Strabismus

Front 1

Define Strabismus

Back 1

Condition in which binocular fixation is not present under normal seeing conditions. Foveal line of sight does not intersect the object of fixation

Front 2

Name 4 synonyms for Strabismus

Back 2

1. Heterotropia
2. Tropia
3. Squint (old term)
4. Manifest deviation (latent deviations = phorias)

Front 3

Give some characteristics of Amblyopia

Back 3

1. Unilateral (sometimes Bilateral)
2. BCVA is less than 20/20
3. No structural or pahtological anomalies
4. Must have 1 or more of the following occurring before age 6:
a. Amblyogenic anisometropia
b. Constant unilateral strabismus
c. Amblyogenic bilateral isoametropia
d. Amblyogenic uni/bil astigmatism
e. Image degradation

Front 4

Give some misconceptions of strabismus/amblyopia

Back 4

1. Rare conditions
2. Only in children
3. Patients must see a specialist
4. Untreatable

Front 5

T or F? An amblyope has a higher risk of becoming blind than the general population

Back 5

True. 1.75/1000 vs. .66/1000 (adults)

Front 6

List some benefits of amblyopia treatment

Back 6

1. Safety factor - if one is damaged
2. Single vision
3. Improvement in cosmesis
4. Increased FOV
5. Stereopsis
6. VA increase
7. Kinesthetic improvement
8. Reduced psychosocial impact

Front 7

List some benefits to the practitioner

Back 7

1. Complete and valid diagnosis
2. Establish reasonable prognosis
3. develop an appropriate management plan
4. Intelligently communicate w/ pt/parent
5. Provide good patient management
6. Assure professional responsibility
7. Intellectually challenging
8. Personally rewarding

Front 8

List the components of normal binocular vision

Back 8

1. Healthy eyes and visual path
2. accurate monocular fixation OU
3. Accurate bifoveal fixation
4. Integrated neuromuscular coord of intra and extraocular neuromuscular systems
5. sensory correspondence system organized about the fovea as a center
6. similarity of final ocular images
7. sensory unification of the 2 ocular images

Front 9

T or F? A breakdown in 1 or more of the binocular system components leads to Anomalous vision

Back 9

True. Anomalies of strabismus divided into: Sensory and Motor anomalies

Front 10

List the components of a good Strabismic case history

Back 10

1. CC (cosmesis, failed SS, Signs/symptoms, visual discomfort, second opinion, + FOH)
2. Diplopia Hx: Mono/Binoc, Freq, image orientation, dist/near, 1st noticed, sx, stable thruout the day
3. Asthenopia: common in int. strab or large phoria, constant strab = less sx, more sensory anomalies = less sx
4. Time of onset: critical in determining prognosis (~50% begins < 1 yo and increases again > 50 yo)
5. Type of onset: Gradual vs. Sudden
6. PEH: Duration? Previous Tx?
7. FEH: Can run in families

Front 11

T or F? Infantile = Birth to 1 year and Acquired is > 1 yo

Back 11

False. Infantile = Birth - 6 mos
Acquired = > 6 mos

Front 12

Which strabismic conditions is the most common among Neonates?

Back 12

IXT up to 6 mos - ET develops between 2-4 mos

Front 13

Time of onset identified by patient/parent reports.....

Back 13

1. Sensitivity = 65%
2. Specificity = 99%
3. Not as accurate in children < 1 yr
4. Developmental period of poor binocular coordination (1st 2 mos)

Front 14

Onset also identified by... other than patient/parent reports

Back 14

1. Photographs - child must be looking dead on
2. Early exams -best confirmation

Front 15

Family transmission of strabismus is probably multifactorial - expression is determined by...

Back 15

1. how many of responsible genes present in each parent
2. what quantities of each factor are given

Front 16

List some risk factors for strabismus

Back 16

1. High AC/A
2. Hyperopia (>1.50D) (associated with ET)
3. Eso/exophoric tendency
4. Poor vergence ability
5. LBW
6. Maternal cig smoking (>2packs/day)
7. Maternal age for ET
8. Neurological abnormalities, seizure states, CNS and skeletal conditions

Front 17

Classification of Amblyopia is based on....

