Astigmatism is a common condition where the eye’s front surface, the cornea, or the internal lens has an irregular, non-spherical curvature. This irregularity prevents light from focusing correctly onto the retina, resulting in blurred or distorted vision at any distance. While astigmatism is often present from birth, its degree can change over a person’s lifetime, sometimes worsening. Understanding how to recognize the signs of this progression is important for maintaining clear vision and overall eye health.
Subjective Symptoms of Worsening Astigmatism
The most immediate sign that astigmatism may be progressing is a noticeable increase in the severity of existing visual discomfort. Objects that previously appeared only slightly distorted may now seem stretched or significantly blurred, affecting both near and far vision. This blurring might feel constant, unlike the blurriness of simple nearsightedness or farsightedness which is typically limited to specific distances.
Intensified eye strain and fatigue often accompany this increased blurring as the eye muscles work harder in an attempt to compensate for the focusing error. Patients may also experience a corresponding increase in the frequency or severity of headaches, particularly those localized around the eyes or forehead after periods of visual concentration.
Difficulty with night vision is another prominent symptom that usually worsens when astigmatism progresses. As the pupil dilates in low-light conditions, it allows more light to enter the irregularly shaped cornea, magnifying the focusing errors. This results in increased glare, halos, or starbursts appearing around light sources like streetlights and oncoming headlights, making night driving particularly challenging.
Underlying Causes of Astigmatism Progression
The measurable increase in astigmatism can be attributed to several factors, ranging from normal physiological changes to underlying disease processes. One common reason for gradual change is the natural aging of the eye, which can affect the shape and flexibility of both the cornea and the internal lens. Over time, the lens may lose elasticity and become less flexible, contributing to a change in the overall refractive error.
A gradual shift in prescription is often seen during childhood and adolescence as the eye grows, and later in life due to changes in the lens. While this slow progression is often mild, a more significant or rapid increase in astigmatism can signal a more serious underlying condition. The most important of these is keratoconus, a progressive disorder where the cornea thins and bulges outward into a cone shape.
Keratoconus is a pathological cause of irregular astigmatism that typically begins in the teenage years or early adulthood and can progress quickly. Frequent and vigorous eye rubbing, often linked to allergic conditions, is a mechanical stressor that can exacerbate the condition. A high level of astigmatism, particularly 2.00 diopters or more, is strongly associated with an increased likelihood of this corneal thinning disorder.
Objective Measurement by Eye Care Professionals
While a patient’s symptoms offer subjective evidence of progression, eye care professionals rely on specific objective tests to accurately quantify and confirm any worsening of astigmatism. The standard method for updating a vision prescription is the refraction test, which determines the precise cylindrical power and axis needed to achieve the sharpest vision. This test measures the refractive error and provides the definitive number that tracks the degree of progression in diopters.
Corneal topography is a specialized, non-invasive procedure that provides a detailed, colored map of the cornea’s surface curvature. This mapping is particularly useful because it identifies irregularities and pinpoints exactly where the steepest and flattest meridians of the astigmatism lie. By comparing current and previous topographical maps, a doctor can detect subtle changes in corneal shape that confirm progression, especially if the astigmatism has become irregular, which is a hallmark of conditions like keratoconus.
Another procedure sometimes used is pachymetry, which measures the thickness of the cornea. Since conditions that cause significant astigmatism progression often involve corneal thinning, pachymetry provides objective data to monitor the structural integrity of the eye. Together, these precise measurements confirm the amount of change and help the doctor differentiate between a minor refractive shift and a more concerning structural change.
Deciding When to Seek Medical Attention
While routine annual or biennial eye examinations are the best practice for monitoring stable astigmatism, certain changes necessitate an immediate visit to an eye care professional. Any sudden or rapid change in vision, such as a noticeable increase in blurriness over a period of weeks or months, should prompt an unscheduled appointment. This rapid progression can be a sign of an active disease process that requires timely intervention.
Seeking care is appropriate if the subjective symptoms begin to significantly interfere with daily activities, such as reading, working on a computer, or safely operating a vehicle, especially at night. If new symptoms like persistent, intense eye pain or a significant increase in light sensitivity accompany the blurring, professional evaluation is warranted.