Astigmatism

Not Getting a Clear Picture

What is Astigmatism?

Astigmatism is a common vision condition that is due to an irregular shaped cornea which prevents light from focusing correctly onto the retina (American Optometric Association, 2015). The result is then blurred vision.


It is important to also note that the shape of the cornea is an irregular curvature of the cornea, in which eyesight is not necessarily "bad" but the cornea is disrupted (Bixler, n.d.). The front surface of the cornea is more curved than the other and light may then come from varying directions as seen below, rather than onto a fixed point.

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Here, the abnormality of light reflection to the retina can be seen in the astigmatic eye. In the eye with normal vision, the direction of light is correctly focused onto the retina creating clear vision. The irregularity in the cornea is found to be responsible for this misdirection of light focus.
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This is what a person with astigmatism might experience. The blurred vision can result from near- or far-sightedness that result in refractive errors and can lead to eye discomfort and headaches (America Optometric Association, 2015).

Perception and the Gestalt Approach

Gestalt uses organizing principles to determine how elements in a scene are grouped together. Some of these principles include:

  • Good continuation - All points when connected are perceived as following the same path.
  • Pragnanz- Patterns seen as structures. The Olympic symbol is an example of pragnanz as it is not seen as nine shapes but as five circles (Goldstein, 2014).
  • Proximity - Things near each other appear grouped together.
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These are some examples of the Gestalt approach. Notice that the concept of Gestalt is based on the grouping, or perceived togetherness of figures.

Scene Perception

The ability to identify a scene after only a small moment of viewing them is known as the gist of a scene (Goldstein, 2014). What permits this quick ability is the information from global image features in which specific scene recognition is based on naturalness, openness, roughness, expansion, and color (Goldstein, 2014). For example, a quick scene of a beach will bring to mind an image of openness, depiction of color of a blue sky, and maybe roughness of crashing waves. Past experiences with scenes allow fast recollection of the environment.

Vision processing to brain processing

Visual perception begins with a stimulus in the environment like a table for example. When light hits this table it is reflected into the eye and is called the principle of transformation. This states that stimuli is transformed from the environment to one's perception (Goldstein, 2014).


Sensory and visual receptors then act to respond to the visual information by changing light energy into electrical energy by user of visual pigment which is called transduction (Goldstein, 2014).


The information from the table is then processed in the brain through complex neural networks and go through another process called neutral processing. The cerebral cortex receives this information and differing lobes of the brain work to coordination the information received from each lobe.


For example, if one tripped into a table and hit their head, the perception of the table afterward might elicit information from the temporal lobe recalling the sound of hitting the table, or information from the parietal lobe in remembering how much hitting the table hurt.


In recognition of this accident, the person's behavioral response may now be to glance at the floor for impeding objects that may cause a trip and fall before going to sit at the table. This response of action is important because it has evolutionary importance as it serves as an importance means of survival to be able to evaluate an object and determine if and what, are obstacles or predators (Goldstein, 2014).

Treatment for Astigmatism

  • Eyeglasses: Compensates for astigmatism and gives greater focus in differing areas of the lens.
  • Contact Lenses: Cannot compensate for the cornea's shape but can provide clearer vision.
  • Orthokeratology: Fitting contact lenses to reshape cornea to be worn for limited periods of time. Not a permanent solution.
  • LASIK surgery: Removal of tissue from inner layer of cornea thereby correcting the abnormal shape.
  • (American Optometric Association, 2015)

References

American Optometric Association. (2015). Astigmatism. Retrieved form http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/astigmatism?sso=y


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


Bixler, J. E. (n.d.). Astigmatism. Retrieved from http://www.kellogg.umich.edu/patientcare/conditions/astigmatism.html


Danti, A. [Photographer]. (n.d.). How images are captured by our eyes and processed by our brain [Photograph]. Retrieved from http://www.shutterstock.com/pic.mhtml?id=200634656&src=id


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


How to cure and treat astigmatism [Photograph]. (2015). Retrieved from http://www.eyesonyouseattle.com/blog/article/BOSVIEW/How-to-Cure-and-Treat-an-Astigmatism/