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Strabismus 106 > Investigating Esotropia > Flashcards

Investigating Esotropia Flashcards

1
Q

What do you have to consider during VA testing of ET?

A
  • Observe for bhrs & objections
  • Age-appropriate (picture tests underestimate level of VA in comparison to letter test)
  • Crowded tests are more sensitive to amblyopia
  • Reliability of tests e.g. preferential looking may be considered less reliable
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2
Q

How does the ocular motility look in Esotropia?

A

Muscle imbalance; inferior oblique over-actions or lateral rectus function reduced

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3
Q

Which type of ET is ocular motility the most important?

A

Late-Onset ET (Acute-Onset / Normo-Sensorial)

  • Uncommon presentation of ET
  • Must exclude 6th nerve palsy (Abducens)
  • (Year 2) - disruption of fusion, decompensation and uncorrected refractive errors
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4
Q

What does convergence & accommodation look like in ET?

A
  • Convergence with reducing deviation can indicate potential for BSV at the intersection
  • Over-convergence of deviating eye to 6cm
  • Spontaneous divergence of the deviating eye
  • Assess near point of accommodation & amplitude
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5
Q

What will Bagolini glasses / Worth’s lights show in ET?

A
  • Suppression response
    or
  • BSV response if deviation is corrected, or in some cases of small angle ET
    or
  • Diplopia response (homonymous)
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6
Q

What are the testing conditions for Bagolini glasses / Worth’s lights in an ET?

A

Tested near and distance, with and without glasses AND tested in free space with prism at corrected angle

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7
Q

Using the Synoptophore, in an ET what shows potential for BSV?

A

Potential for BSV would be in the simultaneous perception slides the OBJECTIVE angle equalling the SUBJECTIVE angle.
If unable to do move the lion into the cage with any size slides = no BSV potential

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8
Q

If someone has a low fusion range in an ET, what is does this increase their risk of?

A

Increased risk of decompensation e.g. in losing BSV with an ET or they become constant when previously an intermittent ET

If unable to do a 20PD test then do a 15BO or a 10BO reflex test

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9
Q

What must we consider for Stereopsis testing in an ET?

A
  • Level of sensory and motor fusion
  • Age of the patient and comprehension
  • Dissociative properties of the test
  • Reliability of test
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10
Q

What do we do for Ophthalmology/ Optometry in an ET?

A
  • Fundus & Media Check
  • Cycloplegic Refraction
  • Fixation Visuscopy / Ophthalmoscopy (describe location i.e. central or eccentric and reflex i.e. steady or unsteady)
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11
Q

What is the Prism Adaptation Test (PAT) used for in ET?

A
  • To determine the maximum angle of deviation before surgical correction
  • Aim to fully correct or slightly over-correct
  • Emphasise importance of full-time wear of glasses with prisms
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12
Q

How do we conduct a PAT for an ET?

A
  • Measure deviation size for near & distance
  • Use Fresnel prisms to fully or slightly over-correct deviation for distance with Fresnel prisms and split between the two eyes. If the deviation is large for near, over 10PD, near angle should be corrected instead.
  • Measure deviation size again to ensure full correction before sending the patient home
  • Review in 1-2 weeks to reassess BSV potential and measure deviation size
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13
Q

What are the results of the PAT test?

A

1) Prism Responder = Residual microtropia with BSV without bifoveal BSV
2) Prism Responder = Visual axes straight with BSV
3) Prism Non-Responder = May have ARC ‘eat up’ the prism and return to their original angle = no BSV
4) Prism Non-Responder = May suppress or lack BSV

If a responder = operate on maximum angle of deviation

If a non-responder = operate on the original angle of deviation

I.e.
1) 0-8ET after Fresnels = Stays the same ET or have a slight microtropia

2) Become XT = non-responder

3) Start to “eat up” the prism – if you increase the Fresnel does it stable out? If over 60PD = non-responder, but if they get fusion with the larger Fresnel they are a responder

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14
Q

What do we have to consider to ensure the suitability of PAT to the patient?

A
  • Children from the age of 3 years
  • Require equal/near equal VA
  • VA of 0.300 logMAR (6/12) or better
  • Angle of deviation ≤40Δ
  • No vertical deviation (cannot mix horizontal and vertical Fresnels)
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15
Q

How do we investigation suppression density in an ET?

A

Density
- Sbisa bar
- Repeat at each visit when treating amblyopia

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16
Q

How do we investigate suppression area in an ET?

