REFRACTIVE CONDITIONS: ASTIGMATISM Definition: Blurred vision due to an irregularity in the shape of the cornea or due to the shape of the lens inside the eye. Astigmatism is the result of an irregularly shaped cornea. There are two types of astigmatism, corneal and lenticular. When astigmatism is caused by an irregularity in the shape of the cornea, it is corneal astigmatism. When it is cause by an irregularity in the shape of the lens, it is called lenticular astigmatism. Corneal astigmatism is the most common. A normal eye has a rounded shape like a ball; however, an eye with astigmatism is shaped more like a football. Astigmatism can cause difficulty focusing at varying distances. Patients with myopia and hyperopia alike can have astigmatism. According to the AOA website “The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can change as a child grows and may decrease or worsen over time.” Lenses are usually prescribed for the patient to help improve acuity. Vision therapy is not a cure for astigmatism, therefore, therapy is performed to help reduce or eliminate the need for prescription lenses. The first image below shows the difference in how the light enters a normal eye and an eye with astigmatism. The second image below shows the difference in the shapes of the cornea between a normal eye and an eye with astigmatism. As with myopia and hyperopia, an eye with astigmatism doesn’t focus properly. Therefore, in therapy, activities that focus on improving flexibility of accommodation would be performed. Those activities would aid in shifting focus from near to far and vice versa more easily. In the process, the patient should see a reduction in the symptoms associated with astigmatism.
Symptoms of astigmatism:
Since examples of activities for myopia and hyperopia have already been discussed and we now know that a patient with either can have astigmatism, your assignment for this discussion is to share with the group an example of an activity that might be performed with a patient that has astigmatism. Please be as descriptive as possible for the benefit of the group. Also, discuss your definition of astigmatism and why you believe therapy is beneficial.
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November 2017
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