Midterm 1 Flashcards
Define phoria
when both eyes are uncovered, both point toward the object of regard
What happens during cover test for a phoria?
when an eye is covered the eye moves out of alignment and when uncovered, alignment is quickly restored
What does a phoria tell us?
how the person is habitually calculating space
Define strabismus
when both eyes are open and uncovered, one eye is pointed at the target and the other is pointed somewhere else
What differentiates phoria with refixation from tropia?
tropia is when eye does not align after first blink (harris) or after 10 sec (bodack)
What is the old definition of amblyopia?
best compensated visual acuity is 20/40 or worse in either or both eyes
What is the newer definition of amblyopia?
best corrected visual acuity is 20/40 or worse in either or both eyes OR there is more than a 2 line difference between the two eyes
Why was the amblyopia definition updated?
to include some 20/25 to 20/30 best compensated eyes in the definition
What does Kraskin say about amblyopia?
amblyopia as a binocular dysfunction manifesting as amblyopia
How do the two channels often differ with amblyopia?
there may be specialization b/w the 2 channels: what and why activities
Which channel takes the lead for what activities?
the fellow eye
Which channel takes the lead for where activities?
the amblyopic eye
T/F it is irrelevant to talk of a good eye or bad eye
true, both channels have given something up in order to perform certain tasks better
What is the amblyopia prevalence in the military, school children, and patient’s seeking vision care?
1.6%, 1.8%, 2.3%
Define eccentric fixation
looking with the line of sight away from the fovea in an otherwise healthy eye
How will steady EF manifest with an ophthalmoscope?
the fovea will remain in the same or nearly the same relation to the axis of fixation
How will unsteady EF manifest with an ophthalmoscope?
the fovea will appear to move relative to the axis of fixation
What is the majority of fixation cases?
steady central
What is the hardest fixation to treat?
steady eccentric
Which fixation case has variable VAs?
unsteady central
What degrees do foveal center, foveal off-center, and parafoveal EF correspond to?
0, 0-1, and 1-3 degrees
What degrees do paramacular and peripheral EF correspond to?
3-5 and >5
What is the expected acuity for 1/2 degree off foveal center and 1 degree off?
20/25 and 20/30 respectively
What is the expected acuity for 2 degrees off foveal center and 3 degrees?
20/40-20/50 and 20/50-20/60 respectively
What is the expected acuity for 4 and 5 degrees off foveal center?
20/60-20/70 and 20/70-20/100 respectively
What is the expected acuity for 10 degrees off foveal center?
20/100-20/160
What is the expected acuity for 20 degrees off foveal center?
20/180-20/300
If a patient’s EF is 3 degrees and their VA is 20/100, what does that mean?
EF only accounts for acuity of around 20/50 and the other acuity loss is due to a sensory component such as suppression
Define eccentric viewing
the person uses a point near the fovea to look with due to a loss of vision (something is wrong with the eye); loss can be optical, retinal or neurological
What is pleoptics?
a method of treating amblyopia with eccentric fixation, which consists of dazzling the eccentrically fixating retinal area with high illumination while protecting the fovea with a disc projected onto the fundus and thereby rendering the fovea more responsive to fixation stimuli
What is the prevalence of amblyopia and/or strabismus in the population?
4-6%
What is the ratio of eso deviations to exo?
eso is far more frequent than exo, ratio 3:1
T/F amblyopia has been reported to occur in 5-13% of concomitant exotropes
true
What strabismus and refractive error is common in infantile onset (birth to 6 months)?
85% esotropes w/ mean of 40 pd, most plano to +3
What is the reason that is most prevalent for adult onset strabismus?
paralytic, often stroke
T/F strabismus leads to decreased binocular summation and binocular inhibition
true, strabismus may impair visual function more than previously appreciated
T/F children with a history of amblyopia, even if resolved, exhibit impaired visual auditory integration and perceive speech differently
true
How does strabismus impact employment?
orthophoric women got greater hiring preference than ET/XT women, no preference for males
What is one key to helping strabismics/amblyopes?
if we understand why the person learned to use the visual process in the way they have (asymmetric), then the treatment follows
For what purpose does vision develop?
so humans can use their two eyes to develop reliable basis for action aka derivation of meaning and direction of action
___% develop normal binocularity
95%
When does confusion result?
when there is sensory conflict between the two visual axes
What happens to confusing visual information?
it is suppressed as part of the normal mechanism of seeing
What happens with suppression in amblyopia or strabismus?
relatively deep suppression becomes habitual and these behavior patterns become the norm
Why does strabismus and/or amblyopia develop?
to provide a reliable visual basis for directing action when the person has not acquired the skill to do so with symmetrical fixation
How do strabismus and/or amblyopia patients preserve binocularity?
they preserve binocularity over the majority of the visual field by making it easier to rely on the central flow through one visual channel
What is the white noise concept of behavior?
the infant is constantly trying different ways of using their hardware and constantly display a wide array of behavior patterns
What is the eye’s posture at rest?
exo
What is true of exodeviations in neonates?
