Astigmatism is a common refractive error resulting in vision that is blurred or distorted at all distances. It is not a disease, but an imperfection in the eye’s focusing power that prevents light from converging correctly onto the retina. Understanding this condition helps determine if it can resolve naturally and how it can be managed or permanently corrected.
The Mechanism of Astigmatism
Astigmatism occurs because the shape of the eye’s front surface is irregular, causing light rays to bend unevenly. A non-astigmatic eye has a cornea, the clear outer layer, shaped like a perfect sphere. In astigmatism, this surface is curved more like the side of a football, with one meridian steeper than the other.
This irregular curvature prevents the eye from focusing light onto a single point on the retina. Instead, light focuses onto two separate focal lines, creating distorted or blurry vision. The condition can be categorized based on its source: corneal astigmatism, which is the most common, involves the cornea itself.
Less commonly, the irregularity is found in the eye’s natural lens, known as lenticular astigmatism. The lens is located behind the iris and helps fine-tune focusing power. Regardless of the source, the fundamental issue is a rotational asymmetry in the eye’s optics that requires correction.
Does Astigmatism Naturally Change or Resolve?
For most adults, astigmatism does not naturally resolve or disappear on its own once the eye is fully developed. The structural shape of the cornea and lens is generally stable throughout adulthood. Significant spontaneous change in the degree of astigmatism usually signals an underlying issue, such as disease or injury.
Astigmatism can change in severity over time, sometimes increasing or decreasing slightly with age. Notable changes may be caused by conditions like keratoconus, a progressive disorder where the cornea thins and bulges into a cone shape, or as a complication following eye surgery.
In infants, a small degree of astigmatism is common and may lessen as the eye grows and matures during the first few years of life. However, the complete disappearance of established astigmatism in an adult is rare. Correction requires either a temporary optical aid or a procedure that physically alters the eye’s focusing components.
Non-Surgical Correction Methods
Non-surgical methods manage astigmatism by correcting vision without altering the eye’s physical structure. Eyeglasses use lenses ground with a specific cylindrical power to compensate for the irregular curvature. This specialized power counteracts the uneven bending of light, redirecting it to focus on a single point on the retina.
Contact lenses, specifically toric lenses, are another highly effective non-surgical option. Toric lenses have different power zones on the vertical and horizontal axes to match the specific asymmetry of the eye. These lenses require a precise orientation, maintained by design features like weighted bases that prevent rotation with blinking.
These optical solutions provide visual acuity by compensating for the refractive error while worn. They manage the symptom of blurred vision without curing the underlying physical shape of the cornea or lens. Removing the corrective lens restores the original astigmatic vision.
Permanent Surgical Correction
Surgical options permanently correct astigmatism by physically changing the eye’s structure. Laser vision correction procedures, such as Laser-Assisted In Situ Keratomileusis (LASIK), use an excimer laser to precisely reshape the cornea. During LASIK, a thin flap is created in the corneal tissue, and the laser removes underlying tissue to smooth the irregular curvature before the flap is repositioned.
Photorefractive Keratectomy (PRK) is a similar laser procedure, but it involves removing the cornea’s outermost layer (the epithelium) before reshaping the surface. Since no flap is created, PRK is suitable for patients with thinner corneas, though the initial recovery period is longer as the surface layer must regrow. Both LASIK and PRK aim to restore a spherical corneal surface, eliminating the rotational asymmetry causing astigmatism.
For patients with higher prescriptions or other eye considerations, other surgical options exist. Refractive Lens Exchange (RLE) involves removing the natural lens and replacing it with a toric intraocular lens (IOL) that contains the corrective power. Alternatively, an Implantable Collamer Lens (ICL) can be placed inside the eye, in front of the natural lens, to provide permanent correction.