LASIK (Laser-Assisted In Situ Keratomileusis) is a common surgical procedure used to correct refractive errors like nearsightedness and astigmatism. This procedure uses an excimer laser to precisely reshape the cornea, allowing light to focus sharply onto the retina. While LASIK achieves high success rates for clear daytime vision, patients often express concerns about its effect on vision in low-light conditions. Understanding how the procedure interacts with the eye in the dark is important for setting realistic expectations.
Common Visual Disturbances in Low Light
After LASIK, patients often report specific visual phenomena, collectively known as night glare, which are most noticeable when the pupil dilates in dark environments. Glare occurs when light scatters across the field of vision, making it difficult to see objects near bright sources. This scattering effect can be distracting and reduces contrast sensitivity in dim settings.
Another disturbance is the appearance of halos, which are bright, concentric rings of light surrounding a point source. Halos are caused by the newly shaped corneal surface bending light differently than the untreated cornea. Patients also frequently describe starbursts, which are rays of light that radiate outward from point sources. These visual artifacts are largely temporary and are a normal part of the eye’s adjustment and healing process immediately following the procedure.
The Physiological Causes of Night Vision Changes
The primary reason these visual disturbances occur relates to the difference between the size of the treated area (ablation zone) and the maximum size of the pupil in darkness. LASIK reshapes only a specific central area of the cornea. When the pupil dilates in low light, it may become larger than this treated zone. Light then passes through both the newly shaped central cornea and the uncorrected peripheral cornea, causing light to scatter and resulting in halos and glare.
The reshaping process can also induce or increase subtle imperfections known as higher-order aberrations (HOAs). These are complex optical errors, such as spherical aberration, that are not corrected by standard lenses. The transition zone between the treated and untreated cornea can increase HOAs. This increase becomes visually significant when the pupil is wide open at night, disrupting the precise focusing of light and contributing to starburst and halo effects.
Minimizing Risk with Custom Ablation Technologies
Modern refractive surgery techniques are engineered to mitigate the physiological causes of night vision issues. Advanced methods, such as wavefront-guided and topography-guided LASIK, create a highly personalized map of the eye’s unique optical imperfections before treatment. Wavefront technology measures how light travels through the entire optical system, identifying subtle higher-order aberrations. This detailed mapping allows the laser to create a smoother, optimized ablation profile that minimizes the induction of new HOAs.
Topography-guided LASIK focuses on correcting irregularities directly on the corneal surface. By creating a more uniform surface, these custom procedures effectively reduce the sharp transition zone between the treated and untreated areas. Pre-surgical screening is also crucial, involving the measurement of the patient’s maximum pupil size in low light to ensure the surgeon plans for an appropriately sized optical zone.
Healing Timeline and Options for Persistent Issues
For the majority of patients, night vision disturbances experienced immediately following LASIK are temporary and represent the eye’s natural healing response. The initial appearance of glare and halos is often a result of temporary corneal swelling and inflammation triggered by the surgery. Most individuals notice that these effects gradually resolve or significantly lessen within the first one to three months as the corneal swelling subsides and the tissue stabilizes.
If visual disturbances persist beyond the initial three to six months, they may be due to a residual refractive error or significant induced HOAs. For these rare, persistent issues, non-surgical management options include using anti-glare coatings on glasses for night driving or prescription eye drops to temporarily reduce pupil size. If the issues are severe, a surgical enhancement or re-treatment may be considered. This follow-up procedure often utilizes custom ablation technology to refine the corneal surface and correct remaining imperfections, reducing the source of the night vision problems.