Power profiles in multifocal contact lenses with variable multifocal zone.

BACKGROUND: The power profile of multifocal contact lenses has been demonstrated to report important information that could be used during the fitting process. The aim of this work is to describe the power profile of a recent set of gas permeable multifocal contact lenses as a function of the pupil radius.

METHODS: The measured multifocal contact lenses have a centre-distance design, and are available with five distance-vision diameters (XS, S, M, L and XL) and two different additions: Type A (up to +2.00 D) and Type B (up to +2.50 D). The optical device NIMO TR1504 (Lambda-X, Nivelles, Belgium) was used to obtain the power profile measurements. The optical lens power distribution as a function of the aperture radius was described in terms of radial computed colour maps, radial averaged power profiles, addition, and lens portion used for near vision.

RESULTS: The amount of total addition achieved depends on the diameter of the distance-vision area. That is, the bigger the distance vision area, the bigger the radius of the lens in order to get the same level of addition. In other words, the XS lens provides higher addition values compared to the XL lens design for a given aperture.

CONCLUSIONS: The XS and S designs seem to be aimed to favour near vision, whereas the L and XL designs seem to favour distance vision. For this reason, patients who demand good distance vision might benefit from the L or XL designs, and those with high demand on near-vision tasks might benefit from the XS or S designs. The M design could be the best option for those patients who have the same needs for distance and near vision.