A

Area
- Prisms or synoptophore
- Post-operative diplopia test (PODT)
- Identify risk of diplopia after surgery or
botulinum toxin (BT) injection

17
Q

How often should we test for suppression in a child aged >5 years and why?

A

At each visit to prevent the risk of intractable diplopia

18
Q

Why do we investigation suppression before doing surgery on a patient with an ET?

A

Patient with ET and know they wont get BSV, need to check before straightening the eyes that they would still suppress and not get irretractable diplopia

19
Q

How do we test for central suppression in an ET?

A

Using a 4PD BO/BI Reflex Test

  • Assesses the presence of bi-foveal fusion or central suppression

We may then use Visuscopy to confirm the presence of eccentric fixation in microtropia with identity
(Garretty, 2021 means a moderate agreement between 4PD and Visuscopy)

20
Q

What is Aniseikonia?

A

Difference in image size.
So if someone is anisometropic then the image will be less magnified in the aniso eye. To combat this they may centrally suppress (without having a microtropia) as a sensory response.

21
Q

When would we do the Post-Operative Diplopia Test (PODT)?

A
  • Only do this where there is no demonstrable potential for BSV
  • Must be old enough for subjective testing (outside the critical period, varies with what we think for the sensitive period)
  • For assessing the risk of post-op diplopia
  • Predictive of surgical outcomes
22
Q

How do we conduct the PODT in ET?

A

Using prisms in free space at near and distance with glasses

  • Under & over-correct the angle of deviation up to 20PD
  • Assess risk of moving image out of suppression scotoma and thereby causing intractable diplopia
  • Record prism at which diplopia appreciate or graphic method

When appreciate diplopia – most suppress up to and/or over the corrected angle, some may have a risk around the corrected angle (so be careful with the full amount of corrective surgery).

23
Q

Why is AC/A ratio important in ET?

A
  • Differentiate accommodative types of esotropia at near (as Nr ET doesn’t have a high AC/A but convergence excess does)
  • Indicates suitability for bifocal therapy
  • In ET it’s often at least >8:1 but can be 15:1 sometimes
  • Nr ET isn’t improved through a +3.00 lens as eliminating accommodation has no effect at near as an AC/A ratio issue
24
Q

How is CBA used in ET?

A

CBA is the max VA obtainable while maintaining binocular single vision at near and distance for BEO. It assesses the control of deviation in relation to accommodative effort so is good for intermittent ET.
Is there a relationship between how much the patient is focusing or does it break down to an ET? As letters get smaller, have to focus more and so the eye may turn in. E.g. Intermittent ET, do quick CT and see straight eye, get them to read lower N print = breakdown and become ET. This tells us our CBA, at what level of vision they become ET. Good for intermittent types of ET to do this. Same for XT’s.

25
Q

What is Monocular Occlusion used for?

A

To differentiate true & simulated convergence excess esotropia.
Those with true convergence excess exhibit a manifest convergent strabismus when viewing a close object and a small, well-controlled latent strabismus upon fixation of a distant object. Those with simulated convergence excess have a comparable near deviation to those with true convergence excess but can be shown to have a distance deviation that approaches the size of the near strabismus once the normal fusional mechanisms are disrupted by a period of prism adaptation.

26
Q

How is Monocular Occlusion conducted?

A
  • Patient wears occlusion for 30 - 60 minutes
  • Alternate PCT measurements are retaken without allowing the patient to regain fusion
  • Assess for increase in distance angle which may match the near angle

Cover one eye and see if the angle changes when able to fuse or not (when uncovering the eye). Tells us max angle of deviation, will tell us if there is a hidden deviation angle where the patient is controlling it by fusing so would want surgery on this higher amount compared to their PCT normal response.

E.g. Nr 40 and Dist 20. Do this Monocular Occlusion to see if the Dist angle increases (if it does this is a simulated ET)

27
Q

What are the potential results of Monocular Occlusion / PAT?

A

True Convergence Excess -
No significant increase in distance deviation following monocular occlusion or prism adaptation

Simulated Convergence Excess -
Significant increase in distance deviation following monocular occlusion or prism adaptation

28
Q

What should you check for in late-onset ET (Acute-onset ET or normo-sensorial ET)?

A
  • Visual acuities – is there any explained visual loss
  • Previous history of esophoria or microtropia (i.e. broken down/decompensation into a ET)
  • Refraction – underlying myopia or hypermetropia?
  • OM – for lateral rectus function
  • Lids
  • Pupils
  • Concomitant esotropia can occur following occlusion or visual loss, due to a decompensation of an esophoria or microtropia, for an unknown reason, or due to myopia

Occurs between the ages of 2 - 5yo

29
Q

How do you do the 10PD test for amblyopia?

