Astigmatism is a common vision condition where the eye’s front surface, the cornea, or the lens inside the eye, has an irregular curve. This irregular shape prevents light from focusing evenly onto the retina, leading to blurred or distorted vision. As a type of refractive error, astigmatism affects how the eye bends light and is not considered an eye disease. It often exists alongside other refractive errors, such as nearsightedness or farsightedness.
Measuring Astigmatism
Eye care professionals measure astigmatism using diopters. A perfect eye without astigmatism would have 0 diopters. On an eyeglass or contact lens prescription, astigmatism is indicated by two values: cylinder and axis. The cylinder value, often abbreviated as “CYL,” specifies the amount of lens power needed to correct the astigmatism.
The axis, measured in degrees from 0 to 180, indicates the orientation or location of the astigmatism on the cornea. Think of the eye as a clock face; the axis pinpoints where the curvature is steepest or flattest. For instance, a 90-degree axis runs vertically, while a 180-degree axis runs horizontally across the eye. Both cylinder and axis values are essential for crafting precise corrective lenses.
Classifying Astigmatism Severity
The severity of astigmatism is categorized based on diopter measurements. Mild astigmatism is generally considered less than 1.00 diopter. Many people have a small amount, typically between 0.5 to 0.75 diopters, which often causes no noticeable symptoms or minimal impact on vision clarity.
Moderate astigmatism ranges from 1.00 to 2.00 diopters. Individuals in this range typically experience blurriness or distortion, often warranting corrective lenses for clear vision. Vision may appear blurry at various distances, and some might notice eye strain.
Astigmatism above 2.00 diopters is classified as severe. Some classifications further subdivide this into high astigmatism (2.00 to 4.00 diopters) and extreme astigmatism (above 4.00 diopters). People with severe astigmatism often experience significant blurriness, distortion, and difficulty focusing, impacting both near and distant vision. Achieving 20/20 vision can be challenging even with corrective lenses in such cases.
When Astigmatism Becomes Problematic
Astigmatism becomes problematic when it significantly impacts daily life, regardless of its measured severity. Persistent blurred or distorted vision is a common indicator that correction is needed. This blurriness can affect vision at all distances, making tasks like reading, driving, or recognizing faces difficult. Objects may appear fuzzy or have undefined edges.
Eye strain is another frequent symptom, often resulting from the eyes working harder to compensate for irregular focus. This can manifest as discomfort, aching, or fatigue, particularly after prolonged visual tasks like computer use or reading. Headaches are also commonly reported, caused by the ongoing effort to achieve clear vision. Squinting is a habitual response to improve clarity, but it does not resolve the underlying issue and can contribute to eye strain. Difficulty with night vision, where lights may appear to bounce or have halos, can also signal problematic astigmatism.
The Importance of Correction
Correcting astigmatism, especially when it causes noticeable symptoms or is moderate to severe, significantly improves vision and overall comfort. Proper correction leads to improved clarity and sharpness, reducing blurriness and distortion. This enhances a person’s ability to perform daily tasks with greater ease and confidence.
Leaving astigmatism uncorrected can lead to various issues. Chronic headaches and ongoing eye strain are common consequences, as the eyes and brain continuously struggle to focus. For children, uncorrected astigmatism can pose a risk of amblyopia, also known as “lazy eye,” where vision in one eye does not develop properly. Uncorrected vision problems can also affect performance in school or work, leading to decreased productivity and increased frustration. Consulting an eye care professional ensures proper diagnosis and tailored management, which can include eyeglasses, contact lenses, or surgical options to restore clear vision.