Astigmatism is a common refractive error where the eye focuses light imperfectly. It occurs when the cornea (the clear front surface) or the lens inside the eye is irregularly curved, shaped more like a football than a sphere. This irregular shape causes incoming light to focus on multiple points rather than a single sharp point on the retina. This results in vision that is blurred or distorted at any distance.
The Typical Trajectory: Stability and Progression
The trajectory of astigmatism progression depends heavily on age. For adults, particularly those in their 20s and 30s, the degree of astigmatism usually remains stable over many years, with minor fluctuations.
Significant changes are common during childhood and adolescence due to rapid eye development. Progression is also expected later in life as a normal part of the aging process, typically increasing slowly over decades.
A rapid or sudden increase in astigmatism, especially in a previously stable young adult, is uncommon and often signals an underlying medical condition affecting the eye’s structure.
Factors That Influence Astigmatism Change
Several specific medical and physiological factors can cause astigmatism to change or significantly worsen over time. One cause of significant progression is keratoconus, a progressive eye disorder. This condition causes the cornea to progressively thin and bulge outward into a cone-like shape, which severely distorts vision and intensifies the irregular curvature.
Changes in the lens inside the eye also play a role, particularly with increasing age. The development of cataracts, where the lens becomes cloudy, can induce or increase astigmatism (lenticular astigmatism) because the altered density and shape of the lens change how light is focused.
Furthermore, as a person ages, the cornea itself undergoes structural shifts, often becoming flatter along the vertical meridian. This change typically causes a shift from “with-the-rule” astigmatism, common in youth, to “against-the-rule” astigmatism in older adults. Eye trauma or complications following certain eye surgeries can also instantly alter the corneal shape, leading to an immediate increase in astigmatism.
Managing and Correcting Changes
When astigmatism worsens, the most common corrective step is updating the prescription for glasses or contact lenses. Toric contact lenses are designed to correct astigmatism by providing different refractive powers to compensate for the irregular shape. For more advanced cases, rigid gas-permeable or scleral lenses may be prescribed, offering a smoother refractive surface over the cornea.
For individuals seeking a long-term solution, refractive surgeries like LASIK or Photorefractive Keratectomy (PRK) can permanently reshape the cornea. These procedures use a laser to correct the corneal curvature causing the refractive error. Patients with cataracts and astigmatism can often address both issues simultaneously with the implantation of a toric intraocular lens during cataract surgery.
If the worsening is due to keratoconus, a specialized procedure called corneal cross-linking may be recommended. This treatment involves applying riboflavin drops and exposing the eye to ultraviolet light to strengthen the collagen fibers in the cornea. This technique aims to halt progressive thinning and bulging, stabilizing the astigmatism.