Astigmatism

Q. What is astigmatism?
A. Astigmatism is a focussing error which causes asymptometric blur. Some directions in an image are more out of focus than others. This can be contrasted with shortsightedness (myopia) where all directions are uniformly blurred.

Q. What causes astigmatism?
A. Most astigmatism is caused by the shape of the front surface of the eye (the cornea). It can also be caused by slight tilting of the lens inside the eye. It may be an inherited characteristic or a normal variation accompanying growth.

Q. Can you describe the shape?
A. A magnifying glass focuses the sun to a point image because its two surfaces are spherical, each like the surface of a basketball. Now imagine a transparent surface like that of a football. It has two different curvatures. These result in light focusing at two different locations. The image does not focus to a point and so is blurred.

Q. How does astigmatism affect me?
A. Objects at all distances are indistinct or blurred and the eye cannot focus. Even slight degrees may encourage headaches, fatigue and reduce concentration. This is because the eyes may try, without success, to correct the blur, and because there is a tendency to screw up the eyes to see better, producing discomfort in the muscles of the eyelid and face.

Q. How is astigmatism corrected?
A. All Spectacles and contact lenses (hard and soft) can correct astigmatism. Sometimes correction of astigmatism can cause changes in the apparent size and shape of objects and may affect judgement of distance. A patient may feel taller or shorter, or walls may appear to slope and floors curve. In most cases, adjustment to these side effects takes only a week or so. Astigmatism correction may involve a compromise between optimal clarity and visual discomfort.

Q. How is astigmatism detected?
A. Some people notice blur themselves. Only a proper eye examination will determine for certain if you have astigmatism. Astigmatism is not an eye disease and any changes are generally gradual and not necessarily for the worse. Most people have at least very slight astigmatism.