Progressive Power Lenses (PPL), commonly known as ‘Varifocal’ lenses are generally recommended by Optometrists and Dispensing Opticians when you have a two prescription requirement. Typically, one for distance vision and one for near vision.
These lenses are designed in a manner that they have a gradual change incorporated into the strength of the prescription from the top of the lens where the distance portion is set, to the bottom with multiple focal points allowing you to see clearly at all distances through just a single lens.
This effectively means that you don’t need to purchase two pairs of glasses for two different distances.
In comparison to traditional bifocals, they don’t contain a reading segment as such with a visible dividing line. This eliminates ‘Jump’ (difference in sudden magnification between focal lengths) from within the lens which makes them much more functional and cosmetically pleasing. Also, they disguise age very well as onlookers cannot tell the type of lens you’re wearing.
There are 3 portions to a varifocal lens:
Distance Portion: Where the distance component of your prescription is set
Intermediate Portion: The progressive portion between the distance prescription and the
near prescription. Also referred to as the ‘Visual Corridor’.
Near Portion: Where the reading/close up component is set.
Varifocal lenses are generally very easy to adapt to providing that all the measurements pertaining to varifocal lenses are taken correctly during the dispensing process. A full consultation with your optician is imperative in obtaining the right varifocal lens for your use. Varifocal lenses are positioned so that you look through the top portion of the lens to view distance objects. However for reading, you simply lower your gaze to look through the bottom. Also, they have an intermediate power range which is a useful transition between both areas of viewing.
There are numerous different types of varifocal lenses available each offering several features and benefits dependent upon your lifestyle and requirements.
The core differences between them are as follows:
Larger reading viewing areas.
Wider field of vision, known as the ‘visual corridor’.
Less peripheral distortion
In comparison, more advanced lens options provide a wider field of vision with less peripheral distortion (soft focus) hence easier adaptation, comfort and performance.
Occupational/Degressive lenses are widely used terms to refer to varifocal/progressive lenses specifically designed for use in limited work spaces. It generally provides drastically wider visual corridors than traditional varifocal lenses. These categories of lenses are guaranteed to provide very clear vision for the computer and near work, but for distances no further than 4 meters at extreme.
In achieving this level of performance, a compromise had to be made in its design. As a result, the distance field of vision is highly restricted allowing the computer and near regions to be maximised in comfort and clarity.
Generally, a selection of lenses is available offering quality vision at differing working distances. Typically, they are available from 1 metre intermediate settings to 4 metres with a very smooth progression to the near zone over a shorter distance making the transition much more efficient. With increasing demand working within smaller environments, these lenses are becoming ‘first choice’ in delivering a much more enhanced visual experience.
How do they compare?
The majority of patients find that they love the comfort of their varifocal lenses for their day to day living. It gives them immense comfort in all their viewing distances without having to alternate between a second or a third pair in order to view objects at differing distances. However, as working environments have evolved in many fields with increasing use of computers especially, occupational lenses are recommended alongside varifocal lenses at successive eye examinations by optometrist’s and dispensing opticians to enhance visual performance at those particular distances. The aim being, to minimise ocular fatigue and maximise visual performance. As the representation below shows, the intermediate field of view is much wider in an occupational than in the ‘traditional’ Varifocal.