Astigmatism is a very common refractive error where the eye is shaped more like an American football than a baseball, causing light to focus incorrectly on the retina. This irregular shape results in blurred or distorted vision at any distance, not just far away or close up. Astigmatism can occur due to an abnormally shaped cornea, which is the front clear surface of the eye, or an irregularly curved lens located behind the iris. The natural changes that occur in the eye over a lifetime mean that the degree of astigmatism may fluctuate.
Typical Progression and Stability
For most adults, the degree of astigmatism remains relatively stable throughout their mid-adulthood, typically between their late teens and early forties. The eye’s structure is generally mature during this period, and any minor changes are often considered normal refractive drift. However, there are two distinct life stages where changes in astigmatism are commonly observed.
Childhood and Aging Shifts
In early childhood, a high prevalence of astigmatism is common, but it often decreases or stabilizes as the eye develops, a process called emmetropization. Conversely, changes become more noticeable again in older adulthood, usually beginning after age 40. This later shift is often due to the natural aging of the eye’s internal lens, which can change shape and density as it begins to develop cataracts. This lenticular change frequently causes a measurable increase in astigmatism.
The axis of the astigmatism can also shift with age, moving from what is known as “with-the-rule” to “against-the-rule” astigmatism, reflecting changes in the cornea’s curvature. While these age-related changes constitute a worsening in the numerical measurement, they represent a typical, slow progression of the aging process. These predictable shifts are usually slow enough to be corrected easily with updated prescriptions during routine eye examinations.
Underlying Conditions That Cause Significant Worsening
While gradual changes are normal, a sudden or rapid worsening of astigmatism is usually a sign of an underlying corneal disease or trauma. This rapid progression is characterized by the development of “irregular astigmatism,” where the corneal surface has multiple, non-uniform curves, unlike the consistent curvature of regular astigmatism.
Keratoconus
The most common pathological cause of rapidly worsening astigmatism is Keratoconus, a progressive disorder where the cornea thins and bulges outward into a cone shape. Keratoconus manifests in adolescence or early adulthood and progresses over a period of 10 to 20 years, causing significant and irregular corneal distortion. The thinning of the corneal tissue weakens its structural integrity, leading to a measurable, asymmetrical increase in astigmatism that cannot be corrected with standard glasses.
Other causes of irregular astigmatism that can worsen vision include significant eye trauma or corneal scarring from severe infections. Additionally, ectasia, a progressive corneal thinning that can occur years after certain types of refractive surgery, may lead to an unpredictable and severe increase in astigmatism. These severe shifts require prompt diagnosis and specialized management to prevent further vision loss.
Recognizing Symptoms of Change
Recognizing the symptoms of progressing astigmatism is important for seeking timely professional care. The primary indication of a worsening condition is a noticeable decline in visual clarity, even when wearing current corrective lenses. This may manifest as increasingly blurry or distorted vision at all distances.
Symptoms that indicate progression include:
- Frequent or worsening headaches, particularly after periods of concentrated visual work.
- Increased eye strain or fatigue, as the eye muscles work harder to compensate for the focusing error.
- Difficulties with night vision, such as increased glare, halos, or starbursts around lights.
- Needing to squint constantly to achieve a moment of clarity, suggesting the prescription is outdated or the condition has changed.
Management and Correction of Progression
Once progression is confirmed through diagnostic tests like corneal topography, the management approach depends entirely on the cause. For the typical, slow, age-related changes, the solution is straightforward: updating the prescription for glasses or toric contact lenses. Toric lenses are specifically designed with different powers in different meridians to counteract the eye’s irregular shape.
Stabilization Treatments
For cases of significant or rapid worsening, particularly those caused by Keratoconus, the treatment is more intensive and focuses on stabilizing the cornea. The primary intervention to halt the progression of Keratoconus is Corneal Cross-Linking (CXL). This minimally invasive procedure uses riboflavin eye drops and ultraviolet-A light to create new covalent bonds within the corneal collagen fibers, strengthening the tissue and preventing further bulging.
If the cornea is stable but the irregular shape still causes poor vision, specialized contact lenses are often prescribed. Rigid Gas Permeable (RGP) lenses or larger Scleral lenses are used because their rigid structure creates a smooth, artificial surface over the irregular cornea. Regular, comprehensive eye examinations remain the best defense, allowing eye care professionals to monitor changes and intervene with stabilization treatments.