Astigmatism is a refractive error of vision, causing objects to appear blurred. There are several kinds of refractive error. Myopia (shortsightedness) for instance, causes distant objects to be blurry, while hyperopia (farsightedness) affects close objects. Astigmatism gives a blurred image of objects at any distance.
For an object to be seen in focus, light has to be focused on the retina at the back of the eye. The light is first bent by the cornea (the clear membrane at the front of the eye), then further bent by the lens, bringing it to sharp focus on the retina which lines the back wall of the eyeball. The strength of the lens is controlled by the ciliary muscle, enabling the eye to compensate for objects which are at different distances. The ability of the ciliary muscle to change the shape of the lens is the basic mechanism behind focusing the eye.
To achieve a sharp image, the cornea has to be perfectly spherical, the lens has to be uniformly curved, and the eyeball has to be round and the right size. The typical cause of nearsightedness, for instance, is an eyeball which is too long from front the back. Far away objects are focused at a point before the back of the eye, due to its extra depth. Conversely, farsightedness is usually caused by an eyeball which is too short, front to back. Close objects get focused behind the retina.
In astigmatism, the refractive error is caused by the shape of the cornea (corneal astigmatism) or the shape of the lens (lenticular astigmatism). In both cases, the problem occurs because the cornea (or lens) is not uniformly curved. The cornea should be spherical, like a baseball, but in corneal astigmatism it is shaped more like an American football or rugby ball. This means that some light rays will be refracted more than others, giving rise to two points of focus. Some of the light will be focused before the retina, and some will be focused after, resulting in a blurred image.
Many eye exercises are based upon the fact that the eye’s ability to focus is under the control of a muscle, and muscles can be exercised just like any other. Do these exercises improve refractive errors caused by astigmatism? Let’s look at what those exercises are and how they work:
- A typical workout for the eye might involve preliminary washing of the cornea with an eyebath or the hands. Washing dust from the clear membrane would obviously help any optical system, but would not improve the basic astigmatic defect of non-spherical surfaces.
- Resting the eyes periodically to “reset” the light-sensitive cells in the retina is also sensible, but as these are not the cause of refractive errors, there would be little benefit unique to astigmatism.
- Break-taking is a method to exercise the ciliary muscle which controls the focus mechanism of the lens. At regular intervals during close-up work — when the muscle is working hardest — it is advised to look at a distant object for a few seconds. This relaxes the muscle and allows the lens to return to its relaxed shape. While this is effective for lens and muscle health, this will not affect the shape of the cornea and may have no effect upon the basic misshapen form of the lens as seen in astigmatism.
- Eye-squeezes are used to rehydrate the front of the eyes by squeezing them closed to the point of tears. Once again, this is sensible (akin to cleaning the windshield of your car), but would not affect the shape of the eye.
- Massaging the eye sockets and temples with the fingers promotes blood flow to the eyeballs and that brings oxygen and nutrition to the eye. It is most effective in keeping the ciliary muscle supplied with oxygen and with the general health of the retina. Once again these actions would not improve problems specific to the refractive errors of astigmatism.
- The one exercise which might be of benefit in some cases of astigmatism are eye-circles, where you look up, then rotate the eyes clockwise, slowly, up to 10 times. There are some cases of astigmatism caused not by a deformed cornea or lens, but due to the eyeballs being out of shape through bad posture or a continual tilting of the head. The eye deforms to compensate for the altered horizon, resulting in blurring of images at all distances. Eye circles can help to maintain the eyeballs in the state of symmetry required for perfect focusing.
Equalizing the work done by the eye muscles using eye-circle exercises can correct astigmatism caused by distortion of the eye through bad posture. Exercises are, however, unlikely to help in the majority of astigmatism cases.
Originally posted 2016-11-05 05:32:16.