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From the 2nd Ophthalmology Department, Aristotle University of Thessaloniki, Papageorgiou General Hospital, Thessaloniki, Greece (KTT, SAD, ITT); Institute of Vision and Optics, School of Health Sciences, University of Crete, Crete, Greece (SP); and Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom (SP).
The authors have no financial or proprietary interest in the materials presented herein.
Several surgical procedures can potentially satisfy the needs of the presbyope by counteracting the effects of reduced amplitude of accommodation in the aging eye. These are based on three principal approaches: (1) monovision,1 which uses the capacity of the brain to process the focused retinal image from one eye, (2) accommodative IOLs,2 which target to recover true accommodation by producing ocular/lens power changes, and (3) simultaneous vision (image) correction (ie, an increase in the ocular depth of focus) through lens multifocality, which can provide functional distance and near vision for every visual task.3,4 Simultaneous image correction achieved with diffractive IOL designs (offering a bifocal effect) or multifocal/refractive designs (offering a smooth transition in power between distance and near corrections) has significantly reduced spectacle dependence.5,6
One phenomenon that may play an important role in the success of the simultaneous-image designs to aid presbyopes is neural adaptation.7 The idea that patients can, over time, adapt to their somewhat blurred retinal images so that their visual performance improves with time is not new. Previous studies have referred to this,8,9 but comparatively few studies have attempted to explore its characteristics. An interesting issue is the role of binocular integration on such forms of plasticity. It is well established that vision with two eyes is enhanced over what would be expected with just one eye10 when conditions of binocular overlap and fusion are achieved. This phenomenon, called "binocular summation," is mainly attributed to the existence of neurons in the visual cortex that "summate" the signals from the two eyes.11 Interestingly, a recent study12 has shown that binocular vision ameliorates the effect of blur.
Unexpectedly, although most of the aspects of visual performance with IOLs have been thoroughly studied, there are no reports regarding the amount of gain in visual acuity as a result of binocular vision. The aim of the current study was to investigate the effect of binocularity on visual performance...