Nearly everyone is born with it. It is more sensitive than the best scientific equipment we possess today, being capable of detecting a particle smaller than an atom. Without it, we would have no idea what the difference would be between a blue mustang and a yellow mustang of the same model, or the difference between white and black. What are we talking about? You guessed it: the eye. Without it, we would not have vision.
Vision is important to most people. We would have difficulty navigating our surroundings and writing articles, like this one, if we did not have it. Millions of people around the world do all they can to improve their sight. Some get contact lenses and glasses, spending hundreds of dollars, while others receive laser-eye-surgery, spending thousands. This question should be of interest to those who want to have good vision: “How do we see images?”
To answer this question, we must first take a quick look at the basic components of the human eye. The human eye is a complex organ, more sensitive than any device created by scientists or engineers. The components of the eye that are visible from the outside include the sclera, the cornea, the iris, the pupil, the lens, and the anterior and posterior chambers. Just like a digital camera, the eye has a dark interior, a diaphragm for contro
lling light levels, a sensor for capturing the images projected on it, and a lens that automatically focuses (8). The sclera is the white part of the eye. Like a camera’s interior, the sclera is brown, or dark, on the inside. This allows it to absorb light to keep the images received by the brain from being washed out. Connecting to the sclera and covering the iris is a transparent membrane called the cornea. The cornea is a crystal-clear membrane which consists of five layers, totaling half a millimeter thick (2). It alone accounts for two-thirds of the eye’s focusing power (2).
Lying directly underneath the cornea is the iris, which contains the pigment melanin. Melanin in the iris can produce varying shades of blue, green, and brown, depending on the amount and distribution of the melanin. The iris encircles a hole called the pupil. As the iris sphincter muscle contracts or expands, the iris changes size, causing the pupil diameter to expand to a maximum of 7 millimeters or contract to a minimum of 3 millimeters (6).
Vision is important to most people. We would have difficulty navigating our surroundings and writing articles, like this one, if we did not have it. Millions of people around the world do all they can to improve their sight. Some get contact lenses and glasses, spending hundreds of dollars, while others receive laser-eye-surgery, spending thousands. This question should be of interest to those who want to have good vision: “How do we see images?” To answer this question, we must first take a quick look at the basic components of the human eye. The human eye is a complex organ, more sensitive than any device created by scientists or engineers. The components of the eye that are visible from the outside include the sclera, the cornea, the iris, the pupil, the lens, and the anterior and posterior chambers. Just like a digital camera, the eye has a dark interior, a diaphragm for contro
lling light levels, a sensor for capturing the images projected on it, and a lens that automatically focuses (8). The sclera is the white part of the eye. Like a camera’s interior, the sclera is brown, or dark, on the inside. This allows it to absorb light to keep the images received by the brain from being washed out. Connecting to the sclera and covering the iris is a transparent membrane called the cornea. The cornea is a crystal-clear membrane which consists of five layers, totaling half a millimeter thick (2). It alone accounts for two-thirds of the eye’s focusing power (2). Lying directly underneath the cornea is the iris, which contains the pigment melanin. Melanin in the iris can produce varying shades of blue, green, and brown, depending on the amount and distribution of the melanin. The iris encircles a hole called the pupil. As the iris sphincter muscle contracts or expands, the iris changes size, causing the pupil diameter to expand to a maximum of 7 millimeters or contract to a minimum of 3 millimeters (6).
