What Is Regular Astigmatism of the Cornea?

In order to understand what astigmatism is, and more specifically regular (versus irregular) astigmatism, let’s first get a basic understanding of what astigmatism is in general.
The normal human eye has several structures that are responsible for performing the process of bending and focusing light rays into the back of the eye, namely onto the rear surface called the retina, which in turn creates a clear, focused image which in turn is what we see. Along with the cornea, the lens acts as a prism which gathers that light rays and diverts and concentrates them onto a focal point at the rear of the eye internally.

When one or both of these structures becomes altered from their normal shapes, the ability to focus light in the proper position on the retina inside the rear of the eye becomes compromised, and objects cannot be focused to proper clarity. The process of bending and focusing light in the eye is called refraction. The inability to focus properly because of altered shapes of the cornea, lens or both is called a refractory error. Astigmatism is a refractory error in the eye caused by the inability of the cornea, lens or both to properly bend and focus light rays onto the retina in a manner that produces a sharp clear image, usually by focusing light onto two, rather than one, points on the retina.

There are basically two major types of astigmatism: regular and irregular. Both types produce visual disturbances but do so as a result of their specific and individualized characteristics.
Normally, objects are seen and focused upon in one of two orientations called planes, both vertical and horizontal, and under normal circumstances, the eye is able to do this equally. In regular astigmatism, the different curvatures lie in orientations called meridians and typically lie in 180-degree opposition to each other. This opposition is what causes the ability to focus on the horizontal and not the vertical, or vice versa.

Of the two types of astigmatism, the regular type is the more easily treated and correctable through the use of prescription refractory lenses. This is done by creating curvatures within the corrective lenses that help the cornea gather the light rays and the lens to sharpen and focus the light onto the retina at the back of the eye.

In recent years, technology has progressed to the point where soft contact lenses, called toric lenses, have been manufactured to correct astigmatism. This was for many years largely impossible with the hard lenses.

Regular visits to an eye-care professional can help not only in the diagnosis of astigmatism, as well as other eye problems, but also in the selection of the proper corrective lenses, whether contact or eyeglasses.