A

Fixation-preference testing has been useful in detecting amblyopia in children unable to give reliable visual acuities, except for children with small-angle tropias and those without manifest deviations.

This test is performed by placing a vertically oriented 10 PD prism over one eye, either base down or base up (more commonly base down). The vertical prism induces a hypertropia, allowing evaluation of fixation preference. Strong fixation preference for one eye is indicative of amblyopia. Amblyopia can be bilateral in children with bilateral blurred retinal images (e.g., bilateral congenital cataracts, or bilateral high hypermetropia >+5.00 sphere)

The fixation preference test is based on the assumption that nonamblyopic strabismic patients will alternate fixation or hold fixation well with either eye during binocular viewing. Conversely, amblyopic patients will show strong fixation preference with the sound eye and will not hold fixation with the amblyopic eye.

30
Q

Differential Diagnosis & Investigation:

4yo

Rx
R: +4.50DS
L: +4.75DS

CT
Cgls N: small esophoria with good rec
Cgls D: NAD
Sgls N+D: moderate right esotropia

PCT
Cgls N: 6PD BO
Sgls N+D: 35PD BO

A

Same prescription in both eyes

Without glasses Mod RET
With glasses controlled to E at Nr and NAD at Dist

PCT said without glasses is same at Nr and Dist at 35PD BO but with glasses down to 6PD

4yo = no surgeryIntermittent fully accom ET as completely controlled with glasses. Require prescription full-time due to size of deviation.

= Fully accommodative esotropia. You would want to carry out a full investigation of BSV, including sensory, motor and stereopsis. You would want to check that this patient was not corrected to a microtropia. You would also want to know their visual acuities

31
Q

Differential Diagnosis & Investigation:

Age 6 months old

VA unaided Cardiff Cards
R: 0.200
L: 0.500

CT
Sgls N: marked left esotropia with good fixation
Sgls D: moderate left esotropia with good fixation

PCT
Sgls N: 50PD BO
Sgls D: 35PD BO

A

Slightly reduced VA in LE so potentially amblyopic

Without glasses marked LET at Nr and moderate LET at Dist

PCT without glasses 50PD BO at Nr & 35PD BO at Dist

= Constant ET potentially but need to prescribe glasses to ensure no accommodative element. Provide cycloplegic refraction and reassess the patient with prescription if needed. Could be early-onset due to 6mo. Unlikely to be infantile ET due to alternation not changing.

32
Q

Differential Diagnosis & Investigation:

Age6 years old
Rx
R: +3.75DS
L: +3.75DS

VANot yet tested

CT
Cgls light: moderate esophoria with delayed rec
Cgls N: initially straight à moderate right esotropia with good rec
Cgls D: small esophoria with good rec
Sgls N+D: moderate right esotropia

PCT
Cgls N:20PD BO
Cgls D: 6PD BO
Sgls N+D: 35PD BO

A

Still in critical period

Same prescription in both eyes

CT without glasses is a moderate RET at Nr and Dist
CT with glasses Mod RET at Nr but controlled to E at Dist = Convergence Excess

PCT without glasses Nr and Dist is 35PD BO
With glasses at nr 20PD (so sort controlled but not fully) and controlled to 6PD at dist

= Convergence excess ETYou would want to perform an appropriate VA test for the patient e.g. letter test (may need matching card). You would want to discuss full investigation of BSV, PAT and AC/A ratio to confirm your diagnosis of Convergence exceess esotropia.

33
Q

Differential Diagnosis & Investigation:
Age10 years

Rx(nil given)
R: +1.75DS
L: +1.50DS

VAunaided logmar
R: 0.120
L: 0.060

CT
Sgls N+D: marked right esotropia with poor fixation

PCT
Sgls N+D: 55PD BO

BagoliniRight suppression response

AC/A ratio: 4:1

A

10 years old so outside of the critical period

Low prescription that’s not in use currently VA not significantly different in each eye

CT without glasses showed a marked RET for Nr and Dist at 55PD BO

AC/A is normal range so not likely a convergence excess ET or partially accom constant ET

Right suppression response is interesting as vision not significantly different in each eye.

= Constant ET without accommodative element

34
Q

Example recording of a PODT:

A

PODT cgls (fixing a target)

1/3m no complain of diplopia up to 20 dioptres over- and under-correction

6m no complain of diplopia from 20 dioptres under-correction to 10 dioptres over-correction, complain ofdiplopia from 10 to 20 dioptres over-correction

Strabismus 106 (35 decks)

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