Influence of viewing distance on vertical strabismus.

BACKGROUND

Vertical strabismus can be modulated by the viewing distance. We report on 19 patients with this disorder.

METHODS

The following squint angles were measured by the alternate prism and cover test at a viewing distance of 5 m. At 0.3 m, measurements were taken with and without an addition of 3.0 D to the corrected refraction. Cases of a dissociated vertical deviation were excluded. Fifteen patients underwent surgery. They were reexamined 3 months later.

RESULTS

At a viewing distance of 5 m, the vertical deviation ranged from 0 degrees to 16 degrees (median 7 degrees ). At 0.3 m, the deviation increased by 2 degrees -15 degrees (median 7 degrees ) in 15 patients and decreased by 3.5 degrees -8 degrees (median 4.5 degrees ) in 4 patients. Eleven patients had a strabismus sursoadductorius and one had a strabismus deorsoadductorius. Eye muscle surgery reduced both the vertical deviation for distance fixation to 0 degrees -14 degrees (median 2 degrees ) and the difference between the deviations for distance and proximal fixation to 1 degrees -6 degrees (median 3 degrees ).

CONCLUSIONS

In certain cases, vertical strabismus can be modulated by convergence and accommodation. This condition is frequently associated with an incomitance of the vertical deviation in side gaze. The baseline deviation can be reduced by appropriate eye muscle surgery. In cases of vertical accommodative vergence, bifocal glasses can be helpful.