What is the axis of astigmatism?

The

axis of astigmatism describes the orientation of the eye astigmatism due to the horizontal axis over the center of the eye. It is used for recipes for remedial lenses to indicate the location of correction for astigmatism. This definition of axis of astigmatism refers to regular astigmatism, but irregular astigmatism may have more axis or axis that is not perpendicular, so it is not precisely described by the number of orbit. The normal cornea has a spherical shape, but in the eye with astigmatism is the cornea oval or tied. The elongated shape has steeper curvature in one direction than in the other, causing light to focus differently in the eye with astigmatism. Normally shaped eyes focus light on a single point in the back of the eye, but astigmatic eyes focus on two planes that are perpendicular to each other. The eye tries to focus on the difference of each plane in each plane causes blurred vision. The axis of astigmatism describes this angle using a number between 0 and 180 °. If the axes are vertical and horizontal, both planes are 90 and 180 °. In regularAstigmatism is always separated by 90 °.

There are two aircraft in astigmatism, but the regulation axis is only one number, so there must be a way to recognize which plane the axis number refers to. This is done by determining the difference between the two planes. The power is measured in diopters and indicates the required strength of correction. The prescription that corrects for astigmatism contains procedure correction for myopia or foresight, but also the power marked cylry or cylinder. Powering the cylinder is the difference in force between two planes of astigmatism.

The

axis of astigmatism indicates an angle of plane with lower power. In the example of the planes at 90 and 180 °, if the plane has 180 ° lower power, then the axis of astigmatism is 180. On the contrary, if the plane has a lower power, the axis is 90.