These lenses correct for either Distance or Reading as required, carrying the same power over the whole lens.
These lenses have 2 powers, correcting Distance and Near. The top part of the lens is used for distance and the segment in the bottom half is used for reading/close work. The segment is measured to sit accurately in a particular position. A small line can be seen at the top of the segment. The segment can also come in a few shapes. Bifocals are not particularly common nowadays but are still suitable for some, dependent on lifestyle requirements.
These lenses have no visible line and can therefore be considered more cosmetically appealing than a bifocal. They are progressive lenses that vary in power through the lens. A distance area is at the top of the lens, moving through an intermediate zone and into the near zone. This allows mid range tasks to be addressed i.e. computer screens, dashboard dials etc. There are areas of soft focus towards the periphery of the lenses and the extent of this varies between designs.
THIN & LITE
For those with higher or complex prescriptions, thinner types of lens material are available.
This can keep the lens weight and thickness down considerably which increases comfort for the wearer.
This lens material is clear indoors and reacts outdoors on exposure to UV light. It will then darken down to a sunspec tint, offering variable protection within a single pair of glasses. This can save carrying a separate pair of prescription sunglasses. Once you return indoors the colouration will fade back up to clear. A material more suited for drivers is also now available in a grey coloured option.
A tint will colour the lens to a permanent level of darkness in a shade of your choice. Colours are grey, brown and green and you can select how dark you would wish it to be.
A polarised lens offers even more glare reduction than a tint itself. It cuts light out of the horizontal plane, thus reducing glare. It can be very suitable for driving and fishing in particular, although many people find it generally more comfortable to wear.
A scratch resistant treatment is available which will make the surfaces of your lenses more durable.
An anti-reflection coating reduces glare from problematic artificial light sources such as computer screens, fluorescent lighting, car headlights at night. They also carry an improved cosmetic appearance by offering extra clarity on the lens and being able to see clearly through to the eye, rather than reflective light patches on an uncoated lens.