Optometric Terms 2 Flashcards
dynamic retinoscopy
retinoscopy performed while the patient fixates at near
term dynamic is used bc the patient’s accommodation is active
dynamic retinoscopy is in contrast to
static retinoscopy, which is done while the patient fixates at distance, where theoretically accommodation is relaxed
eccentric fixation
in amblyopia, the condition in which under monocular viewing the amblyopic eye uses a point other than the fovea for straight-ahead viewing
elevation
aiming the eyes upward
emmetropia
the condition under which an individual does not measure any refractive “error”
the patient sees well at distance without compensatory lenses, and sees blur when plus lenses are applied
enucleation
the surgical removal of the entire eye
esotropia
in strabismus, the condition in which one eye deviates inward while the other eye fixates
excycloversion
rotation of the eye around the anterior/posterior axis toward the temple
exotropia
in strabismus, the condition in which one eye deviates outward while the other eye fixates
extorsion
rotation temporalward
extra-ocular muscles
6 striated muscles that attach to the outside of each eye (total 12) and which allow the eye to move. these muscles coordinate together to produce eye movements in the different positions of gaze
lateral rectus, medial rectus, superior rectus, inferior rectus, inferior oblique, superior oblique
lateral rectus (LR)
abduction (away from the nose)
innervated by cranial nerve VI (the abducens)
medial rectus (MR)
adduction (towards the nose)
innervated by cranial nerve III (oculo-motor)
superior rectus (SR)
adduction, elevation, and intorsion
innervated by cranial nerve III
inferior rectus (IR)
adduction, depression, and extorsion
innervated by cranial nerve III
inferior oblique (IO)
abduction, elevation, and extorsion
innervated by cranial nerve III
superior oblique (SO)
abduction, depression, and intorsion
innervated by cranial nerve IV (trochlear)
farpoint
the point upon which the visual axis of the eye is sharply imaged on the retina when accommodation is relaxed
the far point of a “normal” eye is said to be at
optical infinity
fixation
the process, condition, or act of directing the eye toward an object of regard, causing the image of the object to be aligned on the fovea
in what sense is fixation an active process
during fixation there are small involuntary saccades, which are imperceptible to the naked eye
the oculomotor system sends and receives info to the brain in order to keep the image centered on the fovea, where it will best be seen
fixation disparity
exists when there is a small misalignment of the eyes when viewing an object binocularly
since the corresponding points still fall within Panum’s areas, the object is still seen as single
the misalignment may be vertical, horizontal, or both
the misalignment in fixation disparity is measure in what?
how does it compare to misalignment in strabismus?
measured in minutes of arc
much smaller than that of a strabismus, although it may reduce a patient’s comfort and level of stereopsis
a patient may/may not have fixation disparity and a patient may have a different fixation disparity at distance than near
flipper
a lens carrier designed to hold two pairs of lenses such as plus lenses on one side and minus on the other, or base-in prisms on one side and base-out prisms on the other
fovea centralis
a tiny spot in the center of the macular area of the eye which enjoys a high concentration of cones
visual acuity is said to be the sharpest at
the macula
the eyes move to position the images of objects of regard on …
on the fovea, as that is where they will be seen most clearly
frontal lobe
sometimes referred to as the “executive” part of the brain
functions of the frontal lobe (4)
involve the ability to recognize future consequences resulting from current actions
choose between good and bad actions (or better and best)
override and suppress unacceptable social responses
determine similarities and differences between things or events
the frontal lobes also play an important part in
retaining longer term memories which are not task-based (often associated with emotions derived from input from the brain’s limbic system)
the frontal lobe modifies those emotions to generally fit socially acceptable norms
fusion and its 2 components
the unification of the individual images from each eye into a unified percept
sensory and motor
sensory fusion
single, unified percept that results when corresponding retinal areas are stimulated by images of the same object or images of compatible content
the ability to appreciate two similar or compatible images, one with each eye and interpret them as one
for sensory fusion to occur, the images must be
located on corresponding retinal areas and also sufficiently similar in size, brightness, and sharpness
unequal images present a severe obstacle to fusion
motor fusion
the physical movement of the eye to achieve a single image when presented with different retinal images to result in/ maintain sensory fusion
the ability to align the eyes in such a manner that sensory fusion can be maintained
the stimulus for fusional eye movements is
