Additional descriptions of the procedures can be found in the lecture material and the laboratory material.
Purpose: To detect the presence of a manifest deviation (tropia) in the alignment of the eyes. The test is performed both at distance and near in the same manner.
The patient is directed to look at a distance (or near card) 20/20 letter with their best correctable vision. The occluder is used to cover one eye. This eye is then uncovered approximatly 1-2 seconds later, enough time to break fusion). The doctor monitors the movement (if any) of the non-covered eye. Do not monitor movement of the covered eye at any time.
If movement is detected inward upon covering the contralateral eye, then an exo movement has been detected. This movement is labeled as an exotropia.
If movement is detected outward upon covering the contralateral eye, then an eso movement has been detected. This movement is labeled as an esotropia.
Additional testing is necessary if movement is detected in either direction to determine if the deviation of the eye is constant or alternating and always present or intermittent.
If no movement of either eye is noted upon the cover/uncover test, then no tropia is present. Continue to the alternating cover test.
Purpose: To detect the presence of a latent deviation (phoria) in the alignment of the eyes. The test is performed both at distance and near in the same manner.
The patient is directed to look at a distance (or near card) 20/20 letter with their best correctable vision. The occluder is used to cover one eye. This eye is then uncovered approximatly 1-2 seconds later and the opposite eye is covered. This action is repeated to cover the eyes in an alternating action.
The procedure is performed identically at near by covering one eye followed by covering the opposite eye.
The doctor monitors the movement (if any) of the un-covered eye. Do not monitor movement of the covered eye at any time.
If movement is detected inward upon covering the contralateral eye, then an exo movement has been detected. This movement is labeled as an exophoria.
If movement is detected outward upon covering the contralateral eye, then an eso movement has been detected. This movement is labeled as an esophoria.
The magnitude of the deviation is estimated and compared to the value found when prism is used to neutralize the movement.
