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Lens geometry
Geometry describes how the surfaces of a lens are designed and how the optical power is distributed across the different zones. It is one of the reasons why two lenses made to the same prescription can offer different visual experiences.
The prescription is only part of the picture
Sphere, cylinder, axis and addition describe the prescribed correction; lens geometry determines how that correction is arranged across the lens. This affects the width of usable zones, peripheral performance, thickness, curvature and scope for customisation.
Spherical, aspherical and free-form
An aspheric lens uses surfaces of varying curvature to create a flatter profile and better manage some optical trade-offs than a conventional spherical design. With free-form lenses, the surface can be calculated and worked point by point, using the prescription and, where relevant to the design, individual parameters and how the glasses will be worn.
Progressive, office and single-vision lenses
In progressive lenses and office lenses, the design arranges zones for different viewing distances and the transitions between them. Even a single-vision lens can have a more or less advanced design. The prescription alone therefore does not tell you whether two lenses are the same product.
The Isolani technical project
The chosen geometry has to suit the frame, its dimensions and angles, and how the glasses are actually worn. Behavioural Centring captures those parameters; the Isolani workshop completes the fitting and final checks. Our guide to ophthalmic lenses explains how we combine international technology with local expertise.
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