Training shortens search times in children with visual impairment accompanied by nystagmus.

Bianca Huurneman,F Nienke Boonstra

doi:10.3389/fpsyg.2014.00988

Abstract

Perceptual learning (PL) can improve near visual acuity (NVA) in 4–9 year old children with visual impairment (VI). However, the mechanisms underlying improved NVA are unknown. The present study compares feature search and oculomotor measures in 4–9 year old children with VI accompanied by nystagmus (VI+nys [n = 33]) and children with normal vision (NV [n = 29]). Children in the VI+nys group were divided into three training groups: an experimental PL group, a control PL group, and a magnifier group. They were seen before (baseline) and after 6 weeks of training. Children with NV were only seen at baseline. The feature search task entailed finding a target E among distractor E's (pointing right) with element spacing varied in four steps: 0.04°, 0.5°, 1°, and 2°. At baseline, children with VI+nys showed longer search times, shorter fixation durations, and larger saccade amplitudes than children with NV. After training, all training groups showed shorter search times. Only the experimental PL group showed prolonged fixation duration after training at 0.5° and 2° spacing, p's respectively 0.033 and 0.021. Prolonged fixation duration was associated with reduced crowding and improved crowded NVA. One of the mechanisms underlying improved crowded NVA after PL in children with VI+nys seems to be prolonged fixation duration.

Highlights

Evidence is accumulating that perceptual learning (PL) can have a beneficial impact on a range of visual perceptual skills, from contrast sensitivity (Polat et al, 2009) to visual acuity (Hussain et al, 2012) and depth perception (Uka et al, 2012)
We recently demonstrated that PL induces specific learning effects on the trained task in children with visual impairment (VI), and transfers to improvements in near visual acuity (NVA) (Huurneman et al, 2013)
Valid oculomotor measures were collected in 20 children with normal vision (NV), and 24 children with VI accompanied by nystagmus (VI+nys)

Summary

Introduction

Evidence is accumulating that perceptual learning (PL) can have a beneficial impact on a range of visual perceptual skills, from contrast sensitivity (Polat et al, 2009) to visual acuity (Hussain et al, 2012) and depth perception (Uka et al, 2012). Fiorentini rightfully questioned: “Where does this learning occur?” A review on the neural basis of PL reported that training has no effect on, or only weakly alters, sensitivity of neurons in early visual areas, but instead constitutes to long-term changes in high level decision making stages that read out sensory signals (Kumano and Uka, 2013). We recently demonstrated that PL induces specific learning effects on the trained task in children with visual impairment (VI), and transfers to improvements in near visual acuity (NVA) (Huurneman et al, 2013). An important question is whether NVA improvements and reduced crowding ratios after PL are related to oculomotor changes in children with nystagmus. The present study investigates the influence of PL on feature search performance and oculomotor measures

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