Astigmatism is a common condition where the eye has an irregularly shaped cornea or lens, causing light to focus unevenly onto the retina. This refractive error results in blurred, distorted, or hazy vision at any distance. The question of whether this condition inevitably worsens with age is a frequent concern for those who have it. While the eye’s structure changes throughout a person’s life, these changes do not always lead to a simple “worsening” of the condition.
Understanding the Two Primary Types of Astigmatism
Astigmatism is primarily categorized by the specific part of the eye that is irregularly shaped: the cornea or the crystalline lens. Corneal astigmatism, which is the more common type, occurs when the clear, dome-shaped front surface of the eye is shaped more like a football than a perfect sphere. Lenticular astigmatism, in contrast, results from an irregularity in the shape or position of the eye’s internal crystalline lens.
The total refractive error experienced by an individual is a combination of both corneal and lenticular components. The magnitudes and axes of these two components do not always align; in some cases, the lenticular astigmatism may actually partially counteract the corneal astigmatism, leading to a lower total prescription.
How Astigmatism Changes During Adulthood and Senescence
The trajectory of astigmatism throughout a person’s life is not static, but it follows a generally predictable pattern. For most individuals, astigmatism remains relatively stable during young adulthood, typically through their 20s and 30s. A notable shift occurs as people enter their middle and later years, particularly after age 40.
While the overall prevalence of astigmatism increases in older age groups, the type of astigmatism commonly observed changes. Most young people present with “with-the-rule” astigmatism, where the vertical meridian of the eye is the steepest curvature.
As aging progresses, the axis of the astigmatism tends to shift, moving toward “against-the-rule” astigmatism, where the horizontal meridian becomes the steepest curve. This transition is a hallmark of senescent change, resulting in a different blur pattern and requiring adjustments to corrective lenses. The magnitude of the astigmatism may not necessarily increase drastically, but the change in axis is a common finding in older adults.
Age-Related Physiological Drivers of Change
The primary forces driving the changes in astigmatism with age are the natural, gradual alterations occurring within the eye. The crystalline lens, located just behind the iris, is the most dynamic component contributing to these shifts. Throughout life, the lens continuously grows new layers, making it thicker and less flexible, which leads to presbyopia.
This thickening and hardening of the lens, along with changes in its internal refractive index, directly affects the lenticular astigmatism. These lenticular changes often work to neutralize or compensate for the pre-existing corneal astigmatism, which is why the overall magnitude may not increase significantly in some cases. Additionally, the tension and position of the eyelids and the structure of the corneal collagen fibers can subtly alter the shape of the cornea over decades.
A significant physiological driver in older adults is the development of cataracts, which is the clouding of the crystalline lens. As a cataract forms, it can induce or worsen lenticular astigmatism, often causing a noticeable and sometimes rapid change in the prescription. This progression is distinct from the more gradual shift in the astigmatism axis caused by the subtle mechanical and structural changes of normal aging.
Pathological and External Factors Causing Progression
While normal aging causes predictable shifts in astigmatism, significant and rapid worsening is typically a sign of a secondary issue or external influence. One of the most common pathological causes is Keratoconus, a progressive eye disorder where the cornea thins and bulges outward into a cone shape. Keratoconus can cause a substantial and fast increase in astigmatism, often leading to irregular astigmatism that is difficult to correct with standard glasses.
External factors, such as trauma or eye injury, can also instantly alter the shape of the cornea, causing new or worsened astigmatism due to scarring. Repetitive, vigorous eye rubbing, often associated with allergies, is a mechanical stress that can contribute to the development or progression of Keratoconus over time.
Astigmatism can also be a consequence of eye surgery, such as following cataract extraction or a corneal graft. Surgical incisions can temporarily or permanently change the tension and curvature of the cornea, which may induce a new astigmatic error. Therefore, a sudden, marked change in astigmatism is usually an indicator that a specific disease process or external event, rather than just the passage of time, is affecting the eye’s structure.