What Is a Moderate Astigmatism?

Astigmatism is a very common visual disorder created by abnormal or irregular curvature of the cornea, which causes light to bend irregularly as it passes through the lens of the eye, generating distortions in the formation of the visual image on the retina. Clear, focused vision depends upon light passing evenly through the lens and forming a focused image on the retina. The most common symptom of astigmatism is blurry vision in both near and distance vision.
Astigmatism can be measured by the amount of lens power, the focal length of the lens used to correct the astigmatism to perfect, clear vision. In a sense, the astigmatism can be seen as a natural lens that throws the vision off, and the corresponding lens of equal but opposite power is the lens used to correct the vision. Lens power is measured in diopters, which is the focal length of the lens, or the distance from the lens at which a perfect, clear image is formed. Depending on whether the lens is concave or convex, the diopters are noted in positive or negative numbers, with negative diopter being concave, and positive diopter being convex.
Most people have some astigmatism, though it is so mild that no symptoms are noticed. Moderate astigmatism is defined as astigmatism of 1.0 to 3.0 or 4.0 diopters, depending upon the agency defining astigmatism.
Moderate astigmatisms are usually corrected through the use of the lens of appropriate diopter built into the lens of the patient's glasses. Lenses that correct astigmatism are called toric lenses. Some astigmatic conditions can be corrected with hard contact lenses that reshape the cornea, called toric contacts. Several surgeries, including laser or lasik eye surgeries as well as traditional scalpel surgical techniques, are used to correct astigmatisms of mild or moderate severity. These surgeries do correct the astigmatism, but are not without their risks. According to the FDA, there are small but significant risks of post-surgical complications, including permanent blindness, visual distortions such as halos or cloudiness, or severe dry eyes,
A group of European, Canadian, and American cranial osteopaths and optometrists maintain that many eye disorders, including astigmatism, are due to imbalances in the external muscles of the eye which control movement of the eye that cause the shape of the eye to distort. This group believes that most eye disorders can be treated with correct eye exercises or a combination of eye exercises and lenses. While considerable skepticism remains in the mainstream medical and optometric communities, a small body of evidence suggests that eye exercises are helpful in certain disorders such as convergence insufficiency, evidence is limited and more research is needed to produce convincing results for conditions such as astigmatism.