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Pete S Kollbaum, Sandra Huenink, Ryan McGiffen, Martin Rickert, Janice Tarrant, Paul Chamberlain; A Best-Eye Model of Binocular Summation with Presbyopic Contact Lens Corrections. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3745.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study was to compare the binocular summation of presbyopic contact lens correction strategies in a subject population requiring a high near add.
Landolt-C (20/100) targets were used to measure the contrast threshold of twenty healthy, non-cyclopleged, high spectacle add (>+2.00D) subjects while wearing monovision (MV)(+0.75 and +2.00D), binocular low and high add multifocal (MF)(lotrafilcon B), and lenses which contain a low level of spherical aberration in each eye combined with +0.75D of monocular defocus in the non-dominant eye (SA+MD)(omafilcon A). Testing occurred in a custom haploscope using custom software at distance, intermediate and near target vergences. A binocular summation ratio (BSR) was calculated as the ratio of monocular performance to binocular performance. Mixed effect models were used to determine the effect of lens type conditioned on eye and viewing distance and the marginal effect of eye within each lens type.
The SA+MD approach provided significantly better binocular distance CS compared to other corrections intended to correct a high add population (i.e MF high (p=0.011), MV+2.00 D (p=0.03)). The same was true for intermediate viewing distances (i.e. MF high (p=0.04), MV+2.00 D (p=0.008)). MV +2.00 D provided significantly better near CS compared to all other corrections (p<0.01), but significantly worse stereoacuity compared to all other corrections (p<0.02). BSR’s did not deviate significantly from 1. Specifically, unlike some previous reports, inhibition (BSR’s below 1) was not observed, even in the presence of large amounts of monocular defocus (i.e. MV +2.00 D).
The SA+MD strategy containing small amounts of spherical aberration in the presence of a small amount of defocus in the non-dominant eye provided good CS at all viewing distances, avoiding potential disadvantages of MV (introduction of larger amounts of monocular defocus) and MF (introduction of larger amounts of binocular aberration). The current data suggest a “best-eye” summation model. Further investigation is warranted to determine the effect of subject task and target stimulus on this result.
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