Nighttime can transform familiar visual scenes into confusing distortions. These visual disturbances, especially around light sources, are often frustrating and impact daily activities like driving. Astigmatism, a condition affecting the eye’s shape, is a common underlying cause.
Understanding Astigmatism
Astigmatism is a common refractive error, affecting how the eye bends light. Instead of a perfectly round curvature like a basketball, the cornea (clear front surface) or the lens has an irregular, football-like shape. This uneven curvature prevents light rays from focusing precisely on a single point on the retina, the light-sensitive tissue at the back of the eye. Vision can then appear blurry or distorted at all distances. Astigmatism can be present from birth, inherited, or develop later due to eye injury or disease.
Common Night Vision Disturbances
Nighttime often brings specific, bothersome visual phenomena for individuals with astigmatism. One frequent experience is seeing halos, which appear as bright rings or circles around light sources like streetlights or headlights. These halos arise because the irregularly shaped cornea or lens scatters incoming light rather than focusing it cleanly. Alongside halos, people with astigmatism commonly report seeing starbursts, where streaks or rays radiate outwards from lights. This effect also results from light being split and distorted as it passes through the eye’s uneven surface.
Glare is another prevalent issue, manifesting as excessive brightness from light sources, which can be disorienting and uncomfortable. This heightened sensitivity to bright lights can make tasks such as night driving challenging and potentially hazardous. Beyond these specific light effects, general blurring or smearing of light sources is also common, making it difficult to discern clear outlines of objects in low-light environments. The severity of these disturbances can vary depending on the degree and type of astigmatism a person has.
Why Nighttime Worsens Astigmatism Effects
The visual challenges posed by astigmatism become more pronounced in low-light conditions due to the eye’s pupil. In dim environments, the pupil, the opening controlling light entry, dilates or widens. This dilation allows more light to enter the eye, which is beneficial for seeing in the dark.
However, when the pupil expands, it exposes a larger area of the cornea and lens, including more peripheral regions that might have greater curvature irregularities. Light rays passing through these irregular outer parts are refracted unevenly, leading to increased distortion. The result is an exacerbation of symptoms like halos, starbursts, and glare, making them more noticeable and impactful than in brighter conditions when the pupil is constricted.
Managing Astigmatism for Better Night Vision
Addressing astigmatism is achieved through professional eye care. A comprehensive eye examination is crucial for diagnosis, involving tests like visual acuity assessment, refraction to measure how light bends, and keratometry to assess corneal curvature. These evaluations help determine the precise nature and extent of the astigmatism.
Correcting astigmatism and improving night vision often involves corrective lenses. Eyeglasses with specific cylindrical prescriptions can compensate for the eye’s irregular shape. Toric contact lenses are designed with varying refractive powers to align with the unique curvature of an astigmatic eye, providing clear vision. For those seeking a more permanent solution, refractive surgeries like LASIK (Laser-Assisted In Situ Keratomileusis) and PRK (Photorefractive Keratectomy) reshape the cornea using lasers to correct the refractive error. These procedures aim to reduce or eliminate the need for glasses or contact lenses, improving night vision by creating a more uniform corneal surface. Consulting with an eye care professional is the first step to determine the most suitable management strategy.