Astigmatism is a common vision condition caused by an imperfection in the eye’s curvature, affecting either the cornea or the lens. Unlike a perfectly spherical eye, an astigmatic eye is shaped more like an American football. This irregular shape prevents light from focusing precisely on the retina, leading to blurred or distorted vision at various distances. While present throughout the day, astigmatism becomes particularly noticeable and challenging in low-light or nighttime conditions.
Nighttime Visual Manifestations
In dark environments, astigmatism significantly alters how lights appear, creating distracting visual phenomena. Individuals commonly experience halos, bright circles or rings surrounding light sources like streetlights or car headlights. Another frequent manifestation is starbursts, where lights radiate outward with spikes or rays. Lights may also appear fuzzy, streaky, or generally blurred.
This distortion makes it difficult to discern details and judge distances accurately, especially while driving at night. Oncoming headlights might stretch, appear hazy, or even seem to double, making navigation challenging. This visual impairment often leads to increased squinting, causing eye strain and discomfort. These effects highlight why uncorrected astigmatism poses specific challenges for nighttime activities.
Factors Worsening Night Vision
Astigmatism’s effects are amplified at night due to the eye’s pupil. In low-light, the pupil dilates, or widens, allowing more light to enter. This larger opening permits more peripheral light rays to pass through the irregularly shaped cornea or lens.
An astigmatic eye scatters light instead of focusing it precisely on the retina. The influx of additional light through a dilated pupil exacerbates this scattering. This increased scattered light makes optical aberrations—halos, starbursts, and streaks—more pronounced against the dark background. The stark contrast between bright light sources and surrounding darkness intensifies these distortions, making even mild astigmatism a significant issue after sunset.
Strategies for Nighttime Vision Improvement
Several strategies can help manage astigmatism’s nighttime visual effects, with corrective lenses being the most common solution. Prescription eyeglasses or contact lenses, specifically toric lenses, compensate for the eye’s irregular curvature. Toric lenses feature different powers to correct the astigmatism’s specific orientation, ensuring light focuses properly on the retina. Anti-reflective (AR) coatings on eyeglasses can also reduce glare and reflections, improving clarity.
For a long-term solution, refractive surgeries like LASIK or PRK can reshape the cornea to correct astigmatism. Modern LASIK procedures, including wavefront-guided or topography-guided treatments, can enhance night vision by addressing complex optical imperfections. Beyond medical interventions, practical measures also aid nighttime vision, such as ensuring car windshields, mirrors, and headlights are clean. Adjusting rearview mirrors to their night setting, dimming dashboard lights, and avoiding direct stares into oncoming headlights can minimize glare and reduce intense visual disturbances.