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Strabismus 106 > Heterophoria > Flashcards

Heterophoria Flashcards

1
Q

What is the definition of Heterophoria?

A

Both visual axes are directed towards the fixation point but deviate on dissociation

Latent deviation = detected on Alternate Cover Test

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2
Q

What’s Orthophoria and how is it reported?

A

No heterophoria i.e. orthophoric
Reported as NAD which is ‘No Abnormality Detected’

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3
Q

What’s the most common type of heterophoria?

A

Exophoria is more common than esophoria and vertical are the most uncommon and suggestive of vertical muscle imbalance

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4
Q

What is Cyclophoria?

A

A form of heterophoria, a rotation of the globe on dissociation (excyclophoria and incyclophoria)

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5
Q

What do we report on in a CT for a heterophoria?

A

1) Size
2) Direction
3) Control
4) Recovery
5) Diplopia

i.e. Initially straight on dissociation but becomes mod R ET with diplopia prior to slow recovery with effort

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6
Q

When an X is equal at Nr & Dist, what’s it also known as?

A

Non-Specific

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7
Q

When an X is bigger at Nr than Dist, what’s it also known as?

A

Convergence Weakness

It’s a convergence weakness as the eye is drifting outwards MORE at near when it should be moving inwards for convergence

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8
Q

When an X is smaller at Nr than Dist, what’s it also known as?

A

Divergence Excess

In divergence excess exophoria to find out if an exotropia is present you need to increase the fixation distance beyond 6m

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9
Q

In an E, what is it called when Nr & Dist are equal?

A

Non-specific

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10
Q

In an E, what is it called when bigger at Nr than Dist?

A

Convergence Excess

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11
Q

In an E, what is it called when it’s smaller at Nr than Dist?

A

Divergence Weakness

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12
Q

What does a well controlled / compensated heterophoria look like?

A

Well-Controlled Phoria

Rapid Recovery

Sufficient Fusional Reserves (normal)

Maintain comfortable BSV

Symptom Free

Good Nr point on Conv and Control

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13
Q

What is a poorly controlled / decompensated heterophoria?

A

Intermittent Manifest Strabismus

Slow Recovery

Insufficient Fusional Reserves (Reduced)

Tenuous BSV

Symptoms of Diplopia & Asthenopia

Poor Function of Convergence

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14
Q

What is Tenuous BSV?

A

E.g. may see Worth Lights as 2, 4 or 5 at different moments in time

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15
Q

What is Asthenopia?

A

The technical name for eye strain or fatigue. Often causes headaches that are frontal caused by the effort to maintain BSV

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16
Q

How do we investigate a heterophoria?

A

Orthoptic
Detection – cover test

Assessment of control – cover test, fusion, CBA, stereoacuity, observations

Symptoms – patient complaints

Measurements – PCT (concomitance / incomitance)

Ophthalmic
Refraction, fundus and media assessment

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17
Q

What’s a concomitant or incomitant deviation?

A

Concomitant =
Same size of deviation (angle of deviation) in all positions of gaze

Incomitant =
Different angle of deviation at different positions of gaze which is complicated when preparing for surgery as having to know what angle is best to correct

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18
Q

Why is PFR important in heterophoria?

A

The opposite fusion range compensates for the deviation (controls the deviation)

Esophoria = BI fusion range (negative fusional reserve)

Exophoria = BO fusion range (positive fusional reserve)

Important features =
Range of fusion
Break point
Recovery point
Appreciation of diplopia / suppression

Heterophoria is often described as ‘compensated’ or ‘well compensated’ when the motor fusion amplitude is sufficient to maintain comfortable motor fusion and the patient is symptom free. If fusion is insufficient = decompensates

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19
Q

What do we mean when we say a heterophoria need “reserves” for PFR?

Does this person have enough?

PCT gls
Nr 18 BO E
Dist 18 BO E

PFR gls
Nr 2BI – 30BO c/diplopia
Dist 2BI – 30BO c/diplopia

A

This means that they’re controlling for an 18 EsoPHORIA (E, PCT) plus the 2BI from their PFR at Nr for a total of 20BI at Nr. This however means they only have 2BI “in reserve” so have a high chance of decompensating and/or diplopia so the aim would be to improve BI range via orthoptic exercises. Would check for both Nr & Dist.

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20
Q

If someone with a heterophoria gets convergence fatigue, what does this mean for them?

A

If they experience convergence fatigue then they’re likely to get diplopia, asthenopia or decompensation

21
Q

What further investigations do we need to consider in heterophoria relating to symptoms?

A

1) Diagnostic Prims
2) Diagnostic Occlusion

22
Q

How are Diagnostic Prisms used in Heterophoria?

A

Similar to PAT

Use Fresnel prisms on patients glasses to ‘compensate’ the heterophoria, significantly reduce or fully correct with prisms and ask them to wear for 2 weeks.

If the symptoms improve in the 2 weeks then we know the symptoms are caused by the heterophoria and helps determine the level of control at the corrected angle

23
Q

How is Diagnostic Occlusion used in Heterophoria?

A

Used in latent deviations that are bigger at Nr or at Dist
Used in Intermittent X or E’s

Ask the patient to wear a patch to cover one eye full-time for at least 24 hours.

If the symptoms improve during the period being monocular then the symptoms were caused by the binocular heterophoria. Retake measurements on the visit.

24
Q

How do we assess compensation of heterophoria?

A
  • Speed of recovery to BSV after dissociation i.e. during CT
  • Near point convergence
  • Extent of fusion amplitude

Adults are usually symptomatic whereas children develop suppression/are symptom free

25
Q

What are the 3 overarching factors that cause decompensation of a latent deviation?

A

1) Optical
2) Medical
3) Other

26
Q

What Optical Factors cause decompensation of a latent deviation?

A
  • Uncorrected / Under-corrected Refractive Error
  • Incorrect Refractive Errors / Prismatic Correction
  • Poorly Fitting Glasses
  • Aniseikonia (image size/shape)
27
Q

How can uncorrected refractive error (optical factor) lead to decompensation of a latent deviation?

A

This can be a planned undercorrection or the patient may be refusing to wear their glasses. This disturbs the normal accommodative: convergence relationship

  • Hypermetropia = eso’s
  • Myopia = exo’s
28
Q

How can incorrect refractive error or prismatic correction (optical factor) lead to decompensation of a latent deviation?

A

Can dissociate the eyes if one eye is reduced more than another

29
Q

How can poorly fitting glasses (optical factor) lead to decompensation of a latent deviation?

A
  • Poor VA (as not looking through the optical centre of the lens)
  • Prismatic effect can occur if the lenses are decentred, making control more difficult if the patient then has a larger deviation to control or if the glasses are tilted or wonky which can cause a vertical prismatic effect which can make achieving BSV difficult (as only a small vertical deviation can cause many issues as our vertical PFR is small compared to horizontal)
30
Q

How can Aniseikonia (image size/shape; optical factor) cause decompensation of a latent deviation?

A

Can occur in anisometropia. This is a difference in size and/or shape of the retinal images of the 2 eyes which can be very difficult to fuse. Can often be reduced by CL correction

31
Q

What Medical factors can cause decompensation of a latent deviation?

A
  • General Health
  • Medication
  • Head Injury
    Central fusion disruption & Accommodation
  • Alcohol
32
Q

What other factors (not optical or medical) can cause decompensation of a latent deviation?

A
  • Visual Demand (Binocular or Monocular Viewing Conditions)
  • Occlusion
33
Q

What are the aims of managing/treating a heterophoria?

A
  • Improve control of heterophoria
  • Relieve symptoms
    Sometimes a poorly controlled heterophoria is treated in an asymptomatic child to prevent later decompensation to a manifest strabismus. As part of the investigation GH must be asked to see if unstable or variable, then any treatment for heterophoria may not tackle the underlying GH problem. All patients have to have a fundus and refraction check and refraction must be following cycloplegia in children to ensure accurate results.
  • Prevent risk of decompensation
  • Reduce factors for causing decompensation
34
Q

What do we do to manage/treat a heterophoria? and When?