Back 17

the clinical condition responsible for its development. Classes:
1. Strabismic
2. Anisometropic
3. Isoametropic
4. Deprivation (image degradation)

Front 18

List some characteristics of Strabismic Amblyopia

Back 18

1. ~ 1/3 of all amblyopia
2. No relationship b/w depth of amblyopia and size of strabismus
3. Foveal line of sight fails to intersect object
4. Confusion (dissimilarity of image on foveas) & Diplopia --> lead to suppression and cortical spatial changes.
-Must be constant because if pt able to fuse sometimes - could be protective against amblyopia
-Strabismics at near do NOT develop amblyopia
-IXT does not cause amblyopia b/c not constant

Front 19

List some characteristics of Anisometropic Amblyopia

Back 19

1. ~ 1/3 of all amblyopia
2. Dissimilar retinal image, clarity, contrast, and size
3. Unequal input --> ABI --> suppression
4. Eye with higher RE becomes amblyopic
5. As aniso increases, generally greater decrease in VA
6. Correlation between amount of aniso and depth of amblyopia

Front 20

List some characteristics of Isoametropic Amblyopia

Back 20

1. From uncorrected high bilateral RE
2. Ret images have equal clarity/size but blurred
3. Bilaterally reduced VA
4. BCVA typically 20/30-20-60

Front 21

What RE could potentially cause Isoametropic amblyopia

Back 21

Hyperopia = >4.50D
Myopia = > 6.00D
Astig = > 2.50D

Front 22

Etiology of Deprivation Amblyopia?

Back 22

Physical obstruction along the line of prevents formation of well-focused, high contrast image on the retina
1. Congenital cataract
2. Media opacities
3. Sign. Ptosis
4. Prolonged occlusion

Front 23

Characteristics of Deprivation amblyopia

Back 23

1. Uni/Bil
2. Increased severity with Unilateral
3. Often Severe: VA loss (>20/200)
4. Less common than other types
5. B/c blurred - neural connections not stimulated
6. Primary effect cortical; basic retinal receptor processes normal
7. Spatial freq. channels present but require higher contrast to be activated

Front 24

List the 2 amblyogenic mechanisms

Back 24

1. Abnormal binocular interaction: ABI caused by unequal or conflicting input. Competitive, inhibitory effect leads to suppression
2. Form deprivation

-Both happen coritically

Front 25

T or F? The younger the child, the more susceptible they are to develop amblyopia

Back 25

True. Most sensitive from birth to 2-3 years, then decreases until ~ 6 yrs.
-Amblyogenic factor must be present all the time
-ABI effect may be more powerful

Front 26

T or F? Visual Acuity alone can diagnosis amblyopia

Back 26

False. Corrected acuity of amblyogenic eyes can fall within a range of normal acuity

Front 27

What are some problems with using VA as a amblyopic criterion

Back 27

1. Measured VA varies w/ test method
2. No clear cut-off
3. Amblyopes could have 20/25 VA!

Front 28

List some characteristic behaviors of an amblyogenic eye

Back 28

1. Response is slow, irregular
2. Wide range of acuity errors
3. Miscalls not necessarily confusion letters
4. Letters read out or order or skipped
5. Letters on ends easier than in middle
6. Isolated > single line> full chart
7. Variability makes repeatability testing poor

Front 29

What are behavioral responses to VA testing related to....

Back 29

1. Contour effects
2. Spatial distortion
3. Reduced CSF at high SF
4. Unsteady/inaccurate mono fixation
5. Eye tracking skills
6. Accommondation

Front 30

List 3 ways to assess VA on an amblyopic patient

Back 30

1. Snellen: single letter w/ crowding bars easiest; identify whether amblyopia present
2. ATS, HOTV and ETDRS: assign a reliable baseline VA
3. Interferometry: establish a reasonable prognosis

Front 31

Which technique is used to determine prognosis of amblyopic treatment

Back 31

Interferometry

Front 32

If Latent Nystagmus...

Back 32

Polaroid test, if nonstrabismic
High plus fellow eye

Front 33

Which two factors must be controlled when determining refractive status

Back 33

Scope on visual axis and control accommodation (best way = cycloplege)

Front 34

What happens to the sphere and cylindrical components of the RE when scoping off axis?

Back 34

Sphere decreases, astigmatism increases

Front 35

List the components of a Mohindra Retinoscopy

Back 35

1. Dark room
2. Occlude other eye
3. 50 cm WD
4. Pt looks at light
5. Subtract 1.25 D
6. NOT a substitute for Cycloplege
-Tends to underestimate Hyperopia

Front 36

List the characteristics of an ideal Cycloplegic agent

Back 36

1. Rapid Onset
2. Complete paralysis
3. Adequate duration
4. Rapid recovery
5. Absence of side effects

Front 37

T or F? Tropicamide is an excellent cyclo while Cyclopentolate is an excellent dilator

Back 37

False. Tropicamide is a good dilator but horrible at controlling accommodation. Cyclopentolate is good at paralysis but doesn't dilate well.

