Neutralizing pattern deviations in ocular motility.

Patients are frequently seen who show heterotropias on gaze in opposite directions, such as an esotropia on looking right and an exotropia on looking left, or a right hypertropia on looking up and a left hypertropia on looking down. These antipodal deviations may occur naturally as a congenital derangement, or may develop as a result of surgery or trauma (Urist, I964). Fortunately, in most cases, they balance one another so that the eyes become straight, that is, vertically and horizontally aligned, in some neutral position of gaze. Because of this balancing tendency and the ability to develop straight eyes, I call them "neutralizing pattern deviations". More than half of about 4,000 cases of strabismus examined over the past 20 years have had at least one type of neutralizing pattern deviation. To mv knowledge there exists no comprehensive report on all types of neutralizing deviations, no classification, and no nomenclature for discussing them. In this paper I shall classify, discuss, and illustrate the types of neutralizing deviations I have seen. Somewhere between the opposite directions of gaze in which opposite deviations occur is the "neutral position" where binocular vision is achieved. It may be a large area or a point, the neutral point, depending on the patient's amplitude of fusion. The neutral position is most commonly located in the primary position, in which the eyes and the head are directed straighit ahead. In some cases it is located in an eccentric position and results in a dissociation between the position of the eyes and that of the head. In these cases the head is turned, the direction depending on the position of the neutral point when the eyes are directed straight ahead. It may be a head turn to the right or left, a head tilt to the right or left shoulder, a head bend up or down, or any combination of these. Cogan (i967) described the neutral point in opposite rapid component nystagmus on gaze in opposite directions as followvs: