In an eye with astigmatism, light fails to come to a single focus on the retina to produce clear vision. Instead, multiple focus points occur, in front of the retina or behind it, or both. This causes blurred vision at all distances.
Astigmatism is a type of that occurs when the cornea is irregularly shaped, or in some cases as a result of the curvature of the lens inside the eye. The does not focus light evenly on the retina. The cause of astigmatism is not yet fully understood, but genetics and mechanical interactions between the cornea, eyelids and extraocular muscles may affect its development. Around 90% of the world’s population suffer from some degree of astigmatism.Approximately 50% of individuals worldwide have a degree of astigmatism that can be corrected with corrective lenses.
Astigmatism usually causes vision to be blurred or distorted to some degree at all distances. Symptoms may include squinting to see at all distances, difficulty focusing on printed words, eye strain, tired eyes and headaches.
In addition to the spherical lens power used to correct myopia or hyperopia, astigmatism requires an additional cylinder lens power to correct the difference between the powers of the two principal meridians of the eye.
This describes the lens meridian that contains cylinder power to correct astigmatism. If an eyeglass prescription includes cylinder power, it also must include an axis value. This shows the optician in which direction they must position any cylinder power in your lenses.