Astigmatism

What is it?

According to David Helwig (2013) an astigmatism occurs when the cornea is unable to focus an image to a single point onto the retina which causes a blurred image (Helwig, 2013). The image gets focused in two different locations within the eye instead of a single point. If the cornea is misshapen, it is unable to focus correctly on the light that passes through the cornea. The cornea is supposed to be shaped like a sphere but when it is shaped more like an ellipse or football, the light is bent in different ways and causes the vision to be blurry (Helwig, 2013).

Visual perception

Being able to process a visual stimuli is a seven step process. After seeing the stimuli, the light is reflected through the eye and onto the retina by the principle of transformation and representation (Goldstein, 2014). Next the visual receptors transform the light energy into electrical energy and shaping the perception by the visual pigments. The fourth step involves the neural processing which happens in neurons similar to the retina. The signals travel all the way to the brain. When the signals reach the brain, the visual stimuli is perceived, recognized, and deciding how to act on the stimuli. By perceiving the object, the brain gives it meaning and we are able to recognize it (Goldstein, 2014).


Gestalt theories state a person views the object as a whole and is able to take parts from the whole, but we see the whole object first (Goldstein, 2014). Humans perceive stimuli as a whole object instead of tiny points that make up an object like structuralism viewed perception. Gestalt approach has six different principles that make up the theory including proximity, similarity, common fate, good continuation, closure, and area/symmetry (Breedlove & Watson, 2013).

Treatment options

In order to correct astigmatism cylindrical lenses are needed (Helwig, 2013). Either with contact lenses or glasses, the astigmatism can be corrected by counteracting the curvature of the cornea. According to Helwig (2013), it can take time to fully correct the defect with lenses and may need to be readjusted a couple of times. When wearing contact lenses, it is important to get the lens that is weighted to ensure it will not turn when the eye blinks. A toric lens will help ensure the lens returns to the same spot each time (Helwig, 2013). Another way to correct astigmatism is by laser eye surgery. This option comes with greater risks and may not correct the symptoms completely.

References:

Breedlove, M. & Watson, N. (2013). Biological psychology: An introduction to behavioral, cognitive, and clinical neuroscience (7th Ed.). Sunderland, MA: Sunderland Associates, Inc.


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


Helwig, D. L. (2013). Astigmatism. In B. Narins (Ed.), The Gale Encyclopedia of Nursing and Allied Health (3rd ed., Vol. 1, pp. 350-352). Detroit: Gale. Retrieved from GVRL database.


Flores Eye Clinic [Photograph]. (2014). Retrieved from http://floreseyeclinic.com/education/3023-astigmatism.html


Rutherford Eye Care [Photograph]. (2016). Retrieved from http://www.rutherfordeyecare.com/your-eyes/astigmatism/