Purchase this article with an account.
Fabian Conrad, Ravi C Bakaraju, Indrani Perera, Eon Kim, Klaus Ehrmann, Brien A Holden; Comparison of single vision, bifocal and multifocal contact lens power profiles obtained using two high resolution power mapping instruments. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4670.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To characterise the optical power profiles of a range of commercially available soft contact lenses using two different measurement principles and thereby aiding in understanding and improving clinical performance of these lenses.
Seven commercially available contact lenses (AirOptix® AQUA Multifocal HI [AOMF], ACUVUE® Bifocal [AB], Proclear® Multifocal “D” design Add+2.5 [PCMF], CLARITI® 1 Day Multifocal Add High [CMF], PureVision multifocal Add High [PVMF], MiSight® [MS] and AirOptix® AQUA Single Vision [AOSV]) were measured (powers -3.00D and -6.00D, 2 lenses of each power) using two advanced power mapping instruments (NIMO Lambda-X and Phase Focus Lens Profiler). Custom software, performing radial averaging and ray-tracing, was used to convert thickness data output by the Lens Profiler into radial power profiles.
Substantial differences in the distribution of power over the optic zone of the measured lenses were found. AOSV lenses showed a smooth, approximately linear and flat power profile. The power of AOMF lenses decreased uniformly starting at the lens centre, reaching the nominal (labelled) distance power approximately at the 2 mm half-chord. All other lenses showed a distinct non-uniform pattern of power changes. AB and MS lenses had concentric rings of relative positive power with abrupt transitions between zones whereas transitions in other multifocal lenses were smoother with approximately linear or stepped gradients between zones. Power profiles obtained by the two methods were in very close agreement with deviations generally being less than 0.25D.
These measurements illustrate different optical approaches taken by manufacturers to incorporate relative positive power (typically to achieve enhanced depth of focus and thereby reading addition) into soft contact lenses. The level of agreement between the two instruments suggests that data, at least for the lenses measured here, can be used interchangeably. When compared to AOSV lenses, all lenses showed zones of relative plus power within the optic zone. Detailed knowledge of the distribution and rates of power change between zones aids in understanding differences in clinical performance between these products.
This PDF is available to Subscribers Only