The size of an individual's pupil in dim light has been considered a factor in the results of LASIK surgery.
Since the inception of LASIK, there have been a number of factors considered when determining how to deliver superb visual results.
The size of the pupil has been one of those factors.
Due to the introduction of Wavefront driven procedures, doctors are now able to look at all of the components of our eyes that cause blur in vision.
The factors are usually farsightedness, nearsightedness, and astigmatism.
These three factors are usually corrected with contact lenses or eyeglasses.
However, every person has some degree of imperfection in their eyes that cannot be corrected with glasses or contact lenses.
Such aberrations/imperfections are categorized based on their geometric nature and are given fancy names such as coma, trefoil, spherical aberration, etc..
..
Spherical aberration is a type of distortion that can be made worse if the pupil is large.
It can cause a "halo" around lights at night because the pupil is larger in the dark.
This aberration is always increased when a nearsighted person is treated because the central part of the cornea is flattened with the laser.
During the day when pupils are small, the irregularities are covered up as the pupil becomes smaller.
The pupil, being the natural window into the eye, responds to light by reflex causing less light to enter.
It also allows less of the irregularities to be seen by the patient.
In all a smaller pupil is better for the patient, especially in those requiring larger corrections.
Overall, the size of the pupil has an impact on the outcome of the treatment, but it is just one of the factors in delivering results that are satisfactory to the patient.
The pupil size is usually evaluated by the doctor prior to the LASIK procedure.