Opthalmology - Squint

Question 1

Definition

Answer 1

• Also known as strabismus = this is misalignment of the eyes
• When the eyes are not aligned, the images on the retina will not match and the patient will experience double vision

Question 2

Pathophysiology

Answer 2

• In childhood, as the eyes have not fully established their connections with the brain, the brain copes with this by reducing the signal from the less dominant eyes.
• This results in one dominant eye and one eye which will be ignored (lazy eye)
• When left untreated, this lazy eye becomes more and more disconnected from the
  brain and the problem worses - this is known as amblyopia
• Concomitant squints are due to differences in the control of the extra ocular muscles. The severity of the squint can vary.
• Paralytic squints are rare. They are due to paralysis in one or more of the extra ocular muscles.

Question 3

Different types of squint

Answer 3

1. Amblyopia - the affected eye becomes passive and has reduced function compared to the other dominant eye
2. Esotropia - inward position squint -> affected eye deviated towards the nose
3. Exotropia - outward position quint -> affected eye deviated towards the ear
4. Hypertropia - upward moving affected eye
5. Hypotropia - downward moving affected eye

Question 4

Aetiology

Answer 4

• Idiopathic
• Hydrocephalus
• Cerebral palsy
• Space occupying lesion e.g retinoblastoma
• Trauma

Question 5

Diagnosis

Answer 5

• Eye movements and inspection
• Fundoscopy
• Visual acuity
• Hirschberg’s test: shine a pen torch at the patient from 1 metre away, when they look at it, observe the reflection of the light source on their cornea - this should be central and symmetrical.
• Cover test: cover one eye and ask the patient to focus on an object in front of them.
  Move the cover to the opposite eye and watch the movement of the other eye and observe for any exo/esotropia.

Question 6

Management

Answer 6

• Treatment must start before 8 years of age
• Occlusive patch can be used to cover the good eye and force the weak eye to develop
• Atropine drops can be used in the good eye causing blurry vision and again forcing the bad eye to develop.
• Corrective lenses -> ophthalmologist