Looking at labs: An overview of spectacle lens manufacture

Over the next few months Optician will concentrate on different aspects of the lens manufacturing, and surfacing, process to provide an insight into some of the latest techniques and the equipment involved.

Lens manufacture is essentially a process for shaping, polishing and coating a transparent medium to bend light and change its focal length. The extent to which the light needs to be bent is determined by the prescription measured in practice and the lab uses the details contained within the prescription to create the lens.

All lenses are made from a circular chunk of material known as a semi-finished blank. These are made in volume by lens casters and may be mostly made with a finished front lens or for a few, in an unfinished material.

For simple, low value jobs a semi-finished lens may be cut and edged [shaped to fit the frame] in practice but most practices will use prescription labs for surfaced and more complex, high value work. There are few opticians with the capability to surface semi-finished lenses, but stock single vision finished can be cut to shape in practice.