Infantile Esotropia

Question 1

What are the clinical characteristics of Infantile ET?

Answer 1

• Onset is between birth and 6mo
• Large >30PD
• Stable angle (doesn’t change with
  fixation distance)
• Initially alternation with crossed
  fixation
• Potential for normal BSV limited
• No sig. refractive error
• Essential infantile ET has a normal CNS

Previously called congenital but now it’s not always congenital

Question 2

What might Infantile ET be associated with?

Answer 2

• Latent or manifest latent nystagmus
• Apparent defective abduction (this
  can become a true defect in
  abduction if left untreated)
• Dysfunction of oblique muscles
• Asymmetric Optokinetic
  Nystagmus (OKN)
• Dissociated Vertical Deviation
  (DVD)
• Alphabet Patterns

Question 3

Why does it sometimes look like infants have a double ET which is impossible?

Answer 3

Because of cross fixation of free association. Turn their head toward the fixing eye; looks like both eyes are inwards as the fixing eye moves towards the nose if turning head toward the fixing eye

Question 4

What is the aetiology of infantile ET?

Answer 4

It’s unknown;
- Hereditary factors (may not be just strabismus but poor fusion or binocular functions)

• Multi-Factorial
• Deficient or delayed development of motor fusion
• Could be related to sensitivity to targets moving way from the infant (so a difficulty relaxing the eyes to diverge)

Question 5

How does onset affect investigations of infantile ET?

Answer 5

Due to instability of the eye position at 0-6mo it makes accuracy of determining age of onset difficult but this can affect prognosis. Will see by 4mo if the ET resolve on its own.

Question 6

What does the angle of deviation look like in infantile ET?

Answer 6

• Large
• No sig. difference in Nr and Dist
• +ve lenses make little difference
• Common to have an associated
  vertical deviation

Question 7

What nystagmus is related to Infantile ET?

Answer 7

Manifest Latent Nystagmus (MLN)

Question 7

How is amblyopia associated with infantile ET?

Answer 7

• Gross amblyopia is unusual due to alternation
• Mild to moderate in 35 - 41% cases
• Much less if untreated (Calcutt).
  More common post-op as when
  improving alignment they can end
  up favouring one eye and end up
  amblyopic

Question 7

How are associated vertical deviations involved in Infantile ET?

Answer 7

• Superior Oblique (SO) under-actions & V-patterns
• High incidence of DVD (dissociated vertical deviation)

Question 8

What is Asymmetric Optokinetic Nystagmus (OKN)?

Answer 8

The “train” nystagmus. It’s a rhythmic movement. Can feel the eyes doing this reflexive movement. In Asymmetric OKN they have a lower gain (slow-phase eye velocity/stimulus velocity) for monocular temporalward than nasalward visual field motion.

Question 9

How is Asymmetric Optokinetic Nystagmus (OKN) involved in infantile ET?

Answer 9

• Have an abnormal nasal to temporal response.
• May lack evidence of BSV
• May have abnormal motion processing whereby the Visual cortex fails to transmit temporally directed motion to nucleus of optic tract. Also present in normal infants < 3/12 & other forms of strabismus & relatives
• Relationship with latent nystagmus (be vigilant of this in infants as it’s hard to spot due to lack of fixation)
• Predictor of DVD (Dissociated Vertical Deviation)

Question 10

How is abnormal head posture (AHP) related to infantile ET?

Answer 10

• Turn their face to the fixing eye, especially if nystagmus is present
• Head tilt to fixing eye but tilt more common with DVD (Dissociated Vertical Deviation) but then more often to non-fixing eye.

Question 11

What ocular movements are associated with infantile ET?

Answer 11

• Cross fixation is a “lazy” way of looking to the side by changing fixation i.e. RE to look left gaze and LE to look right gaze which gives them the impression of an apparent defective abduction (cross-fixation) if actually present, most likely due to MR contracture.
• Can test with the Doll’s Head & with occlusion. Cover one eye and then move their head to see if the eyes abduct with this movement
• Dysfunction of obliques possible such as IO over-action (o/a) and SO (u/a) underaction (need to ensure not a congenital SO palsy)
• Atropic muscle pulleys can cause upshoots or downshoots of the eyes

Question 12

How do we assess binocular function in infantile ET?

Answer 12

Rarely demonstrable pre-op due to the difficulty testing at this age (synoptophore or PAT). Whilst BSV has been shown to occur post-op it’s not a good level that’s expected.

Question 13

What’s the aim of the management in infantile ET?

Answer 13

To achieve equal visual acuity (as alternating at present would leave them untreated for the strabismus), attain a good alignment and ideally gain some form of binocular co-operation

Question 14

How do we treat infantile ET with an angle >35PD?

Answer 14

Surgery

Question 15

How do we treat infantile ET with an angle equal to or less than 35PD when it’s a stable angle?

Answer 15

BT / Surgery

Question 16

How do we treat infantile ET with an angle equal to or less than 35PD when it’s a variable angle?

Answer 16

Age 8 - 12mo = Observe or BT

Age > 8 - 12mo = Surgery or BT

Question 17

How do we treat an infantile ET in an under 8mo with an angle <40PD?

Answer 17

Observe;
Spontaneous resolution has been reported in 27% of cases but these were predominantly in those that were referred early; had an angle less than 40∆ which was intermittent or variable on presentation. (PEDIG 2002)

Question 18

Should we order refractive treatment in infantile ET?

Answer 18

Most are emmetropic due to the alternating nature of the strabismus BUT if ordering would use +2.50 or above but if not making a difference to VA or the strabismus then the trial should be ended.

Question 19

When should we treat any amblyopia in infantile ET?

Answer 19

Fixation pattern helps monitor progress

Limitations of preferential looking

Risk of occlusion amblyopia

Question 20

Should we use alternate occlusion in Infantile ET?

Answer 20

Jamplsky (1978) considered whether the alternation was the issue so suggested alternate occlusion with them never using both eyes together

Question 21

At what age in infantile ET are they more likely to achieve some form of BSV?

Answer 21

Before 2 years old (European early vs late infantile strabismus surgery survey) but more accurate measurements are done after 2 years.

Question 22

How do we do surgery in infantile ET?

Answer 22

• Bimedial MR recessions with/ without conj recessions (25-45∆)
• Bimedial MR recession and single LR resection (50-65∆)
• Combine with BT to both MR if >70∆

Becoming more common is BT and surgery into MR. More evasive however in babies as would need to give them anaesthetic for BT so some argument that you might as well do surgery at this point.

Question 23

What is a conjunctiva recession?

Answer 23

Conjunctiva recession – reduces mechanical restrictions, particularly if the strabismus was there for a long time

Question 24

How is Botox (BT / Botulinum Toxin) used in the management of Infantile ET?

Answer 24

• Results found BT less effective than surgery in esotropias >35∆ but comparable to surgery in those <30∆ Although up to 3 injections could be required
• For angles >65∆ success has been shown by combining BT to one or both MR and bilateral MR recessions

Question 25

What type of ET is Infantile ET?

Answer 25

Constant ET