Astigmatism is a common refractive error where the eye’s cornea or lens has mismatched curves. Instead of being perfectly round, the astigmatic eye resembles a football. This irregular shape causes light to bend unevenly, leading to blurred or distorted vision.
Understanding Astigmatism Severity
Astigmatism is measured in diopters (D), a unit that quantifies the eye’s refractive power. A perfectly spherical eye has 0 diopters. Most individuals have some degree of astigmatism.
Severity is categorized by these values: mild is less than 1.00 D, moderate ranges from 1.00 to 2.00 D, and severe is 2.00 D or more. Higher diopter measurements indicate a more pronounced irregular shape.
Symptoms and Daily Impact
Symptoms vary with severity. Mild astigmatism may cause subtle vision changes, slight blurriness, or no symptoms.
As astigmatism progresses to moderate or severe levels, symptoms become more noticeable. These include blurred or distorted vision at all distances, where straight lines may appear wavy or objects look fuzzy. Other common complaints are eyestrain, headaches, and difficulty with night vision, such as halos or glare around lights. These visual challenges can hinder activities like reading, driving, or computer use.
Can Astigmatism Progress?
For adults, astigmatism typically remains stable, though it can change gradually. Factors leading to progression include natural eye growth, particularly in children.
Aging can also contribute to changes due to alterations in the eye’s lens and cornea. Certain underlying eye conditions may also cause astigmatism to worsen. Any significant or rapid changes in vision or prescription usually warrant further evaluation by an eye care professional.
Extreme Forms of Astigmatism
Astigmatism can manifest in more extreme or irregular forms, significantly impacting vision. One is keratoconus, a progressive eye disease where the cornea, the clear front surface of the eye, thins and bulges into a cone shape. This creates a highly distorted corneal surface, leading to severe, irregular astigmatism.
Unlike common astigmatism, keratoconus-induced irregular astigmatism often cannot be fully corrected with standard eyeglasses or soft contact lenses. Other less common causes include corneal scarring from eye injuries or infections. Complications from eye surgeries, such as corneal transplants or LASIK, can also contribute.
Addressing Severe Astigmatism
When astigmatism is severe or irregular, specialized management options are available to improve vision. Rigid gas permeable (RGP) contact lenses are frequently prescribed because their firm material can create a smooth optical surface, effectively neutralizing corneal irregularities and providing sharper vision. Another effective option, especially for very irregular corneal shapes, is scleral lenses. These larger lenses vault over the entire cornea and rest on the white part of the eye, creating a tear-filled reservoir that helps to smooth out the optical surface.
For conditions like keratoconus, corneal cross-linking is a surgical procedure that can strengthen the corneal tissue and help halt the progression of the bulging. In advanced cases where vision is significantly impaired due to corneal damage or extreme irregularity, a corneal transplant may be considered. Even with severe forms of astigmatism, various strategies exist to manage the condition and enhance a person’s visual clarity and quality of life.