Presbyopia

By: Nicole Richardson

The Function of the Eye

The eye is an organ that consists of receptors that are needed and allow for eyesight (Goldstein, 2014). The eyes function as an optic system allowing sight and acknowledgement of different forms, outlines, and structures (Fernald, 2006).

Vision starts when light rays mirror off of an item and than enter into the eyes through the cornea, which is the clear covering on the outside of the eye. The cornea than deflects the light rays that go through the pupil part of the eye, which is the black, round hole in the middle of the eye. Than the colored area of the eye, called the iris, begins to open and shut, which helps to regulate the light that is coming into the eye. The light than reaches the retina, which is a very thin tissue consisting of millions of nerve cells known as rods and cones; all of which are located in the back of the eye. Cones have the ability to create keen central sight and allow for identifying colors and small specifics. Rods allow for seeing out the sides of the eyes as well as recognizing movements and help with vision in lower lighting. These particular cells located in the retina are able to change the light into electrical impulses, which are than transferred to the brain and a form is created (American Optometric Association, n.d.)

Cones are concentrated in the center of the retina, in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details. Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night. These cells in the retina convert the light into electrical impulses. The optic nerve sends these impulses to the brain where an image is produced (American Optometric Association, n.d.)

National Eye Institute (n.d.). The above illustration shows the parts of eye described in the functioning of the eye. It gives a great visual on how to see just how and where the light enters the eye.

Perception

We are able to perceive objects and scenes through perception. "Perception is determined by an interaction between bottom-up processing, which starts with the image on the receptors, and top-down processing, which brings the observer's knowledge into play." (Goldstein, 2014, p. 9) The Gestalt approach also addresses how it is possible to perceive objects based on involvements and knowledge of certain items through structuralism (Goldstein, 2014).

Presbyopia

According to Giorgi (2012), "Presbyopia is a condition in which your eye slowly loses the ability to quickly focus on objects that are close. It is a disorder that affects everyone people during the natural aging process of their eyes." (p. 1, Part 1 of 9: Overview) Aging can lead to the lens becoming hard as well as affecting the muscle fibers, which results in poor vision with items that are in close proximity. Those who are thirty-five or older have a great chance of this eye condition. Some of the symptoms related to presbyopia involve difficulty in seeing smaller items and writing, holding material far out in front of them, having headaches, and experiencing straining of the eyes (National Eye Institute, n.d.)

Presbyopia is treated through corrective eyeglasses, focusing on the reading power (National Eye Institute, n.d.).
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References


Giorgi, A. (2012, July 27). Presbyopia. What is Presbyopia? Retrieved from: http://www.healthline.com/health/presbyopia#Overview1

Goldstein, E.B., (2014). Sensation and Perception (9th Ed.). Belmont, CA: Wadsworth, Cengage Learning.

National Eye Institute (NEI), (n.d.). Diagram of the Eye. Retrieved from: https://nei.nih.gov/health/eyediagram

National Eye Institute (NEI), (n.d.). Facts about Presbyopia. [Illustration] Retrieved from: https://nei.nih.gov/health/errors/presbyopia