Letters: Multifocal concerns
Author: Dr Greg Williby, David Ruston and Dr Kamlesh
We refer to the article entitled ‘Save the Presbyope: extended depth of focus contact lenses’ published in the contact lens edition of Optician on August 6, 2021 and the interview with Visioneering Technologies’ CEO, Dr Stephen Snowdy, entitled ‘Convincing arguments’ published on September 3, 2021.
We have concerns regarding both, in that the optics and mode of action of leading modern centre near multifocal soft contact lenses (MF SCLs) have not been described correctly. In figure 5 of the first publication these lens designs are described as having three zones, which would render them essentially trifocals. In the interview Dr Snowdy describes them as being a concentric ring design that ‘may contribute to diffraction and diminished performance.’ In reality, most leading MF SCLs have a progressive aspheric design1,2 with a continuous power variation across the optical profile, giving a smooth spread of focus from distance through intermediate to near, with no diffraction occurring, but adding spherical aberration into the optical system.2
Differences between the optical designs of aspheric MF CL products will relate to how much spherical aberration is induced by the design, what orders are used and over what area the optical design is located. Performance will also be influenced by how well the lens centres, how comfortable it is and how well it integrates with the tear film. Practitioners can ‘save the presbyope’ by using the MF SCLs they consider perform best for their patients in these areas.
Dr Greg Williby, principal scientist global platform R&D presbyopia at Johnson & Johnson Vision Care. David Ruston, director global professional education and development, Johnson & Johnson Vision Care. Dr Kamlesh Chauhan, director professional education UK, Ireland, Nordics and DACH at Johnson & Johnson Medical.
- Plainis, S. Atchison, D. Charman, N. Power Profiles of Multifocal Contact Lenses and Their Interpretation. Optom Vis Sci 2013;90(10):1066-1077.
- Kim, E. Bakaraju, R. Ehrmann, K. Power Profiles of Commercial Soft Multifocal Contact Lenses. Optom Vis Sci 2017;94(2):183-196