Astigmatism is a common imperfection in the curvature of the eye’s front surface (the cornea or the lens), causing light to focus unevenly on the retina. This refractive error results in blurred or distorted vision at any distance, similar to looking through a wavy glass pane. The stability of astigmatism depends heavily on a person’s age and the presence of any underlying eye health conditions.
Stability Versus Lifespan Changes
For most healthy adults, astigmatism tends to remain stable throughout their middle years after the eye has fully developed. While minor fluctuations can occur during routine checkups, a significant or rapid change is not expected in the absence of disease. In children and adolescents, however, changes are common as the eye grows and refines its shape. This developmental period frequently sees a reduction in astigmatism as the eye matures.
The trajectory of astigmatism shifts again later in life due to the natural aging process of the eye. In younger individuals, the cornea tends to steepen along the vertical axis, a pattern known as “with-the-rule” astigmatism. Over time, changes in the cornea’s structure cause the horizontal meridian to become steeper. This gradual shift leads to the development of “against-the-rule” astigmatism, which is common after age 60.
This age-related alteration in corneal shape causes a measurable change in the overall refractive error, often requiring an update to a person’s prescription. This change is distinct from a sudden pathological worsening. The type of astigmatism often changes predictably across a lifespan, even if the magnitude does not always worsen.
Underlying Causes of Progression
While slow changes are normal, astigmatism can significantly worsen due to specific disease states or external factors. One concerning cause is corneal ectasia, a group of progressive disorders where the cornea thins and weakens. The most common form is Keratoconus, where the central cornea bulges outward into a cone shape due to a loss of structural integrity. This shape change rapidly increases the degree of astigmatism, making it irregular and difficult to correct with standard glasses or contact lenses.
Chronic eye rubbing is a risk factor that contributes to the progression of Keratoconus, particularly in genetically predisposed individuals. The formation of a cataract, the clouding of the eye’s natural lens, can also induce or change astigmatism. As the internal lens hardens and swells with age, its altered thickness and curvature shift the prescription toward nearsightedness. This lens-induced astigmatism only stabilizes once the cataract is surgically removed.
Astigmatism can also be altered by ocular surgery, particularly procedures that involve incisions into the cornea. For example, cataract surgery or corneal transplants can induce a temporary or permanent change in the cornea’s shape as the tissue heals. Even modern refractive surgeries, such as LASIK, involve reshaping the cornea to correct astigmatism. However, the healing process can sometimes result in a residual or induced refractive error.
Identifying Significant Changes
A worsening of astigmatism often presents with noticeable symptoms that prompt an eye examination. Individuals may report increased blurriness, particularly if vision is distorted into streaks or shadows. Frequent headaches, persistent eye strain, and the need to squint are common complaints associated with progressing astigmatism. These symptoms are often more pronounced when driving at night or looking at bright points of light, which can appear smeared or starburst-like.
When a person reports these changes, a clinician confirms the progression during a comprehensive eye exam. The degree of astigmatism is measured using a phoropter or automated refractor to determine the necessary lens power. To understand why the astigmatism is changing, clinicians rely on corneal topography. This specialized instrument maps the exact curvature and elevation of the corneal surface, creating a detailed color-coded image.
Monitoring the topography map over multiple visits allows the eye care professional to detect subtle changes in corneal shape. This is important for catching progressive conditions like Keratoconus early. Regular annual or biennial eye examinations are the most effective way to monitor the stability of the condition and ensure changes are addressed promptly.