Immediate cortical adaptation in visual and non‐visual areas functions induced by monovision

Abstract

A common and often successful option to correct presbyopia with contact lenses is monovision. This is an unbalanced correction across the two eyes where one eye is corrected for far vision and the other eye is corrected for near vision. Monovision is therefore a form of acquired anisometropia that causes a superimposition of an in-focus image with a blurred image. In spite of this visual anisometropia, monovision has been successfully used for many decadesl however the brain mechanism supporting monovision is not well understood. The present study aimed to measure the visual evoked potentials with a high-density electrode array (64-channel) in a group of presbyopes and to provide a detailed spatiotemporal analysis of the cortical activity after a short period of adaptation to monovision with contact lenses. When compared with a balanced eye near correction, monovision produced both a clear reduction of the earliest visual evoked potential components, the C1 and the N1, and an amplitude increase of the P1 and pP1. These results indicate that the unilateral blurring induced by wearing monovision contact lenses reduces feed-forward activity in the primary visual area and feedback activity in extrastriate areas (C1 and N1 reduction). Interestingly, other brain activities in both extrastriate visual areas (the P1 component) and in the anterior insula (the pP1 component) appear to compensate for this dysfunction, increasing their activity during monovision. These changes confirm the presence of fluid brain adaptation in visual and non-visual areas during monocular interferences.

Electrophysiological evidence of sustained spatial attention effects over anterior cortex: Possible contribution of the anterior insula

“…We observed larger amplitudes in the attended compared to the unattended condition for both pN1 and pP1 peaks, which can reflect higher salience associated with attended stimuli. This interpretation is also supported by a recent study about the effects of induced ocular anisotropy (monovision) on ERPs (Zeri, Berchicci, Naroo, Pitzalis, & Di Russo, ).…”

“…Insular localization and independence of anterior components from posterior extrastriate activity has been confirmed in the current study using two separate and converging source analyses (eLORETA and BESA), as found in other ERP studies using sLORETA and BESA source localization methods (Perri, Berchicci, Bianco, Quinzi, et al, ; Perri, Berchicci, Bianco, Spinelli, et al, ). In addition, dissociated effects on prefrontal (pN1 and pP1) and occipital (P1 and N1) components demonstrate the independency of these components—for example, stimulus visibility reduced the occipital components but increased the prefrontal components (Perri, Berchicci, Bianco, Quinzi, et al, ; Perri, Berchicci, Bianco, Spinelli, et al, ; Zeri et al, ).…”

Presbyopia: Effectiveness of correction strategies

“…Presbyopia definition Some definitions of presbyopia purely focus on near visual loss, but do not relate this to a visual requirement (Moshirfar et al, 2017;Zeri et al, 2018); hence many young visually impaired individuals could be considered presbyopic with such definitions. However, other definitions are more functional such as "Presbyopia is a condition of age rather than ageing and as such is devolved from the lamentable situation where the normal age-related reduction in amplitude of accommodation reaches a point when the clarity of vision at near cannot be sustained for long enough to satisfy an individual's requirements" (Gilmartin, 1995) or Millodot in his Dictionary of Optometry and Visual Science who defines presbyopia as "A refractive condition in which the accommodative ability of the eye is insufficient for near vision work, due to ageing" (Millodot, 2007).…”

Presbyopia monovision correction and cortical adaptation

“…The article ‘Immediate cortical adaption in visual and non‐visual areas functions induced by monovision’ in this issue of The Journal of Physiology approaches adaptation to monovision with contact lenses, one way of compensating the loss of near vision that affects all humans with ageing (Zeri et al . ).…”

“…Consequently, the hypo‐functioning of the primary visual cortex did not negatively affect the visual perception due to the contribution of other visual and non‐visual areas, which increased their activity to compensate a reduced sensorial input, still ensuring effective vision (Zeri et al . ).…”