New method for making contact lenses

17 Jun 2002

A small company based in Cambridge, UK, has filed a patent for a new method of manufacturing contact lenses with no aberration and high accuracy with a corresponding improvement in vision.

Contact Lens Precision Laboratories (CLPL) applies mathematical techniques to make a lens which, when worn, is without aberration and accurate to the prescription over almost all of its area. Current lenses are only accurate over 15% of the lens area compared with 95% with the new lens..

CLPL is applying the technology, known as spherical aberration management (SAM), to the prescription lenses it manufactures for opticians and hospitals in the UK. But the company says that SAM is equally applicable to the disposable lenses manufactured by the three major US manufacturers that currently dominate the mass market..

Until now, contact lens manufacturers have worked within specified tolerances, giving an average power correction dependent on the prescribed power and any lens-induced spherical aberrations effects. This prescribed power covers only a small portion of the whole optical zone - in many cases just 1.5 mm despite the fact that the wearer is looking through approximately 5 mm of the centre of the lens. In this case, 91% of the lens optical area is not to the prescribed power..

In a SAM lens, the desired power is constant over the whole of the specified front optic diameter. Typically, this would be 10 mm in a 14 mm diameter soft lens. The usual pupil diameter is in the region of 3.5 mm increasing to about 5 mm in low light. So the accurate portion of the lens is considerably larger than the area the wearer looks through. In addition to improved vision, SAM lenses can also accommodate considrable movement caused by blinking, it is claimed..

The technology has been transferred into a computer numerical controlled program which can be applied on a lens-by-lens basis to all CLPL lenses: mono-focal, multi-focal, soft, rigid, gas permeable, spherical, aspherical, multi-curve and toric..

Keith Lomas, managing director of CLPL, said: "Many wearers and opticians have reported a marked improvement in vision, particularly in low light conditions, where they also find that flaring is eliminated. In one case, a woman who was unable to count her fingers in front of her face has been able to return to work and even regain her driving licence."