Optometric Terms Flashcards
“A pattern”
a horizontal deviation may be different in upgaze versus downgaze
an “A pattern” deviation shows more eso in upgaze
abduction
movement of the eyes away from the nose
accommodation
the act of focusing the eyes to provide an image clear enough for interpretation
the stimulus to accommodation may come from blur on the retina, or perceived awareness of the proximity of a target
when looking at near objects, accommodation is said to be
“stimulated”
when looking at far objects, accommodation is said to be
“relaxed”
Accommodation is part of the what system?
“idenitifcation system” it tells us the “what is it?” of what we are looking at
accommodative amplitude
the range of distance or lens power over which the patient can stimulate focus to maintain clarity
accommodative insufficiency
a patient who shows a reduced accommodative amplitude
accommodative flexibility
ease with which accommodation can be changed from one distance to another
accommodative infacility
a patient who has reduced accommodative flexibility
accommodative spasm
difficulty releasing (relaxing) accommodation
acquired brain injury (ABI)
- refers to damage to the brain acquired after birth
- It usually affects cognitive, physical, emotional, social or independent functioning
- It can result from TBI (i.e. accidents, falls, assaults, etc.) and nontraumatic brain injury (i.e. cerebral palsy, stroke, brain tumors, infection, poisoning, hypoxia, ischemia, or substance abuse)
visual acuity (VA)
- clearness or sharpness of sight
- the ability to resolve or discriminate contours and to tell when there is a separation of the contour from its background
In the US, visual acuity is usually represented as
A fraction which identifies the size of the smallest letters resolved at the testing distance used
numerator: testing distance used (typically 20’)
denominator: size of the letter read
adduction
movement of the eyes toward the nose
afterimage
a visual sensation that persists after the original light stimulation has ceased
alternating
switching from one eye to the other (in relation to strabismus, it means that either eye may fixate while the other eye deviates)
amblyopia
visual condition in which there is a low or reduced central visual acuity that cannot be “corrected” by traditional refractive means (eg. glasses or contact lenses)
and which is not attributable to disease, injury, or pathology
Amblyopia is said to exist when
there is a set level of acuity, typically 20/40 or worse
or when a difference of 2 or more Snellen acuity lines between the eyes is present
Behaviorally, amblypoia is looked upon as
a dysfunction that hinders a patient’s ability to gather, process, analyze, and respond to visual information in a meaningul way
functional ambloypia
(amblyopia ex anopsia) usually one or more of the following conditions is present before the age of 6:
- significant anisometropia
- constant unilateral esotropia or exotropia
- significant isometropia
- significant unilateral or bilateral astigmatism
- image degradation
Binocular competition in an amblyopic patient causes
adaptations to be made via neural suppression, leading to reduced VA and dysfunctions in the amblyopic eye in such skills as:
- ocular motility
- fixation
- accommodation
- spatial sense
- speed of perception
Vision therapy has a high rate of success for patients with functional amblyopia by improving:
visual acuity and developing abilities in the visual functional areas that are commonly affected by this condition
- ocular motility
- fixation
- accommodation
- spatial sense
- speed of perception
anaglyph
used to provide a stereoscopic 3D effect, when viewed with special anaglyph glasses (each lens a different color, usually red and green or red and blue)
Images are made up of 2 color layers, superimposed, but offset with respect to each other to produce a depth effect. The picture contains two differently filtered colored images, one for each eye. When viewed through anaglyph glasses they produce a unified stereoscopic image
Analytical examination
a comprehensive optometric exam that probes the functioning of the visual system under varying conditions.
The findings from this eval help the dr. understand how vision might be helping or interfering in the patient’s performance, comfort, etc
Angle Kappa
the angle between the pupillary axis and the visual axis
it is termed “positive” when the pupillary axis is nasal to the visual axis and “negative” when the pupillary axis is temporal to the visual axis
what is a normal angle kappa
a positive angle kappa (displacement toward the nose) of up to 5 degrees is normal
aniseikonia
a condition in which the image of an object seen by one eye is different in size and shape from the image seen by the other eye
anisometropia
the condition in which unequal refractive states exist between the eyes
anomalous correspondence (AC)
in strabismus, the condition in which an area other than the fovea of the strabismic eye is “matched” with, or “corresponds” to the fovea of the other eye as far as determining location and direction. This provides the patient with some degree of “depth perception,” and avoids double vision and visual confusion
anterior chamber
the space between the iris and the cornea
antimetropia
the condition where one eye measures hyperopia, and the other eye, myopia
aphasia
loss of the ability to produce and/or comprehend language, due to injury to brain areas specialized for these functions
(Broca’s area, which governs language production
Wernicke’s area, which governs the interpretation of language)
Broca’s area
which governs language production
Wernicke’s area
which governs the interpretation of language
aphasia is not a result of
deficits in sensory, intellectual, or psychiatric functioning, nor due to muscle weakness or a cognitive disorder
apraxia
neurological disorder characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements.