retinal disparity outside of Panum’s area and the eyes moving in opposite directions (mergence)
sensori-motor fusion refers to the
quality and quantity of the binocular response
grades of fusion
worth divided binocular vision into grades, relative to the type of demand presented by a target
first degree fusion
(superimposition) refers to the common localization of dissimilar but compatible images presented separately to each eye
ex: fish and bowl targets from mirror stereoscope (one eye sees fish other sees bowl, when fusion occurs, patient will see a fish in a bowl)
second degree fusion
(flat fusion) refers to the single simultaneous perception of identical targets, one presented to each eye
upon examination of a second degree fusion target, the distance between all corresponding (homologous) points will be found to be the same
ex: AN 1 card used in the Brewster stereoscope
most second degree fusion targets include
a first degree fusion component that acts as a suppression control
“fusion lock”
enhancing or guiding binocular posture and providing a “framework” for the simultaneous perception of the first degree fusion components
third degree fusion
stereopsis, refers to the perception of depth when viewing targets that are designed with retinal disparity
stereopsis
binocular appreciation of depth due to retinal disparity
upon examination of a third degree fusion target
the distance between corresponding (homologous) points will vary, resulting in perception of depth when fusion occurs
although the distance between corresponding points varies, the differences are not great enough to prevent the entire target from being seen as single
an example of third degree fusion target might be
clown vectogram
when the 2 films are super imposed the objects do not coincide exactly; this disparity is what vies rise to the perception of 3D when the appropriate fusion response is made
hemianopsia
literally “half vision” a condition resulting from malfunction or damage to one side of the optic tract
common causes of hemianopsia
stroke, trauma, and tumor
hemianopsia can vary from
absolute loss of all vision on one side (light, form, and color) to a relative loss where vision is reduced, but not completely missing
relative heminaopsias may vary from light or motion detection only in the impaired field to subtle decreases sensitivity only demonstrate on careful visual field testing
the location of damage or lesion along the visual pathway determines the type of field loss
binasal hemianopsia
vision is missing in the inner half of both the right and left visual fields
bitemporal hemianopsia
vision is missing in the outer half of both right and left visual fields
homonymous hemianopsia
loss of vision in the same visual field of both eyes
Hering-Bielschowsky after image test
diagnostic test used to determine the status of correspondence between the eyes
Hering’s Law of Equal Innervation
coordinated binocular eye movements require symmetrical innervation of the muscles of each eye
versional movement
normally our eyes move together in the same direction, called versional movement
Hering’s Law states that
yoke muscles receive equal innervation
for example when looking to the left:
the left lateral rectus and right medial rectus muscles simultaneously contract
and the left medial rectus and right lateral rectus muscles relax
differentiate the two sets of yoke muscles
left lateral and right medial rectus muscles are yoke AGONIST (contracting) muscles
left medial and right lateral rectus muscles are yoke ANTAGONIST (extensor and flexor) muscles
hippocampus
brain structure located inside the medial temporal lobe of the cerebral cortex
belongs to the limbic system and plays a major role in short term memory and spatial navigation
in Alzheimer’s disease, the hippocampus is
one of the first regions of the brain to suffer damage,
memory problems and disorientation appear among the first symptoms
damage to the hippocampus can also result from
oxygen starvation (anoxia), encephalitis, or medial temporal lobe epilepsy
people with extensive hippocampal damage may experience
amnesia, inability to form or retain new memories
Hirschberg test
screening test that can be used to detect the presence of strabismus
performed by shining a penlight in the person’s eyes and observing where the light reflects off the corneas
in Hirschberg test, with normal ocular alignment the light lands on the center of both corneas
but in exo, eso, hyper, hypo…
exotropia the light lands on the medial aspect of the cornea
esotropia the light lands on the lateral aspect of the cornea
hypertrophic the light lands on the inferior aspect of the cornea
hypotonia the light lands on superior aspect of the cornea
horopter
horizon of vision
the sum total of points in space which can be seen as single by the two eyes
defined as the locus of all points that are imaged on corresponding retinal elements at a given fixation distance
a line can be drawn through the object of regard such that all the points on the line are imaged on the corresponding retinal elements and are seen singly. all the points not lying on the horopter are…
