The term many people search for as “stigmatism” is medically known as astigmatism, a common vision problem caused by an imperfect curvature of the eye. This condition is classified as a refractive error, meaning it affects how the eye bends light to create a clear image. Astigmatism prevents light from focusing evenly onto the retina, the light-sensitive tissue at the back of the eye. Instead of a single, sharp point of focus, light is spread out, resulting in unclear vision.
Understanding Astigmatism: The Physical Cause
Astigmatism occurs when the cornea (front surface of the eye) or the lens has an uneven shape. In an eye with perfect vision, the cornea and lens are spherical, allowing light to focus at one precise point on the retina. When astigmatism is present, the curvature is irregular, often described as being shaped like a football rather than a basketball. This irregular curvature causes light rays to bend more in one direction than another. As a result, the light focuses on multiple points instead of a single point, creating distorted vision. The condition is often present at birth and can occur alone or in combination with nearsightedness or farsightedness.
Visual Symptoms and Impact
The most noticeable effect of astigmatism is blurred or distorted vision, affecting both close-up and far-away objects. This distortion may make straight lines appear wavy or tilted. The eye attempts to compensate for this uneven focus, leading to secondary symptoms. Common complaints include eye strain, discomfort, and headaches, particularly after periods of intense visual concentration like reading or looking at a screen. Astigmatism can also severely impact night vision, causing lights to appear with pronounced glare, halos, or starburst effects.
Correction and Treatment Options
Astigmatism is highly treatable through several methods that aim to neutralize the eye’s irregular curvature. The most common treatment involves corrective lenses, such as eyeglasses or contact lenses.
Corrective Lenses
Eyeglasses use a specific type of lens to counterbalance the eye’s irregular shape. These lenses have different powers in different meridians, or axes, to properly bend light and achieve a single focal point on the retina.
Contact lenses designed to correct astigmatism are called toric lenses. Unlike standard spherical contacts, toric lenses are shaped with a specific orientation and weighted mechanism to ensure they stay in the correct position on the eye and provide the necessary correction.
Refractive Surgery
For a more permanent solution, refractive surgery is an option. Procedures like Laser-Assisted In Situ Keratomileusis (LASIK) use a specialized laser to precisely reshape the cornea, making its curvature more uniform and spherical.
Photorefractive Keratectomy (PRK) is another surgical option that also reshapes the cornea but involves removing the outer layer for laser treatment. These procedures smooth the corneal curve, which often reduces or eliminates the need for glasses or contact lenses.