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

Area of Science:

• Ophthalmology
• Neuroscience
• Developmental Psychology

Background:

• Perceptual learning (PL) shows potential for enhancing near visual acuity (NVA) in children with visual impairment (VI).
• The underlying neural and behavioral mechanisms of PL-induced NVA improvement in children with VI remain largely unexplored.
• Nystagmus, an involuntary eye movement, often co-occurs with VI, potentially complicating visual development and rehabilitation.

Purpose of the Study:

• To investigate the mechanisms by which perceptual learning (PL) improves near visual acuity (NVA) in children with visual impairment (VI) and nystagmus (VI+nys).
• To compare feature search and oculomotor performance between children with VI+nys and normal vision (NV) children.
• To evaluate the effects of different training interventions (experimental PL, control PL, magnifier) on visual performance in children with VI+nys.

Main Methods:

• A feature search task was employed, requiring participants to locate a target 'E' among distractors with varying element spacing (0.04°, 0.5°, 1°, 2°).
• Oculomotor measures, including fixation duration and saccade amplitude, were recorded.
• Children with VI+nys (n=33) underwent 6 weeks of training (experimental PL, control PL, or magnifier), with assessments before and after. Normal vision (NV) children (n=29) were assessed at baseline only.

Main Results:

• At baseline, children with VI+nys exhibited longer search times, shorter fixation durations, and larger saccade amplitudes compared to NV children.
• Following training, all groups showed reduced search times.
• The experimental PL group demonstrated prolonged fixation durations at 0.5° and 2° spacing post-training, which correlated with reduced crowding and improved crowded NVA.

Conclusions:

• Prolonged fixation duration emerges as a potential mechanism contributing to improved crowded NVA following perceptual learning in children with VI and nystagmus.
• Perceptual learning training, specifically the experimental approach, can positively modulate oculomotor behavior (fixation duration) in children with VI+nys.
• These findings highlight the importance of targeting oculomotor control within perceptual learning paradigms to enhance visual function in pediatric populations with visual impairments.