transient neonatal exodeviations normally occur in the first few months of life and are consequent to developing ocular alignment and control
What is Donald Hebb famous for?
nerves that fire together wire together aka positive patterns of behavior lead to longterm potentiation
How do infants develop their binocular system?
as the developing child interacts with the environment, there will be brief encounters that result in the short term amplification of signals in the system… this reinforces the connections that are involved in that behavior and builds neurology
T/F unsuccessful behaviors are repeated
false, successful patterns of behavior are repeated and used for as long as they remain successful
Why might an eye turn develop?
at certain key points in development something gets in the way of a bilateral or binocular experience and the pattern found solves that problem in an asymmetric way
Infants seek ____
stimulation, this is the basis of preferential looking
The drive for meaning which results from binocular experiences _____
produces amplification of something important which serves to increase signal within the brain for use by the rest of the system
What is amplification useful for?
increases the potential to detect changes (JNDs)
T/F newborns exhibit all visual behaviors that change from moment to moment
true, at birth and infant does not use the binocular system like an adult
Bilaterality in the first weeks of life can be characterized as being primarily ___
reflexive
Where is accommodation fixed from birth to 3 months?
5D aka 20 cm
When should a child have control of the mechanism of accommodation?
by 6 months
We are a b____ b_____ organism
bilateral, binocular
Asymmetries in ___ are reflected in asymmetries in ___
bilaterality, binocularity
What is the general flow of asymmetry in the body?
asymmetry of the body leads to asymmetric use of the visual system
Do asymmetries in binocularity cause the development of asymmetries in the bilateral use of the body?
yes, but usually due to trauma or disease causing retrograde bilaterality problems
Is knowing the etiology of strabismus and amblyopia important?
yes, it can help to determine the level of prognosis and how long it will take to achieve that goal
What does congenital mean optometrically?
born with
What does infantile mean optometrically?
occurred during the first year of life
Is incidence of true congenital strabismus high or low?
very low
What is the butterfly effect?
sensitive dependence on initial conditions, aka small changes can have big consequences
What is likely to develop from challenges b/w 3-6 months of age?
high angle (>40-45 D) unilateral esotropia with deep amblyopia (20/200-20/300)
What is likely to develop from challenges b/w 6 and 18 months?
high angle (>40-45 D) esotropia without amblyopia
What is likely to develop from challenges b/w 18 and 30 months?
moderate esotropia or exotropia (blindspot tropia) and unilateral refractive amblyopia
What is likely to develop from challenges b/w 3-5 years?
accommodative esotropia, high plus (+4 to +7)
T/F hyperopia is causative for strabismus
false, hyperopia is just a risk factor
T/F we see amblyopia in exotropes
false, no amblyopia in exotrope unless from consecutive exotrope s/p surgery
What does low tone/energy in an infant result in?
weak convergence from natural at rest position of the eyes
What does exotropia have a positive correlation with?
onset prior to age 2, alternating, hypoxia at birth, delayed developmental milestones, neurologic involvement
What is the most prevalent XT?
73% intermittent and 56% basic rather than CI/DE
Define concomitant
when the person looks in different directions of space the eyes stay in the same relative position to each other, all movements are yoked
What does a concomitant tropia look like?
tropia will be the same in all gazes (within a few pd)
Define non-concomitant
when the person looks in different directions of space the eyes change their relative positions to each other
What does a non-concomitant tropia look like?
tropia measurements are different in each gaze
What is the impact of strab surgeries?
most surgeries alter geometry and produce scar tissue; prognosis is better if they have no had any surgery, even if post-op the amount of turn is small
What is optometric paralysis?
loss or impairment of muscle function or sensation (will lead to non-concomitance)
What is optometric paresis?
incomplete or partial paralysis (will lead to non-concomitance)
What is optometric palsy?
paralysis, especially in reference to special types
What is the difference between non-concomitant and palsy/paresis/paralysis?
non-concomitance may result from mechanical restrictions but the three Ps relate to the muscles only
What are the pairs of contralateral synergists?
LR/MR, SR/IO, IR/SO
What are the homolateral antagonists?
MR and LR, SR and IR, SO and IO
Is underaction or overaction more common?
under
What changes result with new paresis/palsy?
underaction of involved muscle and contracture of homolateral antagonist/contracture of contralateral synergist
What happens with a paresis of RSO?
contra contracture LIR, homolateral antag RIO
What happens with a paresis of LSR?
homolateral antag LIR, contra contracture RIO
Which nerve palsy is most prevalent?
6th
Which paretic strabismus is more concerning, acute or chronic?
acute, a diligent search for the cause is indicated including medical and neurological investigation
Describe paretic strabismus
sudden onset, any age, commonly c head trauma, noncomitant except in late stages, abnormal head posture, diplopia, uncommonly amblyopia, potential neurological finding or systemic disease
Describe nonparetic strabismus
gradual onset or shortly after birth/during childhood, uncommon to have head trauma, comitant, normal head posture, no diplopia, commonly amblyopia, systemic disease typically absent
Describe recent onset strabismus
constant diplopia, image tilting with CN IV palsy, noncomitant, absent contracture of antagonist, abnormal head posture until eye is covered, no amblyopia
Describe congenital/longstanding strabismus
diplopia rare, no image tilting, potential contract of antagonist, slight abnormal head posture currently and in old photos, potential amblyopia
Describe A syndrome
as the person looks in lower positions of gaze the eso deviation is less
Describe V syndrome
as the person looks in lower positions of gaze the eso deviation is larger
What adaptation might patients with A or V syndrome demonstrate?
patient may shift head up or down to find positions that aid their ability to use vision at the moment
What is the frequency of A and V types?
most common to least common V eso, A eso, V exo, A exo
What is the compensation for A eso and V exo?
chin elevated
What is the compensation for V eso and A exo?
chin depressed
What is DVD?
dissociated vertical diplopia, under some conditions when you cover one eye, the eye that is covered drifts upward, when you switch the cover to the other eye the newly covered eye goes up relative to the other, HIGHLY non-concomitant
What are other names for DVD?
alternating cirsumduction, dissociated vertical deviations
What is a DVD commonly an artifact of?
esotrope surgery or trauma
Is DVD a barrier to successful outcomes?
no
What is true of DVDs and visual field constriction?
when the total amount of visual field that a patient can use is restricted the patient may go into one or the other deviation patterns
What is peripheral fields good for?
helps us lock our two channels together
How many esotropes in the ophthalmology study had DVDs 10 years after surgery?
92%
What is resection?
tightening of EOM to add strength, can either cut muscle section out and sew together or move the attachment point forward
What is recession?
weakening of EOM, can move attachment backward or use botulin toxin to temporarily weaken muscle
Why use botox on EOM?
short term paralysis of EOM to allow ipsilateral antagonist to gain an advantage for cortical fusion
How long does botox work?
peaks at 5-7 days and lasts 3-8 months
What are other uses of botox?
reduce lid retraction in endocrine exophthalmos, reduce blepharospasm, temporarily eliminate wrinkles, reduce migraines
What is “orthotropia”?
surgical term for +/- 10 pd of orhtophoria
What is the success rate of strab surgeries?
16-43%
What is the surgical dosage with strab surgeries?
amount you want to recess
How are ear aches and CN VI palsies related?
CN VI travels near the mastoid which is connected to the ear, an infection can cause a temporary decrease in nerve conduction to the muscle causing an under-action of the muscle, setting up a situation which needs to be addressed
What are approaches to addressing ear aches and palsies?
face turn, send out more signal, suppress the eye, let the eye go in
What are critical times for ear aches?
critical visual development and development of bilaterality and binocularity is often birth to 6 months (prone) and 6-18 months (upright) these are critical periods for ear aches and eye turns
What is torticollis?
frozen head tilt, resulting in eyes that are not level, typically develop vertical deviations
How many torticollis patients develop strabismus?
2/3rds
What is VOR for?
stability of fixation
How many patients with tibia torsion develop strabismus?
2/3rds to 3/4ths
How are tibia torsion and strabismus connected?
tibia torsion is often treated by restricting the legs and feet, this results in no push off reflex and decreased opportunity to work on reciprocal interweaving
What is a functional leg length difference?
actual leg length is the same but when standing, hip rotates to one side and the gait changes, may result in head tilt and possibly a vertical eye deviation
What is horror fusionis?
constant double vision
What does cerebral palsy teach us?
work towards equality and use the more relaxed and more mobile side to guide the opening up of the restricted movement side aka if you want to get something to move in one direction, generally you have to move in the opposite direction to start
Define diplopia
the conscious awareness of seeing two images of a single object, which appear in two different areas of space at the same time
Define confusion
each eye is directed toward a different object, confusion occurs when the images of the two different objects compete to be represented on the internal representation of reality for the same location in space at the same time
What is more devastating, diplopia or confusion?
confusion, it drives change; causative factor of strabismus
Where does most suppression occur?
in the foveal or parafoveal areas, much of the visual info from the periphery is still used
Why is strabismus and/or amblyopia developed?
to preserve binocularity, not give it up
What are the general ways of resolving confusion?
tune on channel out (suppression), physically cover an eye, blur one channel, shift the relative position of the two images (eye turn), reprogram the directional sense of one eye
Expand on suppression to resolve confusion
generally only portions of one channel of flow is tuned out, suppression occurs early in the neurology and costs a good deal of energy to shut down the flow through one channel
Expand on blurring one channel to resolve confusion
patient may develop a single sided refractive condition
Expand on shifting the relative positions of the two images to resolve confusion
one eye can turn more or less, exotropia may develop two areas of space that can perceptually be used simultaneously (Flax hypothesis); medium eso finds the blind spot and large eso uses the nose as an occluder
Expand on reprograming the directional sense of one eye to resolve confusion
may emerge and be seen in some testing as anomalous retinal correspondence or anomalous projections, traditionally the whole eye gets reprogrammed aka it is a wiring problem and cheap energy solution
