Astigmatism

What you need to know.

What is Astigmatism?

Astigmatism is a vision problem or condition which causes the individual to have blurred vision. Astigmatism is a very common condition and it has been determined that most people have a certain degree of astigmatism. If an individual has a very slight level of astigmatism this might not affect their vision at all and they might be unaware that they have this condition. If the individual has a very high level of astigmatism not only will they experience distorted or blurred vision but they will also experience eye discomfort and headaches (Astigmatism).

Your eyes.

Our eyes are not simple organs. In the very front of our eyes, there is a transparent structure called the cornea. The cornea’s job is to focus the incoming light. Behind the cornea there is a colored membrane which is shaped as a ring called the iris. The iris “has an adjustable circular opening called the pupil, which can expand or contract to control the amount of light entering the eye” (Than, 2010). Right behind the pupil there is acolorless, transparent structure called the crystalline lens. A clear fluid called the aqueous humor fills the space between the cornea and the iris” (Than, 2010). Around the crystalline lens we find the ciliary muscles. These muscles not only keep the crystalline lens in place but they also contract and relax in order to allow us to see objects that are closer to us and objects that are far away. In interior of the eye is filled with a tissue called the vitreous humor.


Astigmatism is caused by either the irregular shape of the cornea, or the curvature of the lens inside the eye. A cornea with an irregular shape or an irregular curvature of the lens will result in the light not being properly focused in the retina. The retina is light sensitive so this causes the blurred vision.

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Your vision.

Our vision is based on the capability of our eyes to perceive electromagnetic rays. The electromagnetic rays “pass through the cornea in the form of light; the cornea focuses the rays as they enter the eye through the pupil, the black aperture at the front of the eye. The pupil acts as a gatekeeper, allowing as much or as little light to enter as is necessary to see an image properly” (Vision: The Visual System, the Eye, and Color Vision, 2015). The iris not only provides an eye color to the individual but it is responsible for acting as the pupil’s stop. “Two layers of iris muscles contract or dilate the pupil to change the amount of light that enters the eye” (Vision: The Visual System, the Eye, and Color Vision, 2015). Then the lens along with the cornea adjust the “focal length of the image being seen onto the back of the eye, the retina. Visual reception occurs at the retina where photoreceptor cells called cones and rods give an image color and shadow. The image is transduced into neural impulses and then transferred through the optic nerve to the brain for processing. The visual cortex in the brain interprets the image to extract form, meaning, memory, and context” (Vision: The Visual System, the Eye, and Color Vision, 2015).

Visual perception.

Perception can be defined as the process “by which the physical energy received by sense organs forms the basis of perceptual experience. Sensory inputs are somehow converted into perceptions of desks and computers, flowers and buildings, cars and planes; into sights, sounds, smells, taste and touch experiences” (McLeod, 2007).


Perception can be defined as the process “by which the physical energy received by sense organs forms the basis of perceptual experience. Sensory inputs are somehow converted into perceptions of desks and computers, flowers and buildings, cars and planes; into sights, sounds, smells, taste and touch experiences” (McLeod, 2007).


There are different theories that try to explain perception. Gestalt theorists “were the first group of psychologists to systematically study perceptual organization around the 1920’s, in Germany” (McLeod, 2007). Gestalt approach to perception is that “parts identified individually have different characteristics to the whole e.g. describing a tree - it's parts are trunk, branches, leaves, perhaps blossoms or fruit. But when you look at an entire tree, you are not conscious of the parts, you are aware of the overall object - the tree. Parts are of secondary importance even though they can be clearly seen” (McLeod, 2007).


There are six Gestalt principles of perception. These are proximity, similarity, common fate, good continuation, closure, and area symmetry. The principle of proximity states that “things which are closer together will be seen as belonging together” (Gestalt Theory of Visual Perception). The principle of similarity states that “things which share visual characteristics such as shape, size, color, texture, value or orientation will be seen as belonging together” (Gestalt Theory of Visual Perception). The principle of common fate states that if items which are similar and in proximity are moved they might look like a whole. The principle of good continuation states that we have a preference for continuous figures. The principle of closure states that “we have a tendency to close” simple figures such as demonstrated in the picture of the triangles above. The principle of symmetry states that symmetrical figures are seen as closed figures.

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Treatment

Individuals who have this condition have several options which include eyeglasses, contact lenses, orthokeratology, and laser and other refractive surgery procedures.

References

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

Gestalt Theory of Visual Perception. Retrieved from: http://www.users.totalise.co.uk/~kbroom/Lectures/gestalt.htm

McLeod, S. (2007). Visual Perception Theory. Retrieved from: http://www.simplypsychology.org/perception-theories.html

Than, K. (February 10, 2010). How the Human Eye Works. Live Science. Retrieved from: http://www.livescience.com/3919-human-eye-works.html

Vision: The Visual System, the Eye, and Color Vision (August 20, 2015). Boundless Psychology. Retrieved from: https://www.boundless.com/psychology/textbooks/boundless-psychology-textbook/sensation-and-perception-5/sensory-processes-38/vision-the-visual-system-the-eye-and-color-vision-161-12696/

Image references

Image 1, Astigmatism. Retrieved from: http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/astigmatism?sso=y

Image 2, eye. Retrieved from: http://www.passmyexams.co.uk/GCSE/physics/use-of-lenses-for-correcting-vision-eyesight.html

Image 3, vase/faces. Retrieved from: http://vanseodesign.com/web-design/gestalt-principles-of-perception/

Image 4, tree. Retrieved from: https://www.pinterest.com/pin/455567318529203422/

Image 5, triangles. Retrieved from: https://simple.wikipedia.org/wiki/Gestalt_psychology