it is a disorder of motor planning which may be acquired or developmental
aqueous humor
what is it, what produces it, what does it do
the thin, watery fluid that fills the space between the cornea and the iris (anterior chamber)
It is continually produced by the ciliary body, the part of the eye that lies just behind the iris.
This fluid nourishes the cornea and the lens and gives the front of the eye its form and shape
asthenopia
a constellation of symptoms relating to visual discomfort, usually at near, such as blurry vision, watery eyes, itchy eyes, etc
astigmatism
the refractive condition in which the light rays from an object are not brought to a single point focus at the back of the eye
astigmatism is compensated for by the use of
lenses with cylinder
ataxia
a neurological sign and symptom consisting of gross lack of coordination of muscle movements
a non-specific clinical manifestation implying dysfunction of parts of the nervous system that coordinate movement, such as the cerebellum, the vestibular system, the thalamus, and parietal lobe
autonomic nervous system (ANS)
the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body
how can the ANS be divided
by subsystems into the parasympathetic (homeostasis/ rest and digest) nervous system and sympathetic (fight or flight) nervous system
it can also be divided functionally, into its sensory and motor systems
Name 8 activities the ANS affects that are generally performed without conscious control
heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal
bagolini lenses
a pair of finely straited lenses that can be used in diagnosing the status of correspondence
bifocal
a lens which contains two different powers for focusing at different distance
typically, the bottom part of the lens is for looking at near distances (13-16”) and the top is for further away
binocular
also, referred to as “fusion”
the simultaneous perception of info from the right eye and the left, organized into a single percept
where does binocularity occur
the brain, not at the retina
4 advantages of binocular vision are
single vision, stereopsis, enlargement of the field of vision, and compensation for the physiological blind spot
normal binocular vision requires what 3 things
1) reasonably clear vision in both eyes
2) the ability of the retino-cortical elements to function in association with each other to promote the fusion of 2 slightly dissimilar images i.e. sensory fusion
3) the precise co-ordination of the 2 eyes for all directions of gaze, so that corresponding retino-cortical elements are placed in a position to deal with two images i.e. motor fusion
binocular summation
also called neural summation
when some cells in the visual cortex receive input from both eyes simultaneously, they show binocular facilitation, a greater level of activity than the sum of the 2 activities evoked separately from each eye (1+1=3)
biocular
the simultaneous perception of info from the right eye and the left eye
(physiological) blind spot
the place in the back of the eye where the optic nerve leaves to carry info along the visual pathways
bc there are no retinal receptors (rods or cones) in this area, and the nerve is myelinated, rays of light that fall on this part of the retina are not “seen” or transmitted along the optic nerve
during the eye health evaluation, the optometrist probes the size and location of this blind spot, to see if it is normal, and…
whether there are any “blind” spots (scotomas) in places where there should not be any (“pathological”)
blindsight
a condition in which the individual responds to visual stimuli without consciously perceiving them
where does the retina send its major neural output
(after a relay at the LGN in the thalamus) to the visual cortex (striate cortex)
this is called the geniculostriate visual pathway
when the striate cortex is removed or damaged, patients can still carry out certain visual discriminations although the level of capacity may change. how is this so?
bc there is another visual pathway (tectopulvinar pathway) that goes directly from the retina to the superior colliculus, pulvinar, and parietal lobe without going to the visual cortex
and these structures may remain intact even when the striate cortex is damaged or removed
blur point
the point at which an object of regard becomes blurred with the introduction of increasing prism or lens power, or by varying the target’s distance
measured either monocularly or binocularly
when the blur point is measured binocularly it represents
the point at which the individual maintains a target single by calling upon changes in accommodation
break point
during binocular fixation, the point at which diplopia (double vision) occurs with gradually increasing prism or lens power, or by varying the target’s distance
Brückner test
a diagnostic test performed using the direct ophthalmoscope
uses the light reflex from the retinal tissue in the back of the eye to assess visual ability
it may help diagnose asymmetric refractive error, fundus lesions, cataract, and strabismus
cataract
the condition in which the crystalline lens loses its transparency and obstructs the passage of light. may be due to the normal aging process or as a result of trauma, etc.
