What Is Fusional Reserve

The fusional reserves are the maximum amount the eyes can converge (positive fusional reserves, measured with base out prism) or diverge (negative fusional reserves, measured with base in prism) while still maintaining BSV. As the image doubles, the break point is reached.

How is Fusional Reserve measured?

The fusional reserve that opposes the heterophoria is measured first (convergent, using base-out prisms, for exophoria), to blur point (if present), break point, and then the prism is reduced until the recovery of single vision.

What is Fusional dysfunction?

Fusional vergence dysfunction (FVD) is a binocular vision disorder with an unknown etiology.1 In this condition, accommodative convergence/accommodation (AC/A) ratio is normal, distance and near heterophorias are within the expected values, and accommodative function is intact, but fusional vergence findings are …