A

When =
- Non-symptomatic but risk of decompensation

  • Child at risk of suppression & strabismic amblyopia

How? =
- Increasing fusion amplitude

  • Reducing the size of the heterophoria
  • Fundus check & refraction
  • Glasses wear. Cooperative & willing!

Conservative Options =
- Orthoptic Exercises
- Optical Correction
- Prisms

Invasive Options =
- BT
- Surgery

35
Q

When do we use Orthoptic Exercises for managing a heterophoria?

A
  • When they’re suitable for treatment (age, cooperation, motivation, small angles and strabismus of <18PD)
  • For improving fusional amplitude
    (Positive in X BO,
    Negative in E BI)
  • For improving relative convergence
    (Near Stereograms in X, Distance Stereograms in E)
36
Q

How do we use Prisms in treatment of heterophoria?

A
  • Reduce amount of heterophoria to control
    (ideally give the lowest strength to control and have BSV which is often chosen by the patient)
  • Fresnel prisms must be stable for >6mo to be incorporated
37
Q

When do we use Prisms in treatment of heterophoria?

A
  • Elderly
  • Smaller heterophoria who have either to respond to orthoptic exercises or have failed to maintain improvement from exercises long-term. It’s difficult to control prisms as when prisms for a phoria you have to ensure they’re not dependent on them as they may continue to “eat up” the prism if they’re not also trying exercises or time without them.
  • Those with a vertical heterophoria
  • Those with post-op consecutive heterophoria during the early post-op period
38
Q

What are the advantages of using prisms in heterophoria treatment?

A
  • Elderly patient
  • Temporary and long-term relief of diplopia
  • Variable diplopia
  • Vertical phorias
  • Small deviations not suitable for surgery/BT
  • Could be used intermittently for extra control
  • Failed orthoptic exercises or surgery
  • Post-operatively
39
Q

What are the disadvantages of using Prisms in the treatment/management of heterophorias?

A
  • Expensive
  • Heavy & thick glasses
  • Only up to 15-20PD
  • Diplopia without glasses
  • Can’t wear contact lenses
40
Q

When are BT injections useful in the treatment/management of heterophorias?

A

Useful if:
- Unsuitable for surgery

  • Small decompensating heterophoria
  • Significant consecutive heterophoria
  • Unsatisfactory long term use of prisms

Often results in a decrease in the size of the heterophoria and better overall control

41
Q

When is surgery suitable for the treatment/management of a heterophoria?

A

Suitability:
- Large heterophoria

  • Unsuccessful/unwilling to have results from other non-surgical treatments
  • Depends on size of deviation at Nr & Dist
  • Consider position with largest deviation
  • Adjustable sutures can be used to refine the initial post-surgical eye position
  • Those with an incomitant heterophoria (aim to restore concomitance and relieve symptoms by reducing the size of the deviation)
42
Q

What is it called when an X is the same at near and distance? What type of surgery would it suggest?

A

Non-specific
LR recess / MR resect

43
Q

What is it called when an E is the same at near and distance? What type of surgery would it suggest?

A

Non-specific
MR recess / LR resect

44
Q

What is it called when an X is the bigger at near than distance? What type of surgery would it suggest?

A

Convergence weakness
Bimedial resect
LR recess < MR resect

45
Q

What is it called when an E is the bigger at near than distance? What type of surgery would it suggest?

A

Convergence excess
Bimedial recess

46
Q

What is it called when an X is the smaller at near than distance? What type of surgery would it suggest?

A

Divergence excess
Bilateral recess

47
Q

What is it called when an E is the smaller at near than distance? What type of surgery would it suggest?

A

Divergence weakness
Bilateral resect OR
MR recess < LR resect

48
Q

What are the post-op management options in a heterophoria?

A

Want to maintain long-term control of heterophoria

May require ongoing treatment and management

Patient may be able to self-manage symptoms

Strabismus 106 (35 decks)

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