imaged by disparate retinal elements and are seen as double (diplopia elicited by object points off the horopter is called “physiological diplopia”
hyperopia
also called farsightedness, the condition in which in the uncorrected eye, sight rays come to point focus behind the retina
hyperopia is compensated for by the use of
plus lenses
hyperphoria
the tendency of one eye to aim higher than the other
hypertropia
in strabismus, the condition in which one eye deviates or aims upward, while the other eye fixates
hypophoria
the tendency of one eye to aim lower than the other
hypotropia
in strabismus, the condition in which one eye deviates or aims downward, while the other eye fixates
incycloduction
the rotation of the eye around the anterior/posterior axis toward the nose
intermittent
not constant
in strabismus the deviation is manifested irregularly, i.e. it is not always present (there are times and conditions when the eyes are aligned)
intorsion
rotation nasalward
iris
the colored tissue surrounding the pupil which is involved in regulating the amount of light that enters the eye
isometropia
the condition in which both eyes have equal or nearly equal refractive status
JND (just noticeable difference)
the smallest amount of change that can be made with the patient being aware of the change
the smaller the JND, the better the patient is at making fine discriminations
Krimsky test
a test of binocular motor alignment by which a penlight is shone at the eyes and the position of the light reflect centered with a prism, thus indicating the amount of deviation
lag of accommodation
when presented either with near targets or with minus lenses placed in front of the eyes, most individuals accommodate less than is needed to bring the target into focus
this under-accommodation is referred to as the lag of accommodation and is quantified by the difference between the actual accommodative stimulus and the measured accommodative response
laterality
the individual’s ability to understand and identify right and left on his/her own body
lateral geniculate nucleus (LGN)
one of the primary processing centers for visual info received from the retina of the eye
the LGN is located inside the thalamus of the brain
where does LGN receive info from
receives info directly from the retinal ganglion cells via the optic nerve and from the reticular activating systems
neurons of the LGN send their axons through the
optic radiations, a direct pathway to the primary visual cortex, also known as the striate cortex, in the occipital lobe
LGN is where the process of … starts?
co-ordinating vision from the 2 eyes
it acts as sort of a “filter” determining what and how much info goes to visual cortex
LGN receives many strong feedback connections from
the primary visual cortex
i.e. info travels in both directions
localization
part of the process that helps the individual to identify the “where is it?” of objects in space
lustre
(luster) refers to the appearance of 2 different colors, usually red and green, that when viewed simultaneously and superimposed, result in a mix of color, which is often unstable, and frequently described as “muddy brown” or “orange” and having a glossy or metallic quality
macula
area in the back of the retina, located temporally and slightly below the optic nerve head
what does the macula contain
fovea centralis
macular integrity tester (MIT)
an instrument that provides feedback of the location in space where the fovea is aiming
useful in testing for and training eccentric fixation
maddox rod
instrument used by the optometrist in measuring the alignment of the eyes
minus
(concave) changes the path of light so that the focus is on the same side of the lens as is the object and closer to the lens than the object
makes objects of regard appear smaller and closer (SI of SILO)
monocular cues to depth
cues that help us determine relative distances of things include:
1) apparent size
2) interposition
3) aerial perspective
4) shading
5) geometric perspective
6) relative velocity
7) motion parallax
monocular cues to depth: apparent size
(small retinal objects are interpreted as distant objects and large as near); objects progressively increase in size as they move towards us (looming)
monocular cues to depth: interposition
relatively nearer objects tend to conceal or overlay more distant objects
monocular cues to depth: aerial perspective
water vapor, dust, and smoke in the atmosphere scatter light and make stint objects indistinct and relatively color desaturated
monocular cues to depth: shading
light falling on solid objects causes shadows to be cast, and on curved surfaces causes a gradation in the intensity of shadow
monocular cues to depth: geometric perspective
physically parallel lines converge toward a vanishing point at the horizon e.g. railroad tracks
monocular cues to depth: relative velocity
image velocity of a moving target in the distance is lower than the image velocity of the same moving target when it is nearby
monocular cues to depth: motion parallax
movement of the head cause the images of near objects to move opposite the head and the images of far objects to move with the head, assuming the fixation point is at an intermediate distance
