What are the causes of astigmatism?

From the Guidelines

Astigmatism is primarily caused by an irregularly shaped cornea or lens in the eye, with the most common cause being corneal astigmatism, as stated in the refractive errors preferred practice pattern 1. The cornea, which is normally spherical, becomes more oval-shaped in people with astigmatism, preventing light from focusing properly on the retina and resulting in blurred or distorted vision. Several factors contribute to astigmatism development, including:

• Genetics, as astigmatism often runs in families
• Congenital astigmatism, where people are born with the condition
• Eye injuries, surgeries, or certain eye diseases like keratoconus, which causes the cornea to thin and bulge
• Constant pressure on the cornea, such as from frequently rubbing the eyes or wearing poorly fitted contact lenses
• Age-related changes to the lens, which can sometimes cause or worsen astigmatism It's worth noting that reading in poor light or sitting too close to screens does not cause astigmatism, as stated in the example answer. Fortunately, astigmatism can be effectively corrected with glasses, contact lenses, or in some cases, refractive surgery like LASIK, as mentioned in the refractive surgery preferred practice pattern 1. Additionally, corneal ectasia, particularly keratoconus, can also lead to irregular astigmatism, as discussed in the corneal ectasia preferred practice patterns 1. However, the most recent and highest quality study on the topic, the refractive errors preferred practice pattern 1, provides the most comprehensive overview of the causes of astigmatism.

Some key points to consider when evaluating the causes of astigmatism include:

• The role of genetics and family history in the development of astigmatism
• The potential for eye injuries, surgeries, or certain eye diseases to contribute to astigmatism
• The impact of constant pressure on the cornea, such as from eye rubbing or poorly fitted contact lenses
• The relationship between age-related changes to the lens and the development or worsening of astigmatism
• The importance of early identification and treatment of corneal ectasia, such as keratoconus, to prevent or slow the progression of irregular astigmatism.

Overall, a thorough understanding of the causes of astigmatism is essential for providing effective treatment and management of the condition, and for improving patient outcomes and quality of life.

From the Research

Causes of Astigmatism

The causes of astigmatism can be categorized into several types, including:

• Congenital astigmatism, which is present at birth 2
• Contact lens induced astigmatism, which can occur due to the use of certain types of contact lenses 3
• Surgically induced astigmatism, which can occur as a result of refractive surgery 2
• Irregular astigmatism, which can be caused by corneal surgery, trauma, dystrophies, and infections 4
• Internal refractive surface and media irregularity or noncorneal astigmatism, which can contribute to irregular astigmatism of the entire refractive path 4

Factors Contributing to Astigmatism

Several factors can contribute to the development of astigmatism, including:

• Alterations in corneal curvature, which can occur with age 5
• Genetic factors, which may play a role in the development of astigmatism 5, 6
• Corneal thinning disorders, such as keratoconus, which can cause astigmatism due to the progressive thinning of the cornea 6
• Eyelid position and tension, which can influence the shape of the cornea 5
• Corneal stromal collagen fibrils, Descemet membrane, and extraocular muscles, which can also influence the shape of the cornea 5