Glass lenses that are normally clear, but darken in the sunlight, have been available for many years. Plastic lenses, which are lighter in weight than glass, but also change colour, have only been available for the past 5 to 6 years.

Once it was established that plastic lenses, which changed colour, could be made, the race began to make lenses that would go darker, become lighter, and go from light to dark more quickly.

Transition III lenses are the latest design to hit the market. They do all of the above; virtually clear indoors, true grey outdoor tint in the sunlight and change from light to dark and reverse more quickly than any previous design.

These lenses are available in single vision, bifocals, trifocals and multifocals. They are available in hi-index material (thinner,lighter, flatter lenses) and may be supplied with scratch resistant and anti-reflective coatings. For many people Transitions III can do away with the need for a second pair of glasses.