Enkellinsögon

Enkellinsögon is a Swedish term used to describe an eye that relies on a single optical element to form an image, in contrast to compound or mosaic eyes that consist of many separate optical units. The term is commonly used in educational and informative contexts to distinguish camera-type eyes from eyes built from multiple facets.

Definition and morphology: A typical enkellinsögon contains a cornea, a lens that can change shape (accommodation), a vitreous body, and a retina where the image is projected. Light is focused by the cornea and lens onto the retina, allowing the animal to form a sharp image. The retina, together with neural processing, translates light into visual perception. In many camera-type eyes, a specialized central region provides higher acuity.

Occurrence: Single-lens or camera-type eyes are found in a range of animals, notably many vertebrates, including humans, and some mollusks such as cephalopods. This contrasts with the compound eyes typical of many insects and crustaceans, which are built from numerous ommatidia and form images differently.

Function and evolution: The camera-type eye achieves high spatial resolution through precise optics and retinal sampling. Its evolution is an example of convergent evolution, having arisen independently in different groups. Optical limitations include aberrations and sensitivity to lighting conditions, but the basic arrangement supports detailed vision over a variety of environments.

Applications and context: In medical contexts, artificial single-lens optics are used in intraocular lenses to restore vision after cataract surgery. In technology, imaging systems often emulate single-lens principles, balancing light collection, depth of field, and resolution to mimic natural enkellinsögon performance.

See also: eyes, camera-type eye, compound eye, intraocular lens.