Testing for strabismus
There are three tests
used for Strabismus. The Hirschberg test using a penlight determines
the type and degree of Strabismus. The Cross-over test reveal latent
as well as manifest Strabismus. Finally the Cover-uncover test which reveal latent Strabismus. The tests are generally performed in that order. Sometimes the optometrist will also use a prism to do these tests The
Hirschberg test To determine the type
and degree of Strabismus use a small penlight and direct it toward the eyes.
The reflected point of light will reveal the type and degree of Strabismus.
Normal eyes will have the light in the center of the pupils. Note that 1 mm
displacement (Positive or negative angle Kappa) is considered
The
Cover-uncover test In some cases latent Strabismus,
heterophioria, is present, the eye will normally be kept straight by fusion.
To discover the latent deviation cover one eye with some translucent material
through which you can detect any movement of the eye. If there is movement of
the eye when the occluder is removed then there is latent Strabismus. The
latent deviation will be revealed with either eye covered. The
cross-over test As the name suggest in
this test an occluder is transferred from one eye to the other without interval.
The longer the occluder is left over one eye before transferring it without
an interval to the other eye, the more disruptive it is to fusion, tending
to reveal the full extent of any Strabismus. This test show any latent
as well as manifest deviation.
