Normal eyes will be aligned in the same direction, without deviation. Have the child focus on a stationary target. Place a hand or cover in front of one eye, and observe the other eye. Movement of the observed eye is abnormal and demonstrates the presence of strabismus. As the covered eye is uncovered, observe it for movement.
Movement is abnormal and indicates the presence of heterophoria.
While wearing polarized glasses, the child views test cards that contain fields of random dots. If stereopsis is present, the child will see a form stand out from the background of the cards. Use the test with the highest level of difficulty that the child is capable of performing. In general, the Snellen tests are too advanced for preschool-aged children. Using a distance of 10 feet for young children may result in better compliance because of closer interaction with the examiner.