Monovision contact lens, LASIK and cataract surgical intervention to provide distance and near vision for presbyotic patients may cause previously unidentified depth perception issues that can pose a safety risk.
Presbyopia occurs in our forties when the biological lens in the eye has more trouble changing its shape to accommodate at near. One of the most common treatments for presbyopia is monovision correction, where one eye is treated— either through contact lens wear or surgery— to correct for the best distance vision and the other is to correct at near.
Researchers at the University of Pennsylvania have determined that monovision has given patients a sort of Pulfrich effect, where vision from the eye that has been corrected for near and is blurred at a distance is delayed by the brain by several milliseconds after the fellow eye. This causes the near eye to “think” the objects it is looking at are closer than they really are.
This poses greatest risk while driving when problems with depth perception can cause a serious accident or even while walking down a staircase and miscalculating where the next step should be, causing a fall.
It may be in the best interest of patients, and everyone on the road around them, if they are fitted with either a distance lens to replace the near one for driving or having a designated pair of distance glasses to wear over contacts made for road safety in addition to their monovision correction.
Martinez-Conde, S. (2019, August 9). The illusion of safety. Scientific American. Retrieved from https://blogs.scientificamerican.com/illusion-chasers/the-illusion-of-safety/