2. COVER TEST IS QUALITATIVE MEASUREMENT OF
STRABISMUS.
PREREQUISITES OF COVER TEST
patient should be co-operative enough to fixate a
target.
Should have sufficient vision to see target
Should have central fixation in both eyes .
Latent nystagmus should not be present.
3. Methods of cover test
1.Direct cover test
Aim : it conforms the presence of a manifest squint.
Procedure
Fixate with both eye at a point
Normal looking eye is covered and movement of uncovered
eye is noticed.
if uncovered eye takes the fixation in opposite direction
,manifest squint is present.
6. Cover uncover test
AIM : it establishes the presence and type of heterophoria .
Procedure:
Performed after direct test conforms absent of manifest
deviation
one eye covered with occluder and other is made to fixate.
In presence of heterophoria the eye under cover
deviates(fusion is interrupted)
Cover is moved quickly and direction of movement tells the
type of heterophoria
7. Alternate cover test
it is performed to establish whether the squint is unilateral or
alternate and also to differentiate concomitant squint from
paralytic squint .
Procedure :
Pt. is asked to fixate alternately ,placing occluder alternately.
It is important to place occluder alternately several times to
dissociate the eye and maximize the deviation.
Occluder should be transferred quickly from one eye to other to
prevent fusion.
8. Observations:
In presence of alternate squint either eye fixates and opposite
eye under cover deviates and maintains the position of
deviation on removing the cover.
In presence of unilateral squint , after removal of cover always
normal eye takes up the fixation and opposite deviates.
In concomitant squint ,primary deviation is equal to secondary
deviation and in paralytic squint secondary deviation is greater
then primary
