‘Astigmatism’ is a Greek term meaning ‘without a mark or spot’. The condition arises most commonly from an irregularly shaped cornea although an irregularly shaped lens of the eye could also result in the condition.
As a result of the slope of the cornea, the image produced by an astigmatic eye may hence be focused on the retina in one plane but in front of or behind it in another. The end result is a difficulty in making out the fine details of a viewed object. Blur may occur differently at varying distances with horizontal and vertical lines appearing wavy if not blur. The likelihood of developing astigmatism often increases with age.
Diagnosing and Describing the Condition
An eye examination can detect the presence of astigmatism and help to define the nature and severity of the condition. The curvature of the front surface of the cornea can be measured and the shape of the cornea can be accurately determined. The refractive error of the eye along with the planes and powers of astigmatism can also be determined.
An ophthalmologist may describe the condition based on specific eye structures, the axis resulting in blur or by the focusing ability of the eye. A structural lack of symmetry resulting from an irregularly shaped cornea can give rise to corneal astigmatism while that arising from an irregularly shaped lens leads to lenticular astigmatism.
If looked at by axis, astigmatism can be split into regular and irregular forms. Regular astigmatism can then be further sub-classified into against-the-rule, with-the-rule and oblique astigmatism. Research has shown that with-the-rule astigmatism can trigger the development of myopia.
By focus, astigmatism can be categorized as simple, compound or of mixed groups. Further sub-classification may result in the condition being viewed as myopic or hyperopic astigmatism.
Symptoms Associated with Astigmatism
Mild astigmatism may not significantly affect vision or health. More severe forms however can cause blurry vision, squinting, fatigue and the development of headaches.
Treating the Condition
Eyeglasses, contact lenses and refractive surgery are means of correcting astigmatism. In modern times, a special type of contact lenses known as toric lenses can correct the condition in many. In some, especially those with severe astigmatism, the use of rigid gas permeable contact lenses may be a preferred option and this enables the attainment of better vision compared to using eyeglasses.
Significant advances in laser eye surgery like that of LASIK surgery is also enabling an increasing variety of astigmatic conditions to be treated successfully.
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