Single vision lenses have the same prescription across the whole surface of the lens and are suitable for driving, reading or other visual needs. Single vision lenses can easily be upgraded to thin and light lenses to greatly improve the appearance of your lens,anti reflective coating to reduce reflections especially night time driving and transitions that change colour in presence of UV light.
If you need glasses for distance and reading then you do have the of seperate pairs which sometimes can be inconvenient therefore you may want to consider bifocals or varifocals
Bifocal lenses have two distinct powers which are seperated by a visible segment at the bottom of the lens. The top part of the lens is for correcting your distant prescription and the segment at the bottom is for correcting your near vision prescription.
Bifocals are generally not useful if you need mid-distance vision i.e. computer work and some people find that the visible segment is not very cosmetically attractive.
Varifocal (also known as multifocals or progressives) are blended lenses which allow you vision at all distances. There’s no visible line like in the bifocal so cosmetically varifocals are more attractive.
However varifocals will not give you 100% clear vision. The lenses are designed so that you have clear vision through a band down the middle of the lens. This means there are areas of soft focus along the edges of the lens. This requires more head movement when you are focusing on objects at different distances which can result in some users describing the feeling as “image swimming”. The key is to be patient and persevere and with time this feeling disappears as your brain adapts.
Depending on the type of varifocal the soft focus can be greatly reduced making it much easier for adaptation.
There are times when ‘standard’ designs are not completely suitable. For instance, Musicians, Pilots, Electricians, Mechanics and Painters and Decorators need to be able to see a close object above their eye-line as well as having normally placed distance and reading vision. There are a range of occupational designs for use under these circumstances. People who work on a VDU screen sometimes need a lens with a much wider intermediate area than normal, and specialist designs are available for this in Multifocal forms.