The visual acuity

Definition

Visual acuity (visual acuity, visual acuity, minimum separable) indicates the measurable degree of ability to recognize patterns and contours in the outside world as such.

Minimum visibile

Minimum visibile is the limit of visibility. This is reached when objects that are viewed and imaged on the retina can no longer be distinguished as contour and contrast from the luminance of their surroundings. The recognizability of external objects thus depends essentially on how our visual system can perceive differences in brightness.

Minimum discriminibile

Minimum discriminibile is the threshold of detecting the smallest differences of external objects. In vision tests it is checked whether a continuous line can be distinguished from a so-called nonius arrangement when looking at a line (nonius visual acuity). In addition, it should be determined whether a minimal movement or tilting of two objects is detected.

Minimum separable

The minimum separable (synonyms: angular visual acuity, visual acuity) requires both a relative localization and a differentiation of directly adjacent contours, which can just about be recognized as separate due to very small differences in luminance on the retina. The closer the patterns are to each other in the outer space, the more the luminance distributions of the neighboring objects overlap.

Minimum legibile

This indicates the reading acuity. Its value is usually higher than the value of the other types of visual acuity, because here words can be recognized not only by the appearance of the letters, but can also be classified according to the meaning of the context.

Relevance of visual acuity

In ophthalmology, visual acuity is the target parameter around which all opthalmological (ophthalmological) measures revolve. There are important legal regulations that require certain minimum visual acuity values for the operation of dangerous devices (e.g. motor vehicles) or for certain professions (e.g. police officers). There are also benefits from private and statutory accident insurances for eye damage and the payment of the statutory blind person’s allowance mainly according to visual acuity.