Interpretation of examination results

The two circles of light are superimposed only when they are pictured on “retinal sites with the same lines of sight”. Misalignment of the two circles of light represents strabismus. Its severity can be read from the co-ordinate system of the screen. Although in theory readings have a high degree of accuracy, because the dot pitch of the co-ordinates is 0.5° in all directions of gaze, the angle itself is only of subordinate significance for the assessment. The overall picture formed by the light positions, as marked by the patient in the main directions of gaze and documented graphically by the ophthalmologist in a diagram, is more important. In the case of heterophoria or acute strabismus (concomitant strabismus) all measuring points are displaced in the same way and the resulting octagons are about the same size in the diagram with both right and left fixation. In eye muscle paresis by comparison they are bent out of shape in a typical way and in addition one field is reduced and the other enlarged. When testing the eye affected by paresis, during which the unaffected eye leads, the measuring points do not achieve the values in the guidelines (fixed points). This deviation corresponds to primary strabismus. The resulting polygon is contracted in the direction of pull of the paretic muscle. During testing of the eye unaffected by paresis, when the paretic eye leads, the values in the guidelines are exceeded and the polygons are enlarged accordingly. This deviation corresponds to secondary strabismus.