Diagnosis of Tropias and Phorias with the Eye Cover-Uncover Test

 

Cover-Uncover Test:

(1) The patient fixes on a target.

(2) An eye is covered for a few seconds, and then uncovered.

(3) Testing is performed for near and distant fixation.

(4) Testing should be done with and without corrective lenses.

 

Testing Steps

 

(1) Cover right eye and observe left eye.

 

(2) If left eye moves, then tropia is present. Uncover right eye and observe both eyes:

(2a) If both eyes move, then there is left monocular tropia.

(2b) If neither eye moves, then alternating tropia.

 

(3) If left eye does not move, then cover left eye and observe the right eye.

(3a) If right eye moves, then tropia is present. Uncover left eye and observe both eyes:

(3a1) If both eyes move, then there is right monocular tropia.

(3a2) If neither eye moves, then alternating tropia.

(3b) If right eye does not move, then no tropia is present. Alternatively cover right eye, then left eye, and observe uncovered eye:

(3b1) If uncovered eye moves, then phoria is present (see table below).

(3b2) If uncovered eye does not move, then no phoria present (orthrophoric).

 

where:

• phoria = latent strabismus

• tropias = manifest strabismus

Newly Uncovered Eye	Newly Covered Eye	Phoria
moves	does not move	heterophoria
does not move, and deviated	does not move	alternating strabismus
assumes fixation	deviates	nonalternating monocular heterotropia present