Cover test Flashcards
What does the cover test ask?
What is the position of rest
What is the cover test?
Objective evaluation of a patient’s ocular posture/alignment
What is a phoria?
Eyes are aligned under binocular conditions, but misaligned under dissociated conditions
What is dissociation?
Retinal disparity input is temporaily removed
What defines phoria?
Magnitude and direction
Orthophoria
Straight alignment with dissociation, equal tension of EOMs on globe horizontal and vertical
Esophoria
Inward alignment with dissociation
Exophoria
Outward alignment with dissociation
Hyperphoria
Upward alignment with dissociation
Hypophoria
Downward alignment with dissociation
What is a tropia?
Only one eye is aligned under binocular conditions at least part of the time
What are the defining characteristics of a tropia?
Magnitude Frequency Laterality Directionality Comitancy
What does the unilateral cover test determine?
Presence/absence of tropia
Direction
laterality
Frequency
When do you diagnose a tropia?
On the cover stroke
What are the three possibilities if neither eye moves on the uncover stroke?
Previously uncovered eye maintains fixation and the covered eye does not fuse
Undetectable small angle re-fusion
Orthophoria
Why would one eye move on the uncover stroke?
Regaining of fusion from dissociated position
What are the two possibilities if both eyes move on the uncover stroke?
Preferred eye is regaining fixation, opposite eye moves due to herring’s law
Preferred eye regains fixation, then fusion movement
Why do we do the alternating cover test?
To prevent fusion of eyes
What does the alternating cover test determine?
Magnitude
Why do the unilateral before the alternating?
If alternating was first, could force the patient to become tropic
How do you record a cover test result?
Magnitude, frequency, laterality, direction
How do you neutralize an exophoria?
Base in
How do you neutralize an esophoria?
Base out
How do you neutralize a hyperphoria?
Base down
How do you neutralize a hypophoria?
Base up
How do we hold a prism for neutrality?
Frontal plane position parallel with the plane of glasses
What is the expected normal finding?
Ortho or low exo at distance and a mild exophoria at near
How does the target move for an exo?
In the same direction as the paddle
How does the target move for an eso?
In the opposite direction of the paddle
How does the target move for a hyper?
Down
How does the target move for a hypo?
Up
