Another common complication with standard LASIK, especially when a small optical zone is utilised, is the loss of contrast sensitivity. Visual acuity is a combination of clarity and ability to distinguish contrast. Loss of the ability to distinguish contrast reduces the quality of vision. Vision appears “washed out”, and this is most apparent in dim light.
Similar to night glare and halos, this loss of contrast occurs because of defocused peripheral rays of light entering the outer edge of the pupil. This defocused shattered light blurs the edges of an image and reduces the ability of the eye to distinguish borders. It is this ability to distinguish edges and borders that gives our vision its crispness. Excellent quality of vision is a combination of clarity and crispness.
To correct this loss of contrast an advanced wavefront-guided or PerfectShape® LASIK enhancement is required. For some patients this may not be possible because the residual cornea may be too thin for a repeat laser correction. Fortunately, there is also now a non-surgical therapy available for these patients using NeuroVision™ technology.