How the Eye Works

Before we discuss Lasik Eye Surgery, lets examine how the eye works. First, we will identify some of the major parts of the eye and their functions.

Tear Film-

Tear film is a thin layer outside of the cornea that is composed of water, oil and protein. Its chief functions are to moisten the cornea and absorb light rays. People who suffer from chronic dry eyes may either lack a tear film, or their tear film has dried out.

Cornea-

The cornea is the outer surface of the eye that functions as the eyes main refracting lens. It bends the rays of light as they enter the eye and focuses them on the retina. The cornea consists of five layers; the epithelium, Bowman’s membrane, the stroma, Descemet’s membrane, and the endothelium.

Iris-

The iris is a colored, round muscle in the middle of the eye that expands and contracts the pupil to adjust the amount of light that enters the eye. The color of the iris is the color of your eyes.

Pupil-

The pupil is the dark opening in the middle of the iris in the center of the eye. The size of the pupil is adjusted by the iris and determines the amount of light that enters the eye. In a dimly lit room, the pupil helps you see by allowing more light to enter the eye. In a bright room the pupil helps protect the retina by contracting and limiting the amount of light that enters the eye.

Crystalline Lens-

The crystalline lens is a soft and flexible lens that sits behind the iris. This lens is controlled by focusing muscles and has the ability to change shape and redirect the angle at which light travels through the eye. Contracting these focusing muscles makes the lens thicker and helps sharpen close blurry images. Relaxing the focusing muscles stretches out the lens and enhances long distance images.

Vitreous Humor-

The vitreous humor is the fluid that fills the eye behind the crystalline lens. This fluid is composed of mainly water and is surrounded by the retina.

Retina-

The retina is the inner layer of the back inside of the eye. It is composed of 10 layers of tissue, nerve cells, pigment cells and blood cells. It contains light receiving photoreceptors called rods and cones. Rods are photoreceptors that are sensitive to black and white, and cones are photoreceptors that are sensitive to color. The retina uses these photoreceptors to convert light into electrical impulses that it sends to the brain through the optical nerve. The brain then transmits these impulses into the images that we see.

Macula-

The macula is the spot on the retina that the ray of light is ultimately focused on.

In summary, all of these parts (and many more not detailed in this narrative) work together as light passes through the eye to make vision possible. Beams of light enter the eye, are refracted, and then ultimately focused on the retina. The retina transfers these beams of light into electrical signals that are sent to the brain. The brain receives these signals and translates them into the images that we see.