Lens (anatomy)

The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation (see also below). Accommodation is similar to the focusing of a photographic camera via movement of its lenses. The lens is more flat on its anterior side than on its posterior side.

The lens is also known as the aquula (Latin, a little stream, dim. of aqua, water) or crystalline lens. In humans, the refractive power of the lens in its natural environment is approximately 18 dioptres, roughly one-third of the eye's total power.

Structure

The lens is part of the anterior segment of the eye. Anterior to the lens is the iris, which regulates the amount of light entering into the eye. The lens is suspended in place by the suspensory ligament of the lens, a ring of fibrous tissue that attaches to the lens at its equator and connects it to the ciliary body. Posterior to the lens is the vitreous body, which, along with the aqueous humor on the anterior surface, bathes the lens. The lens has an ellipsoid, biconvex shape. The anterior surface is less curved than the posterior. In the adult, the lens is typically circa 10 mm in diameter and has an axial length of about 4 mm, though it is important to note that the size and shape can change due to accommodation and because the lens continues to grow throughout a person's lifetime.

Lens

Lens may refer to:

Optics

Other radiation focus and forces

Places

Lens (surname)

Lens is a surname. Notable people with the surname include:

Lens, Switzerland

Lens is a municipality in the district of Sierre in the canton of Valais in Switzerland.

History

Lens is first mentioned in 1177 as de Lenz.

Geography

Lens has an area, as of 2009, of 13.9 square kilometers (5.4 sq mi). Of this area, 5.07 km² (1.96 sq mi) or 36.4% is used for agricultural purposes, while 5.48 km² (2.12 sq mi) or 39.4% is forested. Of the rest of the land, 2.74 km² (1.06 sq mi) or 19.7% is settled (buildings or roads), 0.1 km² (25 acres) or 0.7% is either rivers or lakes and 0.46 km² (0.18 sq mi) or 3.3% is unproductive land.

Of the built up area, housing and buildings made up 11.2% and transportation infrastructure made up 4.0%. while parks, green belts and sports fields made up 3.8%. Out of the forested land, 33.6% of the total land area is heavily forested and 5.8% is covered with orchards or small clusters of trees. Of the agricultural land, 0.4% is used for growing crops and 11.6% is pastures, while 9.1% is used for orchards or vine crops and 15.3% is used for alpine pastures. All the water in the municipality is in lakes.

Eye

Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex.

Bud

In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have the potential for general shoot development. The term bud is also used in zoology, where it refers to an outgrowth from the body which can develop into a new individual.

Overview

The buds of many woody plants, especially in temperate or cold climates, are protected by a covering of modified leaves called scales which tightly enclose the more delicate parts of the bud. Many bud scales are covered by a gummy substance which serves as added protection. When the bud develops, the scales may enlarge somewhat but usually just drop off, leaving on the surface of the growing stem a series of horizontally-elongated scars. By means of these scars one can determine the age of any young branch, since each year's growth ends in the formation of a bud, the formation of which produces an additional group of bud scale scars. Continued growth of the branch causes these scars to be obliterated after a few years so that the total age of older branches cannot be determined by this means.

Eye (magazine)

For the Toronto-based weekly see Eye Weekly.

Eye magazine, the international review of graphic design, is a quarterly print magazine on graphic design and visual culture.

History

First published in London in 1990, Eye was founded by Rick Poynor, a prolific writer on graphic design and visual communication. Poynor edited the first twenty-four issues (1990-1997). Max Bruinsma was the second editor, editing issues 25–32 (1997–1999), before its current editor John L. Walters took over in 1999. Stephen Coates was art director for issues 1-26, Nick Bell was art director from issues 27-57, and Simon Esterson has been art director since issue 58.

Frequent contributors include Phil Baines, Steven Heller, Steve Hare, Richard Hollis, Robin Kinross, Jan Middendorp, J. Abbott Miller, John O’Reilly, Rick Poynor, Alice Twemlow, Kerry William Purcell, Steve Rigley, Adrian Shaughnessy, David Thompson, Christopher Wilson and many others.

Other contributors have included Nick Bell (creative director from issues 27-57), Gavin Bryars, Anne Burdick, Brendan Dawes, Simon Esterson (art director since issue 58), Malcolm Garrett, Anna Gerber, Jonathan Jones, Emily King, Ellen Lupton, Russell Mills, Quentin Newark, Tom Phillips, Robin Rimbaud, Stefan Sagmeister, Sue Steward, Erik Spiekermann, Teal Triggs, Val Williams and Judith Williamson.