What does visual acuity refer to?

Visual acuity describes the ability of the eyes and the visual system to recognise objects, details and contours.

Visual acuity, the percentage of visual acuity, and the required prescription in dioptres are measured during a refraction test or eye examination. The dioptres indicate the strength of the necessary correction. Negative values correct short-sightedness, whilst positive values correct long-sightedness. The strength of the necessary correction may differ between the right and left eyes.