Power Profiles of Multifocal Contact Lenses and Their Interpretation

Abstract

The variation in power across the simultaneous-image lenses produces enhanced depth of focus. The through-focus nature of the image, which influences the "best focus" (distance correction) and the reading addition, will vary with several factors, including lens centration, the wearer's pupil diameter, and ocular aberrations, particularly spherical aberration; visual performance with some designs may show greater sensitivity to these factors.

Power profiles of single vision and multifocal soft contact lenses

“…As found in measurements taken by the SHSOphthalmic, power data within the central 0.6 mm of the optic zone were not reliable, which the authors attributed to dirt or defects at the lens centre. Comparing Plainis' results with this investigation, there is general agreement in the power profiles, although some of the particular addition power values may differ by up to 0.95 D [23]. The two different measurement principles, Hartmann-Shack technique versus ptychographic imaging might result in the detected discrepancies, but more significantly, the different definitions of near and distance powers would have generated different numerical values.…”

“…A similar metrological study has recently been conducted by Plainis and colleagues [23] who evaluated power profiles of four multifocal soft contact lens types in low, medium, and high addition power using the Phase Focus Lens Profiler. However, only plano lenses were investigated, allowing no assessment of spherical aberration.…”

“…Very recently, Plainis et al [23] evaluated the Phase Focus Lens Profiler (Phase Focus Ltd., Sheffield, UK) and compiled power profiles of four multifocal soft contact lens types. The instrument measures thickness maps of the complete contact lens, which can then be converted into Dk/t or power maps.…”

“…The instrument measures thickness maps of the complete contact lens, which can then be converted into Dk/t or power maps. The power maps can be derived with a mean spherical power repeatability of 0.02 D. Thickness measurements are obtained by scanning a laser beam over the sample and combining the captured diffraction patterns produced by the scattered light to reconstruct the thickness map [23,24].…”

Repeatability of in vitro power profile measurements for multifocal contact lenses

“…Papas et al [7] evaluated the refractive power within the optical zone with a contact lens power analyser. Plainis et al [8], measured the power profile of several multifocal contact lenses with a lens profiler based on ptychographic imaging. And Wagner et al [1] investigated the power profile of single vision and multifocal contact lenses with a wavefront sensing instrument.…”