These are trade names for Photochromic lenses that change from clear lenses into
Transitions or Reactolites go darker with sunlight and then clear up once the person
goes indoors - works on basis of UV in the air that causes chemical reactions within
the lens. The light reactive lenses can go dark in winter if it has been snowing
due to increased UV being reflected off the snow.
Tip - a car windscreen tends to block UV and so usually do not work in a car - so
best to use prescription sunglasses if driving in sunny conditions
Whether you wear glasses or not, it is important to wear sunglasses to protect your
eyes from harmful UV from the sun. The UV can cause eye conditions such as earlier
onset of cataracts, macular degeneration and premature aging of the skin round the
Alsosunglasses cut down on glare to improve vision and to reduce eyestrain.
Polaroid lenses reduce glare by filtering out the horizontal part of it - bit like
Been popular in fishing as reduces glare from surface of water and helps to see the
fish a lot better ! Also ideal for driving to reduce glare from car bonnet and flat
Tip - can reduce LCD image as these can be pre-polarised eg cash machines and in
some car displays. Avoid polaroid lenses for downhill ski slopes as could miss seeing
These lenses are made from a higher density material that can produce the same power
but with a thinner lens. Called high index lenses or thinner lenses.
These may be recommended for higher prescriptions, because the standard lenses tend
to be thicker than for low powers.
They improve cosmetic appearance and usually come with anti glare coatings as standard.
Material of lenses-glass, plastic and polycarbonate.
Each have advantages and disadvantages
Glass lenses - thinner and more scratch resistant but are heavier and can shatter
on an impact.
Plastic lenses - lighter and do not shatter. Therefore more safer and first choice
of lenses. They can be thicker than glass and scratch more So coatings are advised
( see below )
Polycarbonate lenses are more impact resistant and so mainly used for safety eyewear.
Scratch more easily than plastic.
Useful for plastic lenses as they can scratch more easily then glass lenses. However
the coating wont make lenses scratch proof - just more resistant.
Tip - put either the spectacles in the glasses case or rest specs with its arms on
the surface of a table than its lenses touching it. Clean the lenses wet than dry
- as cloth can drag dirt or grit on lens surface.
Reduces glare from computer screens and car headlights. Helps to improve vision by
allowing more direct light through. Also improves cosmetic appearance - as onlooker
can see the persons eye better - instead of reflections. Also called anti reflective
Ideal for computer users and for night driving.
Would recommend if choosing designer frames or with high prescriptions as it does
give an improved look.
Tip - The anti reflective coating normally comes as standard with thinner lenses
along with a scratch resistant coating. Therefore may be more cost effective to have
thinned lenses in higher prescriptions. Called hi-index lenses.
Onlooker may notice a blue or green tinge to the lenses instead of white light reflection
but the user does not see this in their own vision.