Acuity

Acuity is the sharpness or keenness of a person’s sensory perception, typically used to describe how precisely a sense can detect detail. The term comes from Latin acuitas, meaning sharpness, and in medical contexts it often refers to the resolvable detail or discrimination capability of a sensory system.

Visual acuity is the ability to discern fine details and shapes. Clinically, it is assessed with standardized charts (for example, Snellen) at a specified distance, and results are recorded as a fraction such as 20/20, indicating the tested distance over the distance at which a normal person can discern the detail. LogMAR is another scale used in research. Visual acuity can be corrected with lenses; impairments may result from refractive error, cataracts, macular disease, optic nerve damage, or neurological conditions. Aging commonly reduces visual acuity.

Auditory acuity refers to the sharpness of hearing and is typically assessed with pure-tone audiometry, yielding thresholds in decibels hearing level (dB HL) across frequencies, or through speech reception measures. Higher thresholds indicate poorer auditory acuity. Other modalities describe acuity more broadly: tactile acuity (two-point discrimination) and olfactory or gustatory acuity (thresholds for odors or tastes), reflecting sensory discrimination capability in their respective modalities.

In practice, acuity is a relative measure of perceptual precision rather than an absolute function. Tests vary by modality and context, and results can be influenced by attention, fatigue, lighting, equipment, and testing conditions. Impairments in acuity can indicate underlying pathology, guide diagnosis, and help monitor treatment or progression.