Point by point surfacing for each prescription

Digital surfacing is a major technological advance used in the production of ophthalmic lenses. Most new progressive lenses are machined using this technique.

BBGR reviews the implications of this increasingly dominant trend.

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The rear surface can be produced with complex curves, which will accurately adapt each point of the lens to the patient's visual prescription. With traditional technology, the single rear surface curve is calculated to provide the required power for distant vision.

With digital surfacing, visual performance can be optimised for each point and for each correction, particularly for each cylinder and axis value - and therefore for each direction of view.

Greater freedom with double surfacing.

When the progressive surface is on the front or on the lens' rear surface to be closer to the eye, the other surface is spherical. This means that once the power at each point of the progressive surface has been defined, there remains no further room for manoeuvre.

With digital surfacing, the distribution of different powers between the two surfaces of the lens adds an additional degree of freedom to take advantage of the lens physical parameters (power values, aberrations, prismatic deviations, enlargements, etc.

This makes new and higher performance optical combinations possible, similar to those achieved by optical zooms which use several different lenses to optimise fields and sharpness.

Incorporating new parameters for an individualised solution.

Digital surfacing allows a unique lens to be produced for each individual.

This means being able to avoid any compromise in seeking a single progressive design capable of satisfying the largest number of wearers without, however, being ideal for any one of them.

Patients can now enjoy the advantages offered by lenses entirely adapted to their individual visual needs, which also take into account the frame and the purpose for which they will use them.

This allows refraction data to be complemented by:

  • anatomical parameters (half pupillary distance, eye length, etc.)

  • optometric (accommodation-convergence association type) and psycho-sensorial factors (balance)

We can now take into account the frame and the position of the lens in front of the eye to make sure that the lens' optical function can be preserved in the event of non-standard mounting, or to reduce the progression length so as to allow optimal mounting according to the frame height.

Digital surfacing and lens improvement 

As a technology, digital surfacing is only a means of reaching an end. It does not improve lenses as such. The key to performance remains in creating a design adapted to wearers' needs. The technology is therefore only valid if it is associated with in-depth prior research into an awareness of patients' physiology and the way their needs can be incorporated into the physical characteristics of lens design.

© BBGR UK 2015