Strabismus

Question 1

What is a squint?

Answer 1

• misalignment of the eyes
• also known as strabismus
• when the eyes aren’t aligned, the images on the retina don’t match and the person will experience double vision

Also known as strabismus. When the eyes aren’t aligned, the images on the retina don’t match and the person will experience double vision.

Question 2

What is a lazy eye and its actual name?

Answer 2

• when this occurs in childhood, before the eyes have fully established their connections with the brain, the brain will cope with this misalignment by reducing the signal from the less dominant eye
• this results in one eye they use to see (the dominant eye) and one eye they ignore (the lazy eye)
• if it’s not treated over time, the ‘lazy eye’ becomes progressively disconnected from the brain and over time the problem becomes worse
• this is known as amblyopia

Question 3

What are concomitant squints?

Answer 3

These are due to difference in the control of the extra ocular muscles.

The severity of the squint can vary.

Question 4

What are paralytic squints?

Answer 4

Rare.

Due to paralysis in one or more of the extra ocular muscles.

Question 5

What do strabismus and amblyopia mean?

Answer 5

Strabismus = the eyes are misaligned.

Amblyopia = the affected eye becomes passive and has reduced function compared to the other eye.

Question 6

What do esotropia and exotropia mean?

Answer 6

Esotropia = inward positioned squint (affected eye towards the nose).

Exotropia = outward positioned squint (affected eye towards the ear).

Question 7

What do hypertropia and hypotropia mean?

Answer 7

Hypertropia = upward moving affected eye.

Hypotropia = downward moving affected eye.

Question 8

What are some causes of a squint?

Answer 8

In an otherwise healthy child, the cause is usually idiopathic.

Other causes include hydrocephalus, cerebral palsy, SOLs (e.g., retinoblastoma), and trauma.

Question 9

What is looked at on examination?

Answer 9

General inspection, eye movements, fundoscopy (or red reflex) to rule out retinoblastoma, cataracts and other retinal pathology, and visual acuity.

Question 10

What is the Hirschberg’s test?

Answer 10

Shining a pen torch at the patient from 1 meter away.
- When they look at it, observe the reflection of the light source on their cornea.
- The reflection should be central and symmetrical.
- Deviation from the centre will indicate a squint.

When they look at it, observe the reflection of the light source on their cornea. The reflection should be central and symmetrical. Deviation from the centre will indicate a squint.

Question 11

What is the cover test?

Answer 11

• Cover one eye and ask the patient to focus on an object in front of them.
• Move the cover across to the opposite eye and watch the movement of the previously covered eye.
• If this eye moves inwards, it has drifted outwards when covered (exotropia) and if it moves outwards it means it has drifted inwards when covered (esotropia).

Question 12

When does treatment need to be started?

Answer 12

Up until the age of 8, the visual fields are still developing, therefore treatment needs to start before 8 years.

Delaying treatment increases the risk of the squint becoming permanent.

Question 13

What is the management for a squint?

Answer 13

• An occlusive patch can be used to cover the good eye and force the weaker eye to develop.
• Alternatives may involve using atropine drops in the good eye, causing vision in that eye to be blurred.
• An ophthalmologist coordinates the management.
• It is important to treat any underlying pathology (e.g., cataracts) and refractive errors can be corrected with corrective lenses.