MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 3. ANATOMICAL AND PHYSIOLOGICAL ASPECTS OF BODY FUNCTION SELF-REGULATION

GENERAL ISSUES IN THE ANATOMY AND PHYSIOLOGY OF SENSORY SYSTEMS

THE ORGAN OF VISION

2. PHYSIOLOGY OF THE VISUAL SENSORY SYSTEM

2.3. VISUAL ACUITY

Visual acuity refers to the eye's ultimate capacity to distinguish separate objects. It is defined by the minimum distance between two points that the eye can perceive as separate.

Visual acuity depends primarily on the size of the cones: the smaller they are, the higher the visual acuity. Maximum visual acuity occurs in the fovea centralis and decreases toward the periphery of the retina.

For two points to be perceived separately, at least one unexcited cone must lie between two excited ones. Since the diameter of a cone is 3 mкм, distinct Vision requires a retinal image of at least 4 mкм. This image size is produced when the visual angle equals one arcminute. Visual acuity is measured using Sivtsev's charts, which consist of two charts: one featuring letter symbols (optotypes) and the other featuring Landolt rings (broken rings of various sizes). Each chart is composed of 12 rows of optotypes.



Last update: 08/08/2026

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