Front 38

What is the ideal cycloplegic agent?

Back 38

Cyclopentolate 1% (for > 1yr)
-For < 1yr use .5% Cyclopentolate

Front 39

List the correct sequence for administering a cycloplegic agent

Back 39

1. Topical anesthetic
2. 1 gtt cyclopentolate
3. Wait 5 min
4. 1 gtt cyclopentolate
5. Refraction: Dark iris - 30-40 min; Light iris - 10-15 min
-Tropicamide or Pheny for DFE

Front 40

List some Indications to cycloplege a patient

Back 40

1. Esotropia
2. Amblyopia
3. Mod - Hi hyperopia
4. > 1.00 D aniso
5. Suspected latent hyperopia
6. Suspected Pseudomyopia
7. Uncooperative or noncommunicative patients
8. Malingerer
9. Hysterical amblyopia
10. Acuity not to projected level
11. Subjective responses inconsistent
12. Sx seem unrelated to nature/degree of manifest ref
13. First eye exam for child

Front 41

List some methods for double checking the adequacy for the Cycloplege (<2.00D amps)

Back 41

1. Watch Ret reflex for variation
2. Read 20/20 at near?
3. MEM > 2.00D lag
4. Accommo Amps < 2.00D
5. Most plus to BVA w/ threshold snellen line at distance
-add minus monocularly
-if < 0.75 D decrease VA then OK cyclo
-Do NOT use pupil size!!

Front 42

List some DDx of reduced VA

Back 42

1. Functional amblyopia
2. Uncorrected RE
3. Organic vision loss: Nutritional amblyopia, Toxic amblyopia, Ocular pathology
4. Psychogenic/Hysterical vision loss
5. Malingering

Front 43

T or F? Functional amblyopia is a development disorder than can develop after the age of 6

Back 43

False. Form vision development is complete by the age of 6 so amblyopia cannot develop after

Front 44

List two causes of bilateral organic amblyopia

Back 44

1. Nutritional: symmetrical, painless, Central (80%), Acquired color (RG) loss (50%), possibly pallor in late phases
2. Toxic: Sudden, VA loss, Central scotoma, Exogenous of Endogenous causes
-Both: Lesion - ganglion cell layer degeneration w/ secondary ON fiber layer atrophy

Front 45

List some characteristics of Psychogenic/Hysterical Amblyopia

Back 45

1. Alteration in sensory or voluntary motor functioning that suggests neurological
2. Characterized by substitution of physical signs/sx for anxiety or emotional repression
3. Psychological factor is judged to be associated w/ symptom b/c started or got worse after stress
4. Sx not produced consciously or intentionally
5. Sx cannot be fully explained by a medical condition

Front 46

List the typical presentation of a patient with Hysterical/Psychogenic amblyopia

Back 46

1. Female, 8-14 yrs
2. cc: blurred vision or no complaints
3. No prior vision problems or Rx
4. Hx includes possible psychogenic cause

Front 47

Psychogenic Vision Loss Findings...

Back 47

1. Bilateral and typically equal decrease in VA
2. Not related to RE
3. Not from functional amblyopia
4. Normal ocular health
5. Constricted VF - tubular, spiral
6. Often 20/20 w/ little or no SRx

Front 48

List some characteristics of Tubular VF in psychogenic amblyopic patients

Back 48

1. Bilateral, constricted, circular
2. Pathognomonic of hysteria
3. No organic disease produces
4. These patients not conscious of it or would limit motility
-Malingers usually do not fake VF

Front 49

How do you diagnosis Psychogenic Vision loss

Back 49

-R/O RE and Ocular pathology
-Bilateral decrease in VA
-Tubular visual fields
-History

Front 50

List the characteristics of Streff Non-Malingering Syndrome

Back 50

1. Decreased VA (near> far)
2. Decreased WD
3. Minimal RE
4. Decreased stereo
5. Color vision distortion
6. Hi or unstable Lag of Accommo
7. VF contracted or spiraling
8. Females 2:1
9. No specific emotional stress

Front 51

T or F? It can be assumed that VA cannot be improved in amblyopic eye w/ coincidental oraganic problem

Back 51

False. VA can be improved unless decrease in VA is due entirely to organic problem

Front 52

Normal Fixation depends on the following....

