The A and V syndromes are a graphic description of the variation in the amount of horizontal strabismus as the patient looks up and down. These exist in both esotropia and exotropia. The A-type esotropia demonstrates an increase in the internal strabismus on upward gaze, and a decrease on downward gaze (Fig. 1A). The V esotropia presents more strabismus in the down position and less in the up (Fig. 1B). Exotropia with A phenomenon has more outward deviation in depressed gaze and less in elevated gaze (Fig. 2A). The V exotropia is the opposite, with the greatest amount of outward deviation while looking up (Fig. 2B).
This variation in the amount of strabismus ranges from insignificant to as high as 80 D. Often there is an accompanying over or underacting vertical muscle, particularly the obliques. The V syndromes may have overacting inferior obliques, while in the
MILLER JE. Vertical Recti Transplantation in the A and V Syndromes. Arch Ophthalmol. 1960;64(2):175-179. doi:10.1001/archopht.1960.01840010177002