Introduction/Evaluation Flashcards
___% of strabismus patients develop amblyopia
50%
What percentage of patients whose chief complaint is an eye turn actually have strabismus?
50%
Incidence of strab in children
3-4%
What magnitude of deviation is found in infantile ET?
35-40 ∆
Age of onset for Infantile ET
Birth to 6 months
Age of onset for Accommodative ET?
2-3 yrs
when toddler begins exploring near world
In the first few months of life, infants come exhibit variables amount of strab.
What magnitude and at what age is this finding normal and thought to resolve over time 25% of the time?
< 30 ET between 3-6 months will resolve 25% of the time
Characteristics of an eye turn
FLORIDA
Frequency
Location
Onset
Relieving Factors
Intensity
Direction
Associations
A premature baby is born before ____
37 weeks
What is a low birth weight?
< 1500 g or 3.3 lb
What is an abnormal APGAR score?
≤ 6
APGAR score is based on
- Skin color
- Pulse rate
- Reflex response
- Muscle tone
- Breathing
Birth History pertinent to Strab/Amblyopia (6)
- Premature birth
- Low birth weight
- Low APGAR score
- Prenatal morbidity
- Substance abuse/smoking
- Older maternal age
What is considered an older maternal age?
> 30 years old
Developmental Hx pertinent to Strab/Amblyopia
- Craniofacial anomalies
- Neurodevelopmental impairment
- Down Syndrome
- ROP
2 Ways to Assess Amblyopia Treatment Prognosis
- 2.0x Telescope
- Neutral Density Filter
Amblyogenic Factor: Isometropia Astigmatism
> 2.5 D
Amblyogenic Factor: Isometropia Hyperopia
> 5 D
Amblyogenic Factor: Isometropia Myopia
> 8 D
Amblyogenic Factor: Anisometropic Astigmatism
> 1.5 D
Amblyogenic Factor: Anisometropic Hyperopia
> 1 D
Amblyogenic Factor: Anisometropic Myopia
3 D
UCT determines
Presence/absence of strabismus
ACT determines
Direction and magnitude
Testing distance for Hirschberg/Krimsky
50-100 cm
Testing Distance for Bruckner
75-100 cm
3 reasons for false positives in Bruckner
- Anisocoria
- Significant Anisometropia
- Unilateral media opacity
4 Tests to assess Ocular Alignment
- CT
- Hirschberg/Krimsy
- Bruckner
- 4 BO Test
Why are objective tests more appropriate to test ocular alignment than subjective tests?
Pt may have developed anomalous correspondence
4 BO Test:
Prism placed in front of the left eye and there is no movement. What is the result? Does this confirm a microET?
(+) 4 BO Test OS
No, 4 BO Test does not confirm the presence of a strab; it only confirms presence of suppression.
4 BO Test:
Prism placed in front of right eye
Both eyes move the the left
Left eye then moves to the right
What is the result?
What happens if you switch the prism to the other eye?
(-) 4 BO Test OD, OS
Same results; a version followed by a duction confirms suppression in neither eye
RECTUS muscles insert at a ___º angle and ____ the equator
20º
In front of
OBLIQUE muscles insert at a ___º angle and ____ the equator
50º
Behind
Hering’s Law are in reference to ____ (synergists/antagonists)
Synergists
Sherrington’s Law are in reference to ____ (synergists/antagonists)
Antagonists
In a palsy of ____ onset, secondary deviation is larger than primary. Why?
RECENT; Hering’s
Primary deviation is measured when which eye is fixating? (Affected/Unaffected)
Unaffected
Secondary deviation is measured when which eye is fixating? (Affected/Unaffected)
Affected
3 Reasons for EOM underaction/overaction
- Innervation deficiency (CN 3, 4, or 6)
- Mechanical reasons (faulty muscle insertion restricting movement)
- Paretic EOM (e.g. trauma)
What is the difference between an ocular torticollis and congenital torticollis?
Ocular torticollis — head tilt due to visual issue (resolves w/ correction)
Congenital torticollis — abnormal head/shoulder mm.
(+) Forced Duction Test means…
The eye did NOT move —> mechanical (e.g. muscle entrapment)
(-) Forced Duction Test means…
Muscle was able to move —> innervational issue
3 Tests to test Comitancy
- Hess Lancaster
- CT in 9 Gazes
- Red Lens Test in 9 Gazes
Parks 3 Step must always be conducted when ___
Presence of vertical deviation
What are the 3 steps in Parks Three Step?
- Which is hyper in primary gaze
- Which gaze makes the deviation worse?
- Which head tilt makes the deviation worse?
Why must you perform retinoscopy monocularly?
An eye turn will cause a pt to appear more myopic
TRUE/FALSE: unsteady fixation is seen in both CF and EF
TRUE
Rank these in order from Best VA to Worst VA:
1. Steady CF
2. Unsteady CF
3. Steady EF
4. Unsteady EF
Best VA
|
1. Steady CF
2. Unsteady CF
3. Unsteady EF
4. Steady EF
|
Worst VA
3 tests to assess Fixation
- Brock After Image
- MIT
- Visuoscopy
Formula for determine approximate VA for EF
VA = 20 / [20(1+PD)]
Example: 3 PD EF
20 ( 1+3 ) = 80
Estimated VA: 20/80
What (in the retina) causes Haidinger’s Brush?
Xanthophyl in Henle’s Layer (around the fovea)
MIT:
OD is occluded
OS is open
OS views brush 2 cm left of fixation
What is the EF?
2 PD temporal EF
Which eye is flashed during Brock After Image?
NON-amblyopic eye
TRUE/FALSE: Patients will mild amblyopia may still have stereopsis
TRUE
First Degree Fusion
Superimposition — can perceive two dissimilar targets as occupying same visual direction
Second Degree Fusion
Flat Fusion — fusion w/o stereopsis
Third Degree Fusion
Stereopsis
Horror Fusionis
Inability to fuse two images —
Approaching targets seem to slide of jump without apparent fusion or suppression
W4D:
Why might a patient that suppresses OS (sees 2 red dots only) at a distance of 6 m, perceive fusion when retested at 33 cm?
At 6m, suppression zone is larger than target angle
At 33 cm, the target angle is larger than the suppression zone
TRUE/FALSE: size of suppression zone is independent of room lighting
FALSE
TRUE/FALSE: pts often develop both suppression and AC
TRUE
Name 2 tests of motor fusion
- BI/BO range
- NPC
