Power Profiles of Commercial Multifocal Soft Contact Lenses

Abstract

PurposeTo evaluate the optical power profiles of commercially available soft multifocal contact lenses and compare their optical designs.MethodsThe power profiles of 38 types of multifocal contact lenses—three lenses each—were measured in powers +6D, +3D, +1D, −1D, −3D, and −6D using NIMO TR1504 (Lambda-X, Belgium). All lenses were measured in phosphate buffered saline across 8 mm optic zone diameter. Refractive index of each lens material was measured using CLR 12-70 (Index Instruments, UK), which was used for converting measured power in the medium to in-air radial power profiles.ResultsThree basic types of power profiles were identified: center-near, center-distance, and concentric-zone ring-type designs. For most of the lens types, the relative plus with respect to prescription power was lower than the corresponding spectacle add. For some lens types, the measured power profiles were shifted by up to 1D across the power range relative to their labeled power. Most of the lenses were designed with noticeable amounts of spherical aberration. The sign and magnitude of spherical aberration can either be power dependent or consistent across the power range.ConclusionsPower profiles can vary widely between the different lens types; however, certain similarities were also observed between some of the center-near designs. For the more recently released lens types, there seems to be a trend emerging to reduce the relative plus with respect to prescription power, include negative spherical aberration, and keep the power profiles consistent across the power range.

Changing accommodation behaviour during multifocal soft contact lens wear using auditory biofeedback training

“…The lags at 4 D in the current trial are in a slightly lower range with lags of accommodation of 1.65 D in emmetropic and 1.77 D in myopic participants. Deviations of our results from those reported by Kang and Wildsoet could be explained by the usage of different lens types and addition powers, as they have an impact on the lenses' power profile 36,37 , as well as by applying different measurement devices and conditions (binocular vs. monocular viewing). A reduced accommodation response with multifocal contact lenses causes concern regarding the lenses' efficiency in myopia control: Relaxation of accommodation during near vision would result in more lag (hyperopic defocus) on axis, and possibly even more on the peripheral retina -a condition that might trigger greater axial elongation and myopia progression 38 .…”

“…Furthermore, pupil sizes were continuously recorded in all cases and carefully analysed. They were always above 5 mm, which was larger than the multifocal zones of the contact lenses 36 , excluding the possibility that vignetting could have had an effect. The pupil sizes increased during biofeedback training, assumingly due to arousal, but differences in pupil diameter between the different stages of the experiment were not significant (e.g.…”

Contrast Sensitivity in Emmetropic Presbyopes with Small-Aperture Inlay Implantation: Normative Values and Postoperative Outcomes

“…In comparison, Raindrop inlay implanted corneas are multifocal, similar to central multifocal LASIK [21], with an area of central corneal steepening splitting light energy between near and far and inducing approximately 1 diopter myopic shift along with negative spherical aberration [22]. As shown in simulations, this hydrogel inlay creates a pupil-dependent trade-in image quality in exchange for enhanced depth of focus [23] similar to what has been found with center near multifocal contact lenses [24] thus affects distance vision and photopic distance CS. With this optical design, however, the negative impact on CS may be less evident under mesopic conditions where the pupil enlarges, because distance vision is viewed through the periphery of the cornea, that is, the area of available peripheral distance zone increases with larger pupils and as a result reduces the loss of mesopic distance CS [19].…”

Correction of presbyopia: old problems with old (and new) solutions

“…Multifocality can also be achieved by non‐dynamic methods. Similar to some fish, optical corrections in which optical power varies with spatial location across the pupil have been implemented in modern multifocal IOLs and contact lenses . Radially symmetric or concentric design multifocal lenses are most common, but early multifocal contact lenses employed a segmented geometry inherited from spectacle lenses, as did the earliest bifocal IOL (a variant of which is still produced) .…”

“…Similar to some fish, 15 optical corrections in which optical power varies with spatial location across the pupil have been implemented in modern multifocal IOLs [84][85][86] and contact lenses. [87][88][89][90] Radially symmetric or concentric design multifocal lenses are most common, 20 but early multifocal contact lenses employed a segmented geometry inherited from spectacle lenses, [91][92][93] as did the earliest bifocal IOL (a variant of which is still produced). 94 Segmented bifocal contact lenses, however, suffered from rotational instabilities, 92 and are now typically only implemented as gas-permeable lens designs utilised for a select patient group.…”