Assessment & Research

Vertical saccades in dyslexic children.

Tiadi et al. (2014) · Research in developmental disabilities 2014
★ The Verdict

Dyslexic readers show measurably slower and less accurate vertical eye movements—consider visual tracking demands when designing reading interventions.

✓ Read this if BCBAs who teach reading to late-elementary kids with dyslexia.
✗ Skip if Clinicians working only with preschool or non-reading goals.

01Research in Context

01

What this study did

The team watched how dyslexic and typical kids move their eyes up and down.

Each child sat in front of a screen and followed a dot that jumped vertically.

Cameras tracked eye speed, delay, and accuracy while kids did nothing but look.

02

What they found

Dyslexic readers took longer to start each eye jump and often jumped too soon.

Their eyes also moved more slowly and landed short of the target.

Looking up took even longer than looking down, a pattern not seen in controls.

03

How this fits with other research

Bellocchi et al. (2013) already summarized that dyslexic eyes wander; this study gives the hard numbers for vertical moves.

Razuk et al. (2018) then showed that a simple green sheet of plastic can shorten eye fixations and speed reading.

Hattier et al. (2011) found the same kids wobble more when standing still, hinting that weak visual-motor links show up in many body parts.

Together the four papers draw one line: dyslexia is not just a sound problem; it is also a "where do I look" problem that you can partly fix.

04

Why it matters

If a child stalls on flashcards or loses her place, test vertical tracking before you blame phonics.

Add quick eye-warm-ups: have the child follow your finger up and down five times, then read.

You can also try a green overlay; Milena’s team saw faster reading with one.

These tiny tweaks cost nothing and may spare minutes of escape behavior each session.

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Start each reading trial with five vertical finger-tracking sweeps to warm up the eyes.

02At a glance

Intervention
not applicable
Design
quasi experimental
Sample size
112
Population
other, neurotypical
Finding
negative

03Original abstract

Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering.

Research in developmental disabilities, 2014