What is a Heterotropia?
Also known as a stabismus, it is a manifest deviation, wherein the eyes are misaligned under normal binocular viewing conditios |
Tropias may be constant or intermittent |
Tropias may affect one eye or alternate between both |
In early childhood, tropias may cause an amblyopia (lazy eye) |
Tropias may or may not be linked to refractive error |
Tropias may or may not be linked to accommodation and convergence |
A comitant heterotropia is one where the angle of deviation remains the same in all directions of gaze, regardless of which eye they use
Heterotropia Classification
Esotropia |
Exotropia |
Hyper/Hypotropia |
Cyclotropia |
Microtropia |
Pseudostrabismus
Patients look like they have a strabismus but they don't |
Common in children with epicanthal folds as it mimics esotropia |
Also patients with a positive angle Kappa, where the corneal light reflex is displaced nasally, can look like they have an exotropia |
Here, you should perform a cover test to double check |
IPE: Accommodative
Esotropia disappears when the hypermetropia is fully corrected |
Usually arises between 2-5 years |
Amblyopia is uncommon unless the hypermetropia has been uncorrected for a long time. E.g. the problem not picked up at an early age |
Usually normal BSV with glasses on |
Management - perform cycloplegic refraction and issue a full prescription.
Treat the amblyopia if present.
If there's low amounts of hypermetropia and astigmatism, exercises might help to reduce the need to wear glasses as child gets older (over 8)
Most patients will always need to wear glasses or contact lenses
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Investigation: Key Things to Note
Their age - if young, it may be linked to amblyopia and impact their visual development, if a little older, was it acquired? |
If the tropia is new or longstanding |
Is it causing any symptoms? |
Is it present all the time, why not if not? |
Are any adaptations present? |
Is referral required? |
Investigation: Concluding Information
The type of test you perform and the expected outcome depends on your preliminary diagnosis |
Usually, if the tropia isn't causing a problem, then it isn't much of a worry. Measurements may be helpful to monitor. Tailor your test to their binocular status and move on |
If the tropia is causing a problem and the px is symptomatic, they warrant further investigation |
In young children, squints need careful investigation to determine the cause and appropriate management!! |
Esotropia
Primary Esotropia |
Secondary Esotropia |
Consecutive Esotropia |
Constant: partially accommodative or non accommodative |
Results from a loss of vision |
Due to a surgical overcorrection of an exotropic strabismus |
Intermittent: fully accommodative, convergence excess, relates to fixation distance e.g. at distance or near, non-specific |
CPE: Non-Accommodative
Esotropia present all the time and unaffected by the accommodative state |
Deviation may alter between both eyes |
For example, infantile esotropia. Has an early onset in the first year of life usually before 6 months and is a large angle often >30. Could be an alternating deviation, thus VA good in both eyes Dissociated vertical deviation may be present Not associated with hypermetropia |
Management - correct the refractive error and treat the amblyopia. May require surgery to align the visual axes and allow normal BSV to develop. Best to perform before they're 2. |
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Investigation: Relevant Clinical Tests
Case history alongside observing patient |
Visual acuity at both distance and near |
Cover test with and without prism bar |
Refraction |
Ocular motility |
Suppression tests e.g. worth 4 dot test, 4 base out prism |
Accommodation and Covergence |
Bagolini lenses |
Patient investigations would depend on whether the tropia is new or longstanding (esp. in an adult), depend on whether patient is a child, and whether the tropia is constant or intermittent
CPE: Partially Accommodative
Esotropia present at all time and increases in size when patient accommodates |
Deviation size reduces when the hypermetropia is corrected but it is still present |
Occurs in early childhood (ages 1-3) |
Anomalous retinal correspondence may be present |
Dissociated vertical deviation may be present (different from vertical tropia where only 1 eye deviates upwards) |
Management: fully correct the refractive error, treat the amblyopia (as they're children!), only refer for surgery in extreme cases |
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