Purpose : The Through Focus Curve (TFC) is often used to characterise visual performance of multifocal contact lenses (MCL) and intra ocular lenses over a range of defocus. Typically negative lenses are used to produce vergences but this requires accurate lens centration and trial lenses may interfere with binocularity. The objective was to characterize a new MCL using a new clinical test paradigm, measuring visual acuity (VA) at the actual distances of interest, allowing normal convergence and both binocular and monocular measurements.
Methods : Monocular, binocular (B) and binocular summation (BS) TFCs were obtained by measuring logMAR VA at 6 distances (40cm, 50cm, 67cm, 1m, 2m & 4m) for 3 luminances (250cd/m2 daytime and computer use, 50cd/m2 indoor evening & 2.5cd/m2 night driving). The measurements were made with OTG-i Vision using a 4K screen at distance, an iPad 2 Air (retina) for intermediate and an iPad mini (retina) for near, all driven by a dedicated App. The study MCL was 1-DAY ACUVUE® MOIST Brand MULTIFOCAL. The study population (age 51.7 ± 7.37) comprised 7 low, 10 medium and 13 high addition subjects.
(i) Mean BVA at 250cd/m2 was < 0.0 logMAR (>20.20) at
all distances. The best BVA was achieved at 2m (-0.19 logMAR 20/13) and
the lowest at 40cm (-0.04 logMAR 20/18);
(ii) Mean BVA at 50cd/m2 was lower than at 250cd/m2 by 1 line at distance (+0.1 logMAR), 1.2 lines at intermediate (+0.12 logMAR) and 1.4 lines at near (+0.14 logMAR) maintaining a balanced performance for all distances;
(iii) Mean BVA at 2.5cd/m2 was biased for distance, with 2.5 lines (0.25 logMAR) loss compared with 250cd/m2 giving a mean VA of 20/25;
(iv) Differences in VA between dominant and non-dominant eyes were small, at most 1/3 of a line (mean differences -0.025 to + 0.029 logMAR); with a trend to favour the dominant eye at distance and the non-dominant eye at near;
(v) BS was most marked at distance (mean -0.01 to -0.04 logMAR), demonstrating that the MCL were not biased towards modified monovision maintaining binocularity.
Conclusions : This novel “real world” clinical technique was able to fully characterise the TFC performance of the study MCL, demonstrating excellent performance at high luminance while maintaining balanced VA at all distances at medium luminance and a bias towards distance at low luminance (night driving). In addition monocular and binocular VA measurements have confirmed binocular summation with the MCL.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.