Human visual system - Essay Example

However, for one to see, the human eye has to convert the visible light energy into neural activity, a process that usually takes place in the retina part of the eye (Atchison and Smith 2000, P.11). The retina contains neurons, enabling it to transduce light energy into neural activity. However, the process does not take place in a vacuum, rather with the help of rods and cones found in the retina according to Atchison and Smith (2000, P.11). Rods and cones are photoreceptors that are responsible for the conversion of visible light energy into neural activity (Bernstein et al. 2007, P.45).

These photoreceptors usually contain chemicals, which are sensitive to light energy. As such, when light strikes the retina, the chemicals in the rods and cones immediately break apart, generating signals, which are relayed to the brain for interpretation. However, Bernstein (2010, p.91) notes that the process of rebuilding the chemicals broken apart in the rods and cones usually takes some time, which explain why a person usually find it hard seeing when entering a dark room when coming from a bright light.

Nonetheless, as one continues to stay in the dark, the rods quickly build up the chemicals thereby enabling the person to start seeing things normally. This process of adjusting to darkness overtime is usually referred to as dark adaptation where one becomes approximately 10,000 times more light-sensitive after being in the darkness for quite awhile according to Atchison and Smith (2000, P.12). Cones, on the other hand, contain three light-sensitive chemicals that help in determining the color being seen by an individual.

Cones are usually found at the middle of the retina in an area known as the fovea. The fovea is the area where the incoming light is focused. Bernstein (2010, p.91) notes that the density of cones in the fovea differs from one person to another, which explains the differences in visual acuity among different people. What is noted that cones usually works best at high light intensities, where the ability to differentiate colors become active (Bernstein et al. 2007, P.46). For instance, it is possible for one to pick two different socks in a dark room thinking that they resemble each other and only learn later that the socks are actually different in color.

From the retina, signals are transferred to the brain, where the information is translated before an individual is able to see something. However, as Bernstein (2010, p.91) points out, the eye does not just transfer the images it focused on the retina directly to the brain as this will make one see blurred pictures. Instead, the visual images are first sharpened by the eye, a function, which hugely depends on the interaction between the rods and cones, found in the retina of the human eye as noted by Atchison and Smith (2000, P.12). Bernstein (2010, p.91) reveals that rays of light usually pass through numerous structures of the retina before striking the cones and rods.

Once the rods and cones have been struck, they generate signals that are again relayed back to the surface of retina, thereby allowing the ganglion cells and the bipolar cells to connect enabling the eye to start the process of information analysis. Bipolar cells are part of the neurons capable of sending either positive or negative signals