Eye and Vision

The middle layer of the eye, called the uveal tract, comprises the iris, ciliary body, and choroid. The iris -- the pigmented segment, which might be blue, green, brown, or another color -- forms a ring around the pupil, a black hole in the iris's... Full Answer

As eyes age, eyelid muscles weaken, and skin becomes thinner and more flaccid. This can cause the upper lid to droop or the lower lid to sag. Eyelashes and eyebrows may lose their lushness and thin out considerably.Tear production also drops off, and the... Full Answer

Behind the lens of the eye (which focuses light rays on the retina, the thin, light-sensitive inner layer at the rear of the eye) is the vitreous humor. This clear, stable gel, which looks like raw egg white, supports and fills the rear two-thirds of the... Full Answer

Serious age-related eye problems can cause vision loss or visual distortion that glasses can't fix. More than one million Americans older than 40 are considered legally blind, which means their vision is 20/200 or worse in their best eye, even with... Full Answer

Despite its reputation as a delicate organ, the eye is remarkably resilient and hardy, engineered by nature to last from infancy through old age. Shaped like a sphere, the eyeball is about an inch in diameter, with a slight protrusion in front. It sits... Full Answer

Just behind the pupil (the black hole in the center of your eye) and iris (the colored part of your eye), lies the crystalline lens, which is connected at its outer rim to the ciliary body by ligaments called zonules. The lens focuses light rays on the... Full Answer

Sight is not fully developed at birth; the brain and eyes have to learn to work together in the first months of life. Once sight is well developed, the eyes and the brain team up to provide virtually instantaneous visual information.Consider what happens... Full Answer

The aqueous humor (watery fluid that nourishes the eye) is found principally in the space between the iris (the colored part of your eye) and the cornea (the clear part of the eye's protective covering), and is known as the anterior chamber. The fluid... Full Answer

Choroid is a thin layer of tissue that is part of the middle layer of the wall of the eye, between the sclera (white outer layer of the eye) and the retina (the inner layer of nerve tissue at the back of the eye). The choriod is filled with blood vessels... Full Answer

In its simplest sense, your eye works like a camera. The variable opening is called the pupil; there is a lens system, including the transparent covering called the cornea; a reusable "film" is called the retina, with its various sets of muscles; these... Full Answer