Abstract
Purpose :
To evaluate the in-vitro power profile of a new 3 addition multifocal (MF) contact lens, MyDay® MF (MD, Coopervision, USA) utilising modified monovision to assess the refractive error correction expected with different degrees of presbyopia.
Methods :
MD utilises a pair of low addition lenses (additions ≤+1.25D), low/medium addition combination (additions +1.50D to +1.75D) and low/high addition combination (additions +2.00D to +2.50D) for dominant/non-dominant eyes respectively. The in-vitro power profiles of MD were evaluated for +0.0D, ±1.0D, ±3.0D and ±5.0D in low, medium and high adds (n=2 per power and add, total of 21 power/add combinations) using NIMO TR1504 (Lambda-X, Belgium).
Results :
An example of power profiles of ±3.0D labelled power for each addition are shown in Fig. 1. Low and medium add MD showed similar and progressive power profiles with maximum plus power at centre (Fig. 1A) with the average power change over a 4mm diameter of +0.75D. However, the medium add power profile showed an offset of about +0.50D with low add MD, indicating an over correction of the far point of non-dominant eyes. The high add (non-dominant eye) lens had maximum plus centrally stepping down (Fig. 1B) by an average of +2.4D (+2.2D to +2.7D across power range) over the 2.4mm half chord and also showed significant power change across the peripheral (distance) zone (2.4-3.7mm half chord) both within lens and between powers (e.g. +1.37D and –1.04D for +5.0D and –5.0D, respectively; Table 1). In dominant eyes, the low add lens corrects the far point across all add groups while undercorrecting the intermediate (67 cm) and near (40 cm) points by up to 0.75D and 1.75D (high additions) respectively.
Conclusions :
The MD lens design includes near-centre progressive (low and medium add) and stepped (high add) power profiles. The dominant eye lenses undercorrects the intermediate and near points. The non-dominant eye lenses are adequately powered for near but the change in power in peripheral zone may increase subjective observations such as ghosting and night light disturbance. It is important that clinicians fitting these lenses understand the interocular differences and its effect on binocular vision disparities while performing over refraction.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.