Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Strabismus 106 > Intermittent XT > Flashcards

Intermittent XT Flashcards

1
Q

What are the aetiologies of intermittent XT?

A

Innervation Factors -
Imbalance of convergence & divergence for classification

Hereditary factors are also shown to influence the prevalence. However, in the majority of these genetic studies exotropia and esotropia have been included so it is unclear whether different subtypes have different inheritance models. Sub-analysis of this group would appear that there are possible differences.

In the presence of neurological abnormalities and the deviation of an IXT at near exceeds distance by 10PD 66% have associated neurological abnormalities.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What did Von Noorden find out about the natural progression of Intermittent XT? & how did Burian define this?

A

Von Noorden undertook a study to observe the natural progression of IXT in 51 subjects. He noted that in the majority (75%) progression of the deviation occur, however, there were a minority who didn’t change (9%) and in 16% there was actually improvement.

Burian explained this difference by segregating groups into the type. By doing so believed that those with distance exotropia who were true type – remained stable, whereas those with simulated exotropia, near exotropia or non-specific/basic types progressed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What did Burian find out about the stability for Distance XT’s?

A
  • Distance exotropia of true type remain stable,
  • Distance exotropia of simulated type progress to decompensate for near
  • Near exotropia rapid progression to symptomatic and constant deviation
  • Non-specific/ basic type progress to larger size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is distance XT also known as?

A

Divergence Excess XT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is a Distance XT defined?

A

Fusion at Nr (often latent and can be large depending on ability to control) and distance XT (>10PD difference between Nr & Dist)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When do Distance XT’s occur?

A

Distance exotropia has onset by approximately 12 month/1 year of age although has been reported to occur later.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are symptoms of a Distance XT?

A

Symptoms:
- Typically none
- Diplopia – rare
- Panoramic vision
- Photophobia
- Asthenopia (eye strain/fatigue)
- Diplophotophobia: May close one eye in bright sunlight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do we investigate a Distance XT?

A

Fundus and media
Refraction
History
Visual acuity
Cover test
Ocular movements
Convergence
Assess control of deviation
Measurement of deviation
Diagnose true / simulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What ocular movements do we need to be aware of in a distance XT?

A
  • Need to carefully check adduction
  • A or V patterns more likely (V is often an over-action of the IO)
  • Lateral incomitance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do we test for control in an intermittent Nr XT deviation?

A
  • Cover test
  • Near point of convergence (good for Nr deviations)
  • Motor fusion
  • CBA (Read down chart to see when they become manifest; doesn’t necessarily have to be at the point their VA is)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do we assess control using CBA?

A

1) Accommodation
Accommodative Convergence (AC/A)

2) Fusional Convergence
Convergence Accommodation

The consequences of this are blur, asthenopic symptoms, problems with school work/avoiding detailed work

Need to improve positive relative vergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is control like in a distance XT?

A

Exo deviation control varies over a day, and over an examination in most children with intermittent XT.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do we test stereoacuity in an intermittent distance XT?

A

1) FD2
2) Distance Randot Stereotest

Holmes et al 2007 - FD2 stimulates fusion in intermittent XT even when control poor. New distance Randot test very sensitive to disturbances of binocularity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If someone has smaller XT on the sides (laterally) during PODT then what is this called?

A

Lateral incomitance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What in a distance XT causes a risk of over-correction?

A

Lateral incomitance have a higher risk of overcorrection (to a consecutive ET) and homonymous diplopia on lateroversions

BUT
Variability as to whether this truly exists. Induce some artifacts of the prisms if not held in the correct position. If higher on side-gaze = higher risk of over-correction during surgery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the types of Intermittent XT?

A

Distance XT (True or Simulated)

Near XT

Non-Specific XT (Basic XT)

17
Q

What will a True Distance XT look like?

A
  • XT on distance
  • Fixation with BSV on Nr
  • Fixation under all testing conditions
18
Q

What does Simulated Distance XT look like?

A

The Nr angle of deviation INCREASES with either:

1) Prolonged disruption of fusion (i.e. patching) - 30-60mins of disruption without letting them fuse again

2) Elimination of accommodation (high AC/A ratio = simulated due to accom; assess near angle with +3.00DS)

19
Q

What did Kushner find out about simulated XT?

A

340 patients with exotropia. 154 were found to have a high AC:A ratio prior to occlusion. After occlusion only 22 patients had a high AC:A ratio and the remainder had pseudo high AC:A. The presence of high AC:A is infrequent in patient with XT but is highly predictive of a post op ET at near.

BUT some think this isn’t real as other studies have shown no difference

20
Q

What does True Distance XT look like in terms of AC/A and Occlusion?

