seende

Seende, in Swedish, denotes the sense of sight or vision—the ability to perceive the environment via light detected by the eyes. It refers to both the anatomical structures that enable seeing and the perceptual experience of images, motion, and color.

Anatomy and physiology

Vision begins when light enters the eye through the cornea, passes the pupil, and is focused by the lens onto the retina. The retina contains photoreceptors called rods, which are highly sensitive in low light, and cones, which mediate color and fine detail. These cells convert light into electrical signals that travel via the optic nerve to the brain, primarily the visual cortex in the occipital lobe, where signals are interpreted into images, movement, depth, and color.

Key concepts

Visual acuity refers to the sharpness of vision and is often measured with a Snellen chart. Depth perception arises from binocular vision and brain processing. Color vision depends on the three cone types that respond to different wavelengths. The field of view and contrast sensitivity also influence seende, as does the brain’s speed of processing visual information.

Development, health, and disorders

Vision develops in infancy and is influenced by genetics, development, and visual experience. Refractive errors—myopia (nearsightedness), hyperopia (farsightedness), and astigmatism—affect focusing. Presbyopia, common with aging, reduces near vision. Eye diseases such as cataracts (lens clouding), glaucoma (optic nerve damage), age-related macular degeneration, and diabetic retinopathy can impair seende and require medical care or intervention.

Variation and technology

Many species have different visual capabilities, with variations in acuity and spectral sensitivity. In humans, corrective lenses, contact lenses, and surgical options (for example, cataract surgery or refractive procedures) are used to maintain or restore seende.