone into that eye
consensual pupillary response
the pupil of the fellow eye also constricts when a light is shone into an eye
accommodative pupillary response
the pupils constrict in response to the stimulation of accommodation
pursuit
the type of eye movement used when following a moving target, to keep the image of the object of regard on the fovea
believed to be mediated in the occipital lobe
relatively slow eye movements (compared to the relative speed of saccades) that involve smoothly tracking a moving target while maintaining an accurate fixation
the primary stimulus to initiate a pursuit is the
speed of the object
pursuits are often called a “ “ and allow the individual to
holding movement because it allows the patient to hold or maintain the desired target on the fovea
allow the individual to extract info from a dynamic and changing environment
what ability must one possess before being an efficient pursuit can be achieved
before an efficient pursuit can be achieved one must possess the ability to
make and hold a fixation
how do pursuits and saccades differ
patient has ability to alter the speed or duration of a pursuit during tis progression, whereas that is not possible in a saccade
accurate maintenance of fixation on the moving object is accomplished by a combo of smooth pursuits. and saccades
when the object is moving faster than the pursuit system can keep pace, the faster saccades system is activated to reduce retinal slip and reposition the object of regard on the fovea
even though the image is moving, our sensory system adjusts so that we maintain the sense of straight-ahead and the visual perception of the world remains continuous and stable
