Glare after LASIK surgery includes halos, starbursts, or increased light sensitivity. These are a common, temporary experience for many after the procedure. Understanding why glare occurs provides clarity on this post-surgical effect.
How LASIK Reshapes Vision
LASIK, or Laser-Assisted In Situ Keratomileusis, corrects common vision problems like nearsightedness, farsightedness, and astigmatism. The procedure permanently changes the cornea’s shape, altering how light focuses onto the retina and improving visual acuity.
During LASIK, a thin, hinged flap is created on the cornea’s outermost layer, using a mechanical microkeratome or femtosecond laser. This flap is lifted to expose underlying corneal tissue. An excimer laser precisely removes microscopic tissue, sculpting the cornea into a new curvature. The flap is then repositioned, adhering naturally without stitches, acting as a protective bandage during healing.
Primary Optical Reasons for Glare
Microscopic irregularities on the corneal surface after the procedure can contribute to glare. The flap creation and laser ablation, though precise, can result in a surface that is not perfectly smooth. This unevenness can cause light to scatter rather than focusing cleanly onto the retina, leading to visual disturbances.
A mismatch between pupil size and the treated corneal area is another factor. In low-light conditions, the pupil dilates to allow more light into the eye. If the pupil expands beyond the treated area, light passing through the untreated peripheral cornea can cause glare, halos, and starbursts. Modern lasers aim for larger treatment zones, but this can still occur with larger natural pupil sizes.
Higher-order aberrations (HOAs) are subtle imperfections in the eye’s optical system not fully corrected by standard glasses or contact lenses. LASIK can induce or exacerbate these HOAs, making them more noticeable. They can manifest as glare, halos, starbursts, and reduced contrast sensitivity, particularly in dim light. Changes in corneal shape and asphericity after the procedure can increase HOAs.
Residual refractive error, a small amount of uncorrected vision, can sometimes remain after LASIK. This slight undercorrection or overcorrection can lead to blurry vision or contribute to glare. Over time, subtle changes in corneal shape or surface remodeling can also lead to a return of some refractive error.
Contributing Physiological Factors
Dry eyes are a common side effect after LASIK, contributing to glare. The procedure can temporarily disrupt corneal nerves, reducing tear production and film stability. An unstable tear film can cause light to scatter, exacerbating glare.
Corneal swelling and the healing process also play a role in temporary glare. Immediately after surgery, corneal tissue may be slightly swollen, distorting how light transmits. As the eye heals and swelling subsides, typically within weeks to months, these effects usually diminish. This helps the eye adapt to its new shape.