Astigmatism is a common refractive error that causes blurred or distorted vision at any distance. It is caused by an imperfectly curved cornea (the clear front surface of the eye) or an irregularly shaped lens inside the eye. Instead of being perfectly spherical, the affected surface is shaped more like a football, preventing light from focusing correctly on the retina. A central question is whether astigmatism can change or worsen significantly as a person ages.
The Typical Lifelong Trajectory of Astigmatism
Astigmatism is often present from birth, and its specific orientation typically follows a predictable course over a lifetime. In younger individuals, astigmatism is most commonly “with-the-rule” (WTR), meaning the vertical meridian of the cornea is steeper than the horizontal meridian. This pattern is generally stable throughout young and middle adulthood.
The shift in astigmatism orientation usually begins around the mid-40s and progresses gradually into later life. The eye slowly moves from the WTR pattern toward an “against-the-rule” (ATR) orientation, where the horizontal meridian becomes steeper. This change in axis, rather than a dramatic increase in the overall magnitude of the error, is the most common age-related alteration.
The actual degree of astigmatism may not increase substantially, but the change in its axis can cause noticeable vision discomfort and blur. This shift often begins after age 40, with the most pronounced changes occurring after the mid-50s. This slow alteration in orientation requires periodic updates to corrective lenses to maintain clear vision.
How Aging Physiology Alters Corneal and Lens Shape
The cornea and the lens, the two main structures responsible for focusing light, undergo distinct physiological changes with normal aging that drive shifts in astigmatism. These biomechanical changes occur naturally over time.
The age-related shift from “with-the-rule” to “against-the-rule” astigmatism is largely attributed to changes in the cornea. Over decades, the constant pressure exerted by the upper and lower eyelids (lid tension) acts to flatten the vertical curvature. This prolonged mechanical stress causes the horizontal meridian to become relatively steeper, leading to the ATR pattern seen in older adults.
The elasticity of the corneal tissue also decreases with age, affecting its ability to maintain its original shape. The lens inside the eye contributes significantly to the total refractive error, and its properties change as it ages and hardens, a process related to presbyopia. This hardening (sclerosis) alters the lens’s internal shape and refractive index, which can induce or change the overall lenticular astigmatism component.
This lenticular change can either partially compensate for or exacerbate the corneal changes, depending on the orientation of the astigmatism it creates. The continuous alteration in the lens’s internal structure contributes to the gradual, measurable changes in a person’s astigmatism prescription over time.
Secondary Astigmatism Changes Caused by Eye Disease
While the slow shift in astigmatism is a normal part of aging, certain eye diseases or acquired conditions can cause a more rapid or significant worsening. Cataract formation represents one of the most common pathological causes of changing astigmatism later in life.
A cataract occurs when the natural lens becomes cloudy and opaque, a process that also involves the lens swelling and changing shape. As the lens matures, its altered curvature can induce a significant degree of astigmatism or dramatically shift the axis of a pre-existing error. This lenticular astigmatism often develops quickly and can be one of the first signs of a maturing cataract.
Changes in astigmatism can also be induced by previous or subsequent eye surgeries. Post-operative changes following cataract removal or glaucoma procedures can alter the tension and curvature of the cornea. Even prior refractive surgeries, like LASIK or PRK, may experience a destabilization of corneal shape decades later due to altered tissue biomechanics, leading to a new or increased level of astigmatism.
Strategies for Monitoring and Correcting Astigmatism Changes
Managing age-related astigmatism changes begins with consistent, comprehensive eye examinations, especially starting around age 40. Regular visits allow the eye care professional to precisely monitor the magnitude and axis of the astigmatism over time. Early detection of a prescription shift ensures that corrective measures are timely and accurate, preventing unnecessary vision strain or blur.
The most common correction methods involve updated prescription eyeglasses or contact lenses, which include specialized toric lenses designed to correct the irregular curvature. For those with significant astigmatism requiring cataract surgery, the condition can often be corrected simultaneously by implanting a toric intraocular lens (IOL). This specialized replacement lens is precisely aligned to neutralize the existing astigmatism.
For individuals who prefer to reduce their dependence on corrective eyewear, enhancement procedures like laser vision correction (LASIK or PRK) can be used to reshape the corneal surface. These surgical options may refine vision after cataract surgery or address astigmatism that has changed significantly due to aging.