Advanced Binocular Vision (ABV) Exam 2 Practice 2026 - Free ABV Practice Questions and Study Guide

PRA reflects how well the eyes can increase accommodation when vergence demand rises. During a PRA test, minus lenses are added to stimulate more accommodation; the amount of minus the patient can tolerate before blur indicates their capacity to stimulate accommodation. If someone has accommodative insufficiency, their amplitude of accommodation is reduced, so they can’t generate enough accommodation to clear the image as demand increases. This leads to premature blur because the ability to adequately stimulate PRA is limited. This pattern is distinct from convergence excess or divergence excess, which relate to vergence alignment rather than the capacity to increase accommodation, and from oculomotor palsy, which would produce broader motor deficits.