Astigmatism is a common condition where the eye’s shape prevents light from focusing correctly on the retina, leading to blurred vision. This refractive error typically occurs when the cornea, the clear front surface of the eye, or the lens inside the eye, has an imperfect, football-like curvature instead of a perfectly round one. This uneven shape causes light to bend unevenly, affecting vision at various distances.
Common Visual Symptoms
Individuals with astigmatism often experience blurry or distorted vision across all distances, whether looking at nearby objects or those far away. This can make it difficult to discern fine details, such as reading small print or recognizing distant road signs. Many people report seeing glare or halos around lights, particularly during nighttime driving, which can be disorienting.
The constant effort to achieve clear focus can lead to symptoms like eye strain and discomfort. Headaches are also a frequent complaint, especially after prolonged visual tasks like reading or using digital screens. Some individuals may instinctively squint to sharpen their vision. These symptoms can vary greatly in intensity, and some people with mild astigmatism might not notice any visual disturbances.
Why Self-Diagnosis Isn’t Possible
Despite experiencing noticeable symptoms, self-diagnosing astigmatism is not reliable. The visual disturbances associated with astigmatism, such as blurry vision or eye strain, can also indicate other refractive errors like nearsightedness (myopia) or farsightedness (hyperopia), or entirely different eye conditions.
While some online or at-home tests may offer a preliminary indication, these are not substitutes for a professional evaluation. Accurately measuring the precise curvature of the eye’s components requires specialized diagnostic equipment. Only a comprehensive eye examination by a qualified eye care professional can differentiate astigmatism from other conditions and determine its exact type and degree.
How Eye Care Professionals Diagnose It
An eye care professional, such as an optometrist or ophthalmologist, employs a series of specific tests during a comprehensive eye exam to diagnose astigmatism. One initial step is the visual acuity test, where a patient reads letters from a chart at a set distance to assess overall vision sharpness. This provides a baseline understanding of how clearly a person can see.
Further objective measurements involve instruments like the keratometer, which precisely measures the cornea’s curvature by projecting a light and analyzing its reflection. Another objective method is retinoscopy, where the practitioner shines a light into the eye and observes the light reflection from the retina to determine the refractive error. This test is particularly useful for patients who may have difficulty providing verbal feedback, such as young children.
Automated devices called autorefractors also provide an objective estimate of the eye’s refractive error, including astigmatism, by measuring how light reflects off the retina. These measurements offer a starting point for the prescription. The subjective refraction test is then performed using a phoropter, a device with various lenses, allowing the patient to look through different lens combinations and indicate which provides the clearest vision. For more detailed analysis, especially in complex cases, corneal topography may be used to create a comprehensive map of the cornea’s surface.
When to Schedule an Eye Exam
It is advisable to schedule an eye exam if you experience persistent blurry or distorted vision, frequent eye strain, recurring headaches, or difficulties with night vision. Any sudden or gradual changes in your visual clarity warrant a professional assessment.
Routine eye examinations are also important for both adults and children, even in the absence of obvious symptoms. Astigmatism can sometimes develop gradually or be present without noticeable signs, especially in children who may not recognize their vision is not typical. Early diagnosis allows for timely and effective correction, often with eyeglasses or contact lenses, which can significantly improve visual comfort and clarity.