Back 52

1. Best visual acuity at the fovea
2. Principal visual direction @ fovea
3. Zero retinomotor value @ fovea

Front 53

Define the Principal Visual Direction (PVD)

Back 53

Straight ahead visual direction subjectively associated w/ point of fixation. Serves as direction of reference for all other visual directions. Normally at the fovea

Front 54

Define the Retinomotor Value (RMV)

Back 54

Value assigned to a retinal receptor indicating its angular distance and radial direction from fovea. Amount of electrical signals brain uses to tell eye to put fovea on target
-Normally, RMV increases from fovea to periphery

Front 55

T or F? Monocular fixation is present in all strabismic amblyopic eyes

Back 55

False. Monocular fixation is only present in amblyopic eyes and only in strabismic amblyopic eyes some of the time
-Almost always unilateral

Front 56

List the three characteristics of EF that you record

Back 56

1. Location: NTSI or paradoxical
2. Magnitude: most < 3D; not associated with angle of strab
3. Stability: Steady?

Front 57

If a patient presents with Decreased acuity in one eye but shows not movement on the CT - how could you determine if they have a EF

Back 57

Use Visuoscopy

Front 58

T or F? More peripheral the EF --> the more stable

Back 58

False. more peripheral = less stability

Front 59

T or F? Typically the RMV and the PVD are associated with the same point

Back 59

True. Typically the case with EF

Front 60

T or F? PVD is at a non-foveal point when a patient is eccentrically viewing

Back 60

False. PVD is at the fovea. Ex. MacDeg patient uses peripheral fundus to view b/c fovea has decreased VA. PVD is still at the fovea in this case

Front 61

List the two Objective testing methods for EF. List the two for Subjective testing

Back 61

1. Visuoscopy
2. Angle Kappa

1. Haidinger's Brushes
2. Brock-Givner AI transfer

Front 62

T or F? Brock-Givner AI transfer is based on the assumption that the patient has NRC

Back 62

True. Because the AI tags the fovea of the good eye and is cortically transfered to the fovea of the other.

Front 63

Angle Kappa is the angle between the pupillary and visual axis. T or F?

Back 63

True. Can only detect huge amounts of EF

Front 64

What is the mean amount of Angle Kappa

Back 64

~ 0.5 mm nasal (common still abnormal)
-Why is this? Fovea is temporal to pupillary axis

Front 65

Describe the Angle Kappa technique

Back 65

1. Pt monocularly fixates
2. Dr. is monocular and evaluates reflex relation to pupil center: Nasal = +, Temp = (-). Compare to fellow eye
-If angle OD = angle OS suggests no gross EF
-If amblyopia and angle OD does not equal angle OS suggests large EF
-1mm = 22 prism diopters - hard to see estimate small deviations

Front 66

List two uses for Angle Kappa

Back 66

1. Diagnose large amounts of EF
-Abnormal >K may simulate, conceal or exaggerate a deviation
2. Necessary for Hirshberg interpretation

Front 67

How is EF related to VA?

Back 67

Decreased VA with increased eccentricity from fovea.
VA of amblyope w / EF decreased more than expected from EF alone
Why? because amblyope has a motor and sensory component

Front 68

List 2 mechanisms for decreased VA

Back 68

1. Motor (EF)
2. Sensory (Inhibition)
-VA different for 1st 10 deg due to sensory decrease. Past 10 deg, all motor loss - no more sensory.
-VA at fovea of an amblyopic eye still lower than normal eye

Front 69

Give the formula to calculate VA decrease from EF in amblyopic eye

Back 69

MAR = EF + 1
20/X = 1/MAR

Front 70

T or F? Can predict EF from VA

Back 70

False. VA decrease can be due to sensory and motor dysfunction and EF only from motor

Front 71

List three etiology hypothesis for EF

Back 71

1. Scotoma Hypothesis: VA at fovea is worse so use surrounding retina (EF) to enhance resolution
2. Monocular Manifestation of AC: Under mono viewing, EF pt used to fixate is same spot as anomalous point under binoc viewing conditions. <D=<A=<E
3. Motor Theory: Constant unilat strab - excessive innervation of agonist EOM. Occlude non-strab eye -- tonic innervation persists -- small error in eye position

Front 72

Clinical Testing Strategy

Back 72

1. Screen for gross EF using angle Kappa
2. Visuoscopy
3. If no foveal reflex or to confirm data-->Haidingers brushes; BGAIT test (only if NRC)