centering
the selection by the individual of an area of space to direct attention and derive meaning
it is part of the system that tells us the “where is it?” of objects of regard
central nervous system (CNS)
consists of the brain and spinal cord, which serve as the main “processing center” for this entire nervous system, and control all the workings of the body
What is the CNS responsible for
receiving and interpreting signals from the peripheral nervous system and also sending out signals to it, either consciously or unconsciously
central visual field
the portion of the visual field, directly straight ahead of the eyes, in which we can see clearly and observe detail
central visual field is in contrast to
the peripheral field, sometimes called “side vision” over which we have awareness but see less distinctly
cerebellum
a region of the brain that plays an important role in the integration of sensory perception, coordination, and motor control
in order to coordinate motor control, there are many neural pathways linking the cerebellum with
the cerebral motor cortex (which sends info to the muscles causing them to move)
and the spinocerebellar tract (which provides proprioceptive feedback on the position of the body in space)
the cerebellum integrates these pathways, like a train conductor, using the constant feedback on body position to fine-tune motor movements
because of the “updating” function of the cerebellum, lesions within it are usually
not so debilitating as to cause paralysis, but rather present as feedback deficits resulting in disorders in fine movement (eg. spasticity), equilibrium, posture, and motor learning
cheiroscope
an instrument that presents a pattern or image to one eye, which is transferred to and projected out of the other eye
cheiroscope is used to test what?
used to probe the presence of first-degree fusion and the stability of binocular posture
2 types of cheiroscopes
wheatstone (which uses sphero-prisms)
mirror stereoscope (which uses mirror images)
ciliary muscle
the smooth muscle fibers in the area behind the iris that aid the crystalline lens in changing its shape for accommodation
comitant
or concomitant, in strabismus, when the angle of deviation is the same in all positions of gaze
concave lens
(minus lens) thinner in the middle and thicker at the edges
minus lenses are used to compensate for
myopia, or nearsightedness
in the vt room, minus lenses are used to
cause changes in accommodation and convergence, and to help develop a better balance between these two systems
concave lenses make objects
smaller and closer (the SI of SILO)
cone
a light-sensitive retinal receptor found in great abundance at the fovea or macular area
responsible for clear central vision, color perception, and bright-light seeing
transform light info into chemical energy so that it can be used by the visual system
confusion
the condition in strabismus where each of the 2 foveas receives an image of a different object
if these images are not suppressed, and correspondence is normal, the patient will perceive the 2 objects as superimposed and in the same location
conjuctiva
mucus membrane covering the anterior surface of the eye and the lining of the lids
constant
in relation to strabismus: one eye is always deviated (turned) while the other fixates
there is never a time when the eyes are aligned
a patient with constant strabismus may alternate the eye that deviates, but typically one eye is preferred for fixation
contrast sensitivity
visual ability to see objects that may not be outlined clearly or that do not stand out from their background
the ability to see a shade of gray on a hwite background or to see white on a light grey background declines with age
lack of contrast sensitivity is not the same as blurred vision
contrast sensitivity is often referred to as
“functional vision” beyond how well you see details on a standard eye chart
low contrast sensitivity may result in
problems with night driving, including inability to see traffic lights or spot other cars and pedestrians
ppl w poor contrast sensitivity also may require extra light to read, and eyes may become tired when they read or watch tv
poor contrast sensitivity can cause you to stumble when you fail to see that you need to step down from a curb onto similarly colored pavement
low contrast sensitivity can be a symptom of
certain eye conditions or diseases such as amblyopia, cataracts, glaucoma, or diabetic retinopathy
sometimes occurs as a side effect of laser vision surgery procedures including LASIK and PRK
convergence
turning inward of the lines of sight to attain or maintain single vision
in the real world there is only convergence, unless fusion is prevented by mechanical or other reasons (such as strabismus)
we use the word “divergence” but it is a relative term, meaning that the eyes are relatively less converged than they were previously
5 types of convergence
tonic: normal muscle tonus present in the living eye
proximal: a “psychological” component, based on perceived awareness of the closeness of an object
accommodative: reflexly related to accommodation
fusional: stimulated by perceived disparity to attain or maintain single vision, usually occurs at sub-conscious level
voluntary: aligning the two eyes with conscious effort
why is convergence effortless
the various types of convergence are controlled by centers in different areas of the brain; all the components must be integrated if fusion is to be effortless
this allows conscious effort and attention to be directed elsewhere
convergence excess
more eso is measured at near than at far
convergence insufficiency
more exo is meaured at near than at far
convex lens
(plus lens) thicker in the middle than at the edges
plus lenses used to compensate for
hyperopia, or farsightedness
in the vt room, plus lenses are used to
cause changes in accommodation and convergence, and to help develop a better balacne between these two systems
convex lenses make objects appear
larger and further (the LO of SILO)
cornea
a transparent, avascular tissue at the front of the eye which is the first surface that light entering the eye passes through
the cornea forms a major part of the refractive, or “light bending” part of the visual system
normal correspondence
in normal binocular vision the fovea of the right eye “corresponds to” or is in “correspondence with” the fovea of the left eye
when corresponding areas of the retinas are stimulated by images of the same or compatible objects, the patient appreciates single vision, or fusion
these retinal areas are “matched” b/t the eyes and the stimulation of a pair of corresponding points gives rise to the same visual direction which the brain always localized in the same direction, whether or not the stimulus is actually from this direction or not
cortical level
at the conscious level of thought
cover test
a probe used by the optometrist to provide info about eye teaming
2 types of cover test
alternate cover test and unilateral cover test
alternate cover test
a test to detect the presence of a phoria or strabismus
patient’s attention is directed toward a small fixation target and one eye is occluded for several seconds,
the cover is then quickly moved to the other eye
if the eye that had been under the cover moves upon uncovering it, either a strabismus or phoria is present
unilateral cover test
a test to detect the presence of a manifest deviation (strabismus or tropia) in the alignment of the eyes
patient is directed to look at a small target with both eyes and then an occluder is used to cover one eye
the doctor monitors the movement (if any) of the non-covered eye: if there is movement, the presence of a strabismus (tropia) is indicated
crystalline lens changes its shape and power to achieve changes in accommmodation in response to
blur on the retina or a perceived change in distance of the object of regard
cyclopean eye
when looking with 2 eyes we see the world as if from a single point: this is called cyclopean vision, and the point is called the cyclopean eye
every perceived visual point has a single perceived visual direction from this cyclopean eye: egocentrically up-down-to the right- or the left.
Thus, binocular localization is integrated and referred to a point which represents the felt position of the body.
cyclotropia
a type of strabismus in which the vertical axis of the eye is rotated away from the vertical position
(this is often the by-product of surgical intervention)
cylinder
a type of lens which does not have uniform power throughout
there is a full power in one meridian of the lens, gradually decreasing in power to zero at a point 90 degrees away from the meridian of power
cylindrical lenses are used to compensate for
astigmatism
depression
aiming the eyes downward
diopter
a unit of measurement to designate the refractive or bending power of a lens or optical system
the term “diopter” is used in expressing measurement of both lenses and prisms
a one diopter lens (1.00 DS)
brings parallel rays of light to a point focus at a distance of one meter
a one diopter prism (1Δ)
displaces the image of an object 1cm at a 1m viewing distance
diplopia
the condition in which a single object is perceived as 2 objects instead of one, double vision
diplopia may be physiological or pathological
physiological: normal desired perception of double vision of a non-fixated object (eg. the brock string)
pathological: as in strabismus, when a fixated object is perceived as double bc the strabismic eye is not aligned upon it (the image of the fixated object falls on a non-macular area of the deviated eye and is not suppressed)
how does pathological diplopia happen
the simultaneous stimulation of non-corresponding or disparate retinal elements by a target, causes the target to be localized in 2 different subjective visual directions, and thus appears double
directionality
ability to correctly determine spatial directional properties of individuals, objects, and language symbols
dissociation
separating the binocular field into 2 monocular ones, for example when using dissociating prism to make the patient see double
divergence
the relaxation of convergence, allowing the 2 lines fo sight to become nearer to parallel, as the object moves away, as BI prisms are introduced, or as the patient looks to a more distant target
divergence excess
more exo is measured at far than near
divergence insufficiency
more eso is measured at far than at near
duction
an eye movement involving only one eye (i.e. monocular)
fundus
interior surface of the eye opposite the lens and includes the retina, optic disc, macula, fovea, and posterior pole
after a relay at the LGN in the thalamus, the retina sends its major neural output to the visual cortex (striate cortex)
this is called the
geniculostriate visual pathway
