Monovision Monovision is a fitting technique where the contact lens in the dominant eye is used for distance viewing and the other, non-dominant eye is set for a near focal distance. The concept works well for people who do not use both eyes simultaneously and who t herefore lack stereoscopic binocular vision. For those with normal stereo vision, monovision could cause a potentially significant loss of depth perception. There is some controv ersy among eye doctors as to whether forcing the brain to make this adjustment is really such a good idea. The loss of stereoscopic depth perception could put the wearer at risk of misjudging distances.
Many practitioners recommend against the use of mono vision while operating a motor vehicle.
Another concern is the appropriateness of altering brain function for a cosmetic benefit, especially when considering that there are alternatives that provide good visual acuity while preserving binocular vision. Instead of a dedicated near vision contact lens in the non-dominant eye, a multifocal lens is used. This preserves st ereopsis and depth perception at distance to a significant degree in most cases. A lens can be considered for extended wear if the gas permeability exceed s a certain threshold. Current thinking is that for most people three or four days is the maximum continuous wearing time that allows for reasonably normal corneal physiology.