Cover Testing Flashcards
The two eyes fixate at the same place after any fusional convergence demand has been overcome
Phoria
The two eyes do not fixate the same place under binocular conditions (unoccluded)
Tropia
What test allows you to quantify a tropia or phoria?
Alternating cover test using the prism bar
If the patient sees the object moving in the same direction as the paddle, the diagnosis is
Exo.
If the patient sees the object moving the opposite direction as the paddle, the diagnosis is
eso
Prescribe
Base out for
Base in for
BO for eso
BI for exo
Prism shifts the ____ of the target towards the line of sigh but does not move the eye from their phoric/tropic position. The eye stays ____ behind the prism, because the image is lined up with the line of sight.
Prism shifts the image.
The eye stays deviated
Plus or minus lenses have no effect on ___ phorias
vertical. Why? Because vertical movement is independent of accommodation. Would need to use BU or BD prism or vertical lenses
Why might a patient have double vision?
Because of the phoric demand and not enough fusional vergence to keep fusion (intermittent trope)
OR because a tropia is present.
If the tropia is a recent onset, the pt will likely report double vision. If the tropia is of long standing duration, the pt will likely suppress and no diplopia is reported.
Trauma? Headaches? Space occupying lesion? Why is this patient all the sudden having double vision?
Intermittent trope
Phoric demand is very high and pt does not have enough fusional vergence all the time to keep fusion.
Can a pt be tropic and phoric at the same time?
NO
Exos have ___ diplopia. What does this mean?
Crossed or heteronymous
This means that the OD image is seen to the pts left and the OS image is seen to the pts right. The image that remains travels in the direction of the paddle.
Esos have ___ diplopia. What does this mean?
Uncrossed or homonymous diplopia
For an exo, their eyes are turned ____ when in their happy place. This means that an image hits ___ on the pts retina, causing the eye to turn in nasally?
Eyes are turned out.
This means that the image hits temporal retina, causing the eye to swing in because it thinks the light is coming nasally.
For an eso, their eyes are turned ____ when in their happy place. This means that the image hits ___ on the patients retina, causing the eye to turn out temporally.
Eyes turned in.
The image light will hit the patients nasal retina, so the patient will think the light is coming from the temporal world and the patient will swing their eye temporally.
