Astigmatism

With astigmatism images blur or objects you look at are distorted. In ordinary far- and near-sight the eye refracts all light rays with the same degree of error, in astigmatism the error varies in different planes. Typically the cornea have the greatest refractive power at the vertical meridian The 12 o’clock, 6 o’clock line of the watch dial. This is known as with-the-rule astigmatism or direct astigmatism. This is by far the most common type of astigmatism, about 88% of all cases.

The less common against-the-rule astigmatism occurs when the refractive power of the cornea is greater along the horizontal meridian, or the 9 o’clock – 3 o’clock line on the watch. About 5% of all cases are against-the-rule astigmatism. Indeed, it is possible to have astigmatism at any point of the compass and it is also possible to have horizontal as well as oblique astigmatism.

The conventional explanation is that the fault is inherent in the eyeball – either in the cornea or the entire eyeball is supposed to be congenitally distorted. Ophthalmologists define astigmatism as generally caused by toroidal anterior corneal surface.

Hofsteller and Rife (1953) concluded that astigmatism was mostly an environmentally determined trait. Lyle (1965) believed that no hereditary patterns was discernable for astigmatism under 2 diopters.

In other words astigmatism is an irregularity in the curvature of the cornea caused by tension and pressure on the eyeball. In rare instances, astigmatism forms in the lens or the retina.

Optometrists correct astigmatism by introducing a cylinder lens element. The combination of spherical and cylindrical elements forms a complex curved shape, somewhat like the sections of a football.

Many people have the misconception that astigmatism is an actual disease which it is not. There are people who can spontaneously generate up to 3 diopters of astigmatism. Contrary to traditional belief, astigmatism is very fluid and easy to correct. Relaxation is the key to correcting astigmatism.