Heterophoria and Strabismus Flashcards
What is a strabismus?
A misalignment of the eye that is present all the time
What is a heterophoria?
A misalignment of the eye that is only present when the eye is covered
Vergence systems that can function but are under stress can…
Achieve BV, but does it under stress and has symptoms of headaches, discomfort and asthenopia
What is convergence insufficiency?
When exophoria is greater at near than distance
What is divergence excess?
When exophoria is greater at distance than near
What is convergence excess?
When esophoria is greater at near than distance
What is divergence insufficiency?
When esophoria is greater at distance than near
What are fusional reserves?
A measure of how much vergence a person has in reserve that can be used to overcome a heterophoria
How do you measure fusional reserves?
Add prism until the patient reports target blur or double. Record blur, break and recovery points in prism dioptres
What are the classifications of a strabismus? (8)
Time of onset (years)
Direction of misalignment
Size of misalignment
Frequency of misalignment
Laterality of misalignment
Distance of misalignment
Comitancy of misalignment
Role of accommodation
In what units do you measure the magnitude of misalignment in a strabismus?
It is measured in prism dioptres. 1^ = 1cm of deviation from 1m away
What is the role of accommodation?
If it is fully accommodative (corrects with glasses on), partially (squint better but not fully corrected when glasses on), non-accommodative (squint unchanged with glasses on or off)
what types of cover tests are there?
Unilateral cover test - to differentiate between heterophoria and strabismus
Alternating cover test - to assess whether there’s any movement and if so to determine direction of misalignment
Alternating cover test with prism bar - to quantify the magnitude of misalignment
