Cover Test Flashcards
What does the Cover Test determine?
- presence of a deviation
- laterality(which eye)
- frequency of the deviation
- direction of phoria or tropia
- magnitude of deviation
Orthophoria
-the perfect alignment in the absence of a stimulus for fixation
Heterophoria/phoria
- the tendency for the eyes to deviate when fusion is blocked
- small phoria is common for most people
- usually overcome by fusion
- if no movement with cover/uncover test when either eye was covered
Esophoria
-“posture” slightly inward
Exophoria
-“posture” slightly outward
Decompensating phoria
- when motor fusion is no longer enough to overcome the phoria
- can result in discomfort or diplopia
Heterotropia/tropia
- MANIFEST deviation
- visual axes of both eyes do not intersect at fixation
- leads to diplopia or suppression of the deviated eye
Anisometropia
- difference in refractive errors between the two eyes
- can result in tropia
Why tropia?
- anisometropia
- abnormality with extraocular muscles
- eye disease
Cover-uncover test
- unilateral cover test
- helps differentiate..
- presence of a deviation
- laterality
- frequency
- THIS TEST IS ALWAYS DONE FIRST
- DONE IN ALL POSITIONS OF GAZE
Alternating cover test
determines. ..
- direction of deviation
- magnitude of deviation
- cover one eye to break fusion, the alternate between covering eyes to observe movement/direction
- WATCH UNCOVERED EYE FOR REFIXATING AND DIRECTION
What do you do test?
DO NEAR AND DISTANCE BOTH EVERY TIME
“cover” in cover-uncover test
- shows if deviation is phoria or tropia
- evaluates the visual axis of each eye when both eyes are viewing a target
- look at the eye that is not covered
Cover-uncover results
phoria-the visual axis of both eyes are aligned on the target with both eyes open
tropia- the visual axis of one eye is aligned on the target while the other is misaligned with both eyes open
Uncover in cover uncover test
- shows if tropia is alternating or unilateral
- focus on eye not covered to determine if it picks up fixation
- shows if tropia is constant or intermediate
Uncover test results
unilateral tropia: right or lef, one eye usually fixates when both are open
-the tropic eye only fixates when the preferred fixating eye is covered
alternating tropia: patient is able to keep either eye on the target with both eyes open
where should you sit?
-you can see both eyes, but you do not block the patients fixation on the target
Distance?
- at distance, isolate letter that is 1 or 2 lines LARGER than the best corrected VA in poorer seeing eye
- at near, hold target 40cm
- patient may hold target if they start to lose focus
Assess fixation
- determine if the patient is able to fixate with the right eye when the left eye is covered and then check left
- OBSERVE ANY MOVEMENT OF THE RIGHT EYE AS SOON AS THE LEFT EYE IS COVERED. IF NO MOVEMENT, THE RIGHT EYE WAS FIXATING WHEN BOTH EYES ARE OPEN
fusion
- binocular vision
- when switching occluder between eyes, allow a couple seconds to let eyes resume their relationship with each other
- BRING BACK FUSION
Measuring the deviation
- put prism in front of the eye and watch the other
- move occluder back and forth and increase prism until you no longer see movement
- deviation is neutralized at the amount of prism where both eyes appear to be aligned and there is not movement on alternative CT
Exo
-correct with base in
Eso
-correct with base out
Hypo
-correct with base up
Hyper
-correct with base down
Ortho
-verify by sing BI and then BO
Recording!
- cc or sc(if they come in with glasses, make them wear them)
- Distance and Near(use prime)
- amount of prism in prism diopters
- E for eso
- X for Exo
- RH is right hypertropia
- ortho for no deviaion
- P or T
- R,L, alt
- only record vertical phorias and tropias
- () for intermittent
Comitancy
- deviation size remains the same (within 5 diopters) in all positions of gaze
- implies no muscles are underreacting or overreacting
Noncomitancy
- deviation size changes in different positions of gaze
- more than 5 diopters
- due to over action or under action of one or multiple muscles