A

AC/A - Normal
Occlusion - No Change

21
Q

What does Simulated Fusion Distance XT look like in terms of AC/A and Occlusion?

A

AC/A - Normal
Occlusion - Increases Nr Angle

22
Q

What does Simulated Accommodative Distance XT look like in terms of AC/A and Occlusion?

A

AC/A - High
Simulated Accommodation - No Change

23
Q

What did Buck et al (2012) find out about XT management?

A

The findings of the present study highlight that:
a) Many children with X(T) do not experience adverse outcomes from observation or non-surgical treatment;

b) The risk of conversion from intermittent to constant exotropia is minimal;

c) A significant proportion of children who undergo surgery for X(T) experience an overcorrection, occasionally with loss of near stereoacuity.

24
Q

What’s the Newcastle control score?

A

In 2004, Haggerty et al devised a scoring chart that incorporated control observed at home and control found in clinic to determine whether further intervention would be required. In 2007, Buck et al, obtained data on 272 children with IXT and followed up 157 of them. They noted that a high (poor) NCS (≥4) predicted surgery would be required.

25
Q

What is the PEDIG (Office) Control Score?

A

Looks at control of deviation at near and distance with a score between 0 and 5

26
Q

What is the LACTOSE grading scale?

A

Canadian Group
Easy system for deciding whether someone has good or poor control at near and distance by their results on the cover test. Predicts very well the outcome of surgery.

Lactose 0 - 4

27
Q

When do we use Orthoptic Exercises in distance XT? How?

A
  • To improve control for near
  • Pre-operative
  • Post-operative

We eliminate suppression, join diplopia or exercise positive relative convergence

28
Q

What is the optical treatment for distance XT?

A

Minus lenses
Wearing glasses full-time, have additional minus power over the cyclo prescription with the aim to control and/or reduce the angle of deviation

Found best for those with an equal to, or less than, 4 NCS score

Aim is to reduce them out of the minus lenses with exercises etc as long-term the eye will return to its original position as lacking the control otherwise

29
Q

How should we use Prisms as a treatment for distance XT?

A
  • Minimum BI prism to restore BSV for distance fixation
  • Fresnel prism or incorporate into glasses
  • Gradually reduce strength
  • With orthoptic exercises

Fresnel prisms may be less tolerated in children as they decrease VA and contrast sensitivity and dynamic VA

BUT
Pilot study by Summers et al (2023) – RCT prisms vs no prisms 57 children, revealed no benefit to warrant a further larger trial – suggests that prisms don’t help with deviations long-term

30
Q

Why would we do occlusion therapy in a distance XT?

A

NOT FOR AMBLYOPIA TREATMENT: this is management for CONTROL not VA

6hrs daily for 4-6wks and if angle is reduced then reduce occlusion, if there’s no change in angle then increase occlusion to FTTO

There is evidence it’s more successful if treatment commenced soon after onset and that there are better surgical results achieved post-op

31
Q

When we’re considering surgery if conventional treatments have not worked, what must we consider in distance XT?

A

Age (early/delayed)

Type (true/simulated, A or V pattern)

Amount (size of dev, lateral incomitance)

Aim (under/over-correct)

32
Q

What type of surgery do we do in True Distance XT?

A

Bilateral Rectus Recession (some evidence for recess/resect too)

33
Q

What type of surgery do we do in Simulated Fusional Distance XT?

A

Lateral Rectus Recession
&
Medial Rectus Resection

34
Q

What type of surgery do we do in Simulated High AC/A Distance XT?

A

Bilateral Recession

35
Q

How do we determine the amount of surgery in a distance XT?

A

Size of deviation must be considered alongside lateral incomitance as if they have lateral incomitance then we need to reduce the amount of recession we do in mm as they’re at a higher risk of being overcorrected

36
Q

What is Nr XT?

A

XT for Nr fixation & BSV for distance fixation

Nr angle at least 10PD larger than the distance angle

37
Q

What is Non-Specific (Basic) XT?

A

Intermittent XT for Nr & Dist fixation less than 10PD difference or equal at both

38
Q

What can cause a Nr XT?

A
  • Convergence palsy
  • Primary convergence insufficiency
  • Accommodative insufficiency
  • Neurological disease

Need to differentiate near XT from other conditions

39
Q

How can we treat Nr & Non-Specific XT?

A
  • Orthoptic Exercises
    small angles <20PD
  • Optical treatment
    Prisms
    Lenses
  • Surgery
    Near Exotropia - Medial recti resections / MR resection & LR recession (larger resections than recessions)
    Non-specific - Medial rectus resection and Lateral rectus recession

Strabismus 106 (35 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions