Astigmatism is a common vision condition, categorized as a refractive error, that affects how the eye processes light. It is defined by an imperfectly curved surface of the eye, which prevents light from focusing correctly on the retina. This information is for educational purposes only and is not a substitute for a comprehensive eye examination by a professional.
Symptoms: Take the Self-Assessment
The primary symptom of this refractive error is blurred or distorted vision, which often occurs at all distances, unlike nearsightedness or farsightedness. This can cause objects to appear stretched or fuzzy, with the blurriness sometimes being stronger in one direction, such as horizontally or vertically.
A frequent need to squint to try and clear up the image is a common sign, as the eye attempts to compensate for the irregular focus. This constant effort to adjust vision often leads to secondary symptoms like persistent eyestrain, eye discomfort, and headaches, especially after performing visual tasks.
Difficulty driving or seeing clearly at night is also common. In low-light conditions, the pupil dilates, which can exacerbate the effects of the irregular curvature, causing lights to appear with halos or pronounced glare. If you frequently experience these symptoms, a professional eye evaluation is necessary.
What Causes Astigmatism
Astigmatism is fundamentally caused by an uneven shape in one of the eye’s refractive surfaces. This irregular shape is usually found in the cornea, the clear front surface of the eye, which is known as corneal astigmatism. Less commonly, the lens inside the eye can have the mismatched curves, a condition called lenticular astigmatism.
In a perfectly shaped eye, the cornea and lens work together to refract incoming light rays evenly to meet at a single focal point directly on the retina. When the cornea or lens is curved more steeply in one direction than the other, the light is bent unevenly. This means that instead of a single point of focus, the light forms two separate focal points either in front of or behind the retina.
This inability to focus light rays onto the retina creates distorted or wavy vision. While the exact reason for this irregular shape is often unknown, it is frequently inherited and can be present from birth. Astigmatism can also develop later in life due to eye injury, certain eye diseases like keratoconus, or complications following eye surgery.
Getting a Professional Diagnosis and Treatment
If you suspect symptoms of astigmatism, schedule a comprehensive eye examination with a professional. During this exam, the eye doctor will use specialized tests to measure the degree and axis of the refractive error. Diagnostic tools include retinoscopy, which observes how light is reflected by the retina, and keratometry, which measures the curvature of the cornea.
A more advanced tool, corneal topography, creates a map of the corneal surface. This mapping is valuable as it provides a precise picture of the corneal irregularities, which helps determine the exact prescription needed. These measurements are used to prescribe a personalized corrective solution.
The most common treatment is the use of corrective lenses, either eyeglasses or specialized contact lenses. Eyeglasses contain lenses that are uniquely shaped to compensate for the eye’s uneven curvature. For contact lens wearers, specialized Toric contact lenses are designed with two different power curves to correct the astigmatism and are weighted to prevent rotation on the eye.
Another option is refractive surgery, which uses a laser to permanently reshape the cornea. Procedures like Laser-Assisted In-Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK) alter the corneal curvature to correct the refractive error. These surgical options are considered for moderate to high levels of astigmatism and require a thorough pre-operative assessment to determine candidacy.