For glasses to work, they need lenses to alter the path of light entering the eye. Lenses work by putting an image of what you are looking at at an apparent distance from your eye that matches the eyes natural focus. Sometimes, this can actually be behind your head!
These lenses have just one focus, and are the simplest way to compensate for long sightedness, short sightedness or astigmatism. They can also be used for reading glasses. When you are under 40, the eyes natural ability to change focus means that, for most people, single vision lenses are all you need.
bifocals simply means two focuses, so if you need a Â different optical prescription for reading than for driving, both prescriptions are available in the one lens. This becomes a common problem from the mid forties on.
What if you don’t want a line on your glasses? What if you want to see at more than 2 focuses? Then Multifocals , sometimes called progressive addition lenses may be for you. There are no lines on these lenses, and the power gradually increases towards the bottom of the lens.
Lenses may be tinted, have anti glare and/or anti scratch coatings, or even be photochromic (changing colour). We can advise on your best option.