One of the ways that we gather information about the world around us and interpret that information is through sight. Light can have an array of wavelengths and amplitudes. Different wavelengths correspond to different colors and different amplitudes determine the perceived brightness. Light rays enter the eye through a transparent tissue called the cornea and through an opening called the pupil. The pupil is surrounded by the colored muscle called the iris which contracts to adjust the size of the pupil. The light then travels through the transparent lens which focuses the light on the retina. The retina consists of two types of light receptors called rods and cones. Cones detect color and rods help us see when little light rays are present. Images that we see are focused on the fovea at the back of the retina. The retina also contains numerous types of neurons such as ganglion cells and bipolar cells. These cells process the light energy into neural impulses. The impulses are transported to the brain via the optic nerve which is located at the back of each eye. The optic nerve leads to the thalamus in the center of the brain. The information then travels from the thalamus to the visual cortex at the back of the brain. This is the location where the neural impulses are interpreted. Without vision, we would not be able to perceive and interpret the information around us.

In order for vision to occur, all of the parts of the eye must be functioning correctly. As people age, it is very possible that cataracts form in the eyes. A cataract is a clouding of the lens of the eye. It is described as looking through frosty glass; everything is fuzzy and unclear. There are different stages of cataracts, but if left untreated, they can cause blindness. My great grandma had cataracts and they were so bad that she could not see to drive, sew, or even cook dinner. Today, there are corrective laser surgeries available that can shave off parts of the lens that are affected. Whenever she had cataracts, there were cataract surgeries, but they were done with a knife and not a laser beam. These surgeries were extremely dangerous. During her surgery, both of her corneas got damaged. The doctors had to cut around the cornea to get to the lens, but they did it incorrectly. Even though her lenses were fixed, the damage to the corneas affected her vision immensely. Even after the cataract surgery, she was still considered legally blind. The cornea is not easily fixed; she waited on the organ transplant list for months until a man who had similarly shaped corneas died in a car crash. After she got new corneas, her vision was restored and she could go back to her normal daily activities (including reading the newspaper!). Without fully functional parts in the eye, it is obvious that there are extreme side effects. We now know that most eye cataracts are caused by the effects of sun damage over time. We have polarized and ultraviolet lenses in sunglasses now to protect from damage to all parts of the eye.