Astigmatism is caused by abnormalities in the shape of the globe, cornea, or lens of the eye, which creates a refractive error. Astigmatism presents with changes in visual acuity, sensitivity to light, and brightness of contrast. The age of onset of astigmatism varies. For some it is present at birth, for others it presents in childhood or early adulthood.

Astigmatism can be classified as:

  • Corneal astigmatism
  • Lenticular astigmatism
  • Total astigmatism

What Causes Astigmatism?

While it is clear that distortions in the structure of some of the components of the eye are associated with astigmatism, the pathomechanism by which these occur is not yet clear. 

Risk factors of astigmatism include:

  • Genetics
  • Ethnicity- It is more common in East Asians and Native Americans
  • Pterygium
  • Surgical procedures of the eye
  • Trauma to the eye
  • Eye diseases, such as keratoconus

Those with astigmatism are also more likely to be diagnosed with hyperopia or myopia.

Source: Mohammadi, S. F., Khorrami-Nejad, M., & Hamidirad, M. (2019). <p>Posterior corneal astigmatism: a review article</p> Clinical Optometry, Volume 11, 85–96.