Double Vision and Eye Alignment
Double vision should be considered an ocular emergency. Double vision is assessed by the Eye Doctor with extraocular muscle (EOM) testing, cover test and phoria testing. During EOM testing the Eye Doctor moves a target up, down, and side to side. This test assesses the function of cranial nerves (3, 4, and 6) and the muscles they control. These are the muscles that move the eye in various directions. The cover test is useful for testing eye alignment by measuring the phoria and tropia. A phoria or heterophoria is the natural position of eye alignment. If the eyes are naturally misaligned horizontally or vertically the EOMs can strain to some degree to correct this and keep vision single. If double vision is present, then a tropia is present. For a tropia, eye misalignment is to large to be compensated for. Tropia is known as a strabismus or eye turn. For a new tropia or strabismus double vision results. The brain really dislikes double images and attempts to prevent double visio...