Understanding Astigmatism: Causes, Effects, and Solutions

Astigmatism affects approximately 40 percent of people worldwide, leading to blurred and distorted vision. This refractive error stems from irregularities in the shape of the eye, particularly the cornea, which can disrupt the way light is focused onto the retina. Understanding the causes and potential treatments for astigmatism is crucial for those experiencing vision difficulties.

What Causes Astigmatism?

The eye functions similarly to a camera, where light is captured by the cornea and focused onto the retina at the back of the eye. For clear vision, the eye’s surfaces—including the cornea, lens, and retina—must be properly shaped. When these surfaces are not uniform or smooth, light is scattered rather than focused, resulting in a condition known as refractive error.

Astigmatism can be classified into two main types: regular and irregular. Regular astigmatism is the most prevalent form, often resulting from a cornea that is oval-shaped rather than round, resembling a football. Although the exact reasons for its development are not fully understood, genetic factors play a significant role. Irregular astigmatism, on the other hand, is less common and occurs due to uneven changes in the cornea, often caused by conditions like keratoconus, where the cornea weakens and takes on a cone-like shape.

As light enters the eye through an uneven cornea, it leads to various vision problems, such as double vision, reduced contrast sensitivity, and increased sensitivity to bright lights.

Historical Insights and Measurement

The concept of astigmatism is not new. In 1727, physicist Sir Isaac Newton first described how irregular surfaces could affect light focus. Later, Thomas Young—who also had astigmatism—discussed its effects on vision during a lecture in 1800. By 1825, astronomer Sir George Airy discovered that tilting his glasses improved his sight, leading to the use of cylindrical lenses for correction, a practice that continues today. The term “astigmatism” was coined in 1846 by William Whewell, derived from Greek meaning “without a point,” reflecting the lack of a single focal point in the vision of those affected.

Optometrists typically detect regular astigmatism through a process called refraction, where different lenses are tested to establish a prescription. Irregular astigmatism may require more advanced techniques, such as corneal topography, which produces a three-dimensional map of the cornea to identify irregularities.

Treatment Options for Astigmatism

Astigmatism can present at any age, although its prevalence tends to increase with age. While mild cases may not cause noticeable symptoms, more significant levels can lead to vision distortion, eye strain, and fatigue. Treatment options aim to correct the varying curvatures of the cornea, ensuring light focuses correctly on the retina.

For regular astigmatism, correction is often achieved through cylindrical lenses, which can be prescribed as either glasses or contact lenses. Surgical options, such as laser eye surgery, are also available. Another innovative treatment is orthokeratology (ortho-k), involving the use of specialized hard contact lenses worn overnight to temporarily reshape the cornea, allowing for clear vision during the day without the need for glasses.

Managing irregular astigmatism might require treating the underlying condition causing it. In some cases, hard contact lenses are necessary to provide clear vision, as they can better accommodate uneven patches on the cornea than glasses or soft lenses. Surgical interventions, including corneal transplants, may be considered in severe cases to replace damaged corneas.

Implications for Children

In children, significant astigmatism can hinder learning and development, affecting both classroom performance and participation in sports. While untreated astigmatism is not inherently dangerous, high levels can lead to additional vision problems, such as amblyopia, commonly known as “lazy eye.” Regular eye examinations are essential for early detection and management of astigmatism in both children and adults.

Research from the Centre for Eye Research Australia indicates the importance of understanding and addressing astigmatism. Dr. Flora Hui, a Research Fellow at the Centre, along with Dr. Angelina Duan from the CSIRO, emphasize the necessity of maintaining routine eye checks to ensure timely intervention and to promote better vision health for all ages.