positive relative accommodation

The maximum amount of accommodation that can be stimulated while maintaining clear, single binocular vision at a fixed distance, typically 40 cm. It is measured by adding minus spherical lenses binocularly until the patient reports sustained blur, with the total minus lens power representing the PRA value. High PRA (>2.5D) may indicate accommodative excess or uncorrected myopia, while low PRA (<1.5D) suggests accommodative insufficiency or an over-minused refraction.