NBEO Ocular Motility Practice Test

Fusional vergence ranges show how much the eyes can converge or diverge to keep the image single when misalignment is present. In convergence insufficiency the system’s ability to converge is diminished, so the positive fusional vergence range is reduced. In divergent excess the divergence mechanism is overactive or inadequately compensated, leading to a reduced negative fusional vergence range. Because both conditions involve an insufficient ability to produce or sustain the needed vergence to maintain single vision, a finding of reduced fusional vergence ranges can indicate either convergence insufficiency or divergent excess. The other options don’t point to these vergence control problems: increased accommodation amplitude isn’t a typical marker of these binocular issues, normal vergence ranges with abnormal pursuit suggests a different oculomotor issue, and vertical misalignment alone doesn’t address the vergence dysfunction in question.