However, unlike the lens, the shape and focusing power of the cornea are not adjustable. Working in concert with the aqueous humour behind it, the cornea provides the greatest focusing power of the eye. At the front of the eye, the tear film covers the transparent cornea, the “window” through which light passes into the eye. The sclera is itself covered anteriorly by the conjunctiva, a transparent mucous membrane that prevents the eye from drying out.
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The sclera, the tough protective outer shell of the eyeball, is composed of dense fibrous tissue that covers four-fifths of the eyeball and provides attachments for the muscles that move the eye. The eyeball houses the retina-an extremely metabolically active layer of nerve tissue made up of millions of light receptors (photoreceptors)-and all of the structures needed to focus light onto it. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!Įyeball, spheroidal structure containing sense receptors for vision, found in all vertebrates and constructed much like a simple camera.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.
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#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.