Simulator for Twilight and Night Vision
after LASIK or LASEK
LASIK is an excellent procedure for the correction of mild to moderate nearsightedness and for mild farsightedness. Your vision at dawn, dusk and at night stays the same as prior to LASIK. However, LASIK is subject to certain limitations, which result from the severity of the existing nearsightedness or farsightedness in conjunction with the diameter of the pupil. When the nearsightedness or farsightedness is very severe and when the pupil is very dilated, halos (rings of light surrounding a light source) may occur at dawn, dusk and at night, which may result in decreased vision.
A halo occurs because of an imbalance between the size of the corneal zone treated with Excimer laser ablation and the diameter of the pupil when dilated at night. If the diameter of the dilated pupil exceeds the diameter of the "ablated" corneal zone, a halo is perceived when part of the light rays coming into the eye produce a blurry image.
FreeVis has developed a vision simulator that demonstrates twilight and night vision for both nearsightedness and farsightedness. The simulator takes into consideration your refractive error and the diameter of your pupil when dilated in darkness. Be aware that no simulator can provide a precise image for each individual because human vision is very adaptable. We generally get used to halos and eventually stop perceiving them. The simulator shows that in mild to moderate cases of nearsightedness or farsightedness, no change in vision is perceived. However, for people with more severe nersightedness it demonstrates how halos may influence twilight and night vision.
Consult your surgeon prior to treatment to determine whether you can expect any limitations in twilight and night vision.