Pseudo-Strabismus

Question 1

What is a pseudo-strabismus?

Answer 1

The clinical impression of a manifest ocular deviation when no squint is present

Question 2

What are the main possible causes of a pseudo-strabismus?

Answer 2

Facial asymmetry (receding brow makes eyes appear inward, prominent cheekbone makes eyes appear outward, angle kappa), IPD, Wide Nasal Bridge or Prominent Epicanthal Folds

Question 3

How does a wide nasal bridge make it look like someone has a pseudo-strabismus?

Answer 3

Because the inner corner of the eye (medial canthus) is further away from the nose than the outer corner (lateral canthus)

Question 4

What are epicanthal folds?

Answer 4

Small folds of skin that cover the inner corner of the eye (medial canthus).

Question 5

How is the severity of epicanthal folds seen?

Answer 5

Based on the degree of caruncle obstruction which correlates to how much we think there’s a deviation of the eyes

Question 6

Who are severe epicanthus folds more common in?

Answer 6

Some Asian populations and a feature of genetic disorders like Trisomy 21, Noonan’s Syndrome and Zellweger Syndrome

Question 7

What are the 4 different types of epicanthus?

Answer 7

1) Tarsalis
2) Inversus
3) Palpebralis
4) Superciliaris

Question 8

What is Tarsalis?

Answer 8

A type of epicanthus fold. Primarily involves the upper eyelid and then extends medially and dissipates

Question 9

What is Inversus?

Answer 9

A type of epicanthus fold. Most prominent along the lower eyelid

Question 10

What is Palpebralis?

Answer 10

A type of epicanthus fold. Symmetrically involves both upper and lower eyelids.

Question 11

What is Superciliaris?

Answer 11

A type of epicanthus fold that extends from the eyebrow and follows down to the lacrimal sac.

Question 12

What is BPES?

Answer 12

A rare developmental condition affecting the eyelids called ‘Blepharophimosis, ptosis, epicanthus inversus syndrome’ caused by a mutation of the FOXL2 gene

Question 13

What are the 4 facial features at birth of BPES?

Answer 13

1) Narrow Eyes
2) Droopy Eyelids
3) Wide-Set Eyes
4) Upward fold of skin of the inner lower eyelids

Question 14

What are the average IPD’sfor adults and children?

Answer 14

Children - approx 45-55mm
Adults - approx. 55-65mm

Question 15

What pseudo-deviation do wide or narrow IPD’s cause?

Answer 15

Wide = Exotropic
Narrow = Esotropic

Question 16

What is angle kappa/alpha?

Answer 16

It’s the angle between the optical axis and the visual axis that occurs as the fovea isn’t in the geometric centre of the eye (as it’s slightly temporal)

Question 17

What angle kappa gives rise to slightly nasal corneal reflections?

Answer 17

Positive Angle Kappa (PDN)

Question 18

What are other causes of pseudo-squint that aren’t the main causes?

Answer 18

• Corectopia (pupils displaced) - the type of deviation depends on direction of displacement
• Facial Asymmetry - appearance of vertical deviations
• Ectopic Macula - Foveal region displaced by pathology giving rise to a change between visual axis and pupillary line
• Exophalmos - Eyes protrude and can look exotropic. Associated with Grave’s Disease
• Enophalmos - Sunken eyes that can look esotropic. Rarer but seen in orbital blowout fractures.
• Coloboma
• Heterochromia

Question 19

What is Coloboma?

Answer 19

It’s Greek for ‘curtailed’ meaning conditions where normal tissue in or around the eye is missing from birth. It affects the eyelid, lens, macula, optic nerve and UVEA

Question 20

How does Heterochromia cause a pseudo-strabismus?

Answer 20

Where lighter eyes appear more Exo and if partial, the deviation looks to be in the direction of the lighter portion

Question 21

What are the clinical presentation of pseudo-strabismus?

Answer 21

• Health visitors refer
• Typically present at > (or equal to) 6mo
• Thorough case history
• Vague history e.g. unsure of direction, when, etc.
• If improving or not
• No visual concerns
• Photos shown may not be face-on

Question 22

How do we diagnose a pseudo-strabismus?

Answer 22

Diagnosis of exclusion!

• Vision assessment - if occlusion resistant use things like Cardiff Cards. Equal vision is usually a good sign if no squint is present.
• Symmetrical corneal reflections
• Cover test doesn’t show a manifest strabismus
• Check refraction, fundus and media
• Full orthoptic report to prove normal BSV and ocular alignment e.g. overcome 20PD and stereopsis

Question 23

How do we manage a pseudo-strabismus?

Answer 23

The majority of the time it doesn’t require active management!
- Reassure parents
- Explain development of nasal bridge (or whatever it may be)
- Family history of squints
- Can discharge at 1st visit if VA is good and have BSV
- Ask parents to come back if it doesn’t resolve with time. If unresolved it may require surgery or cause management if the epicanthus persists and remains large, that they have ptosis or other lid anomalies or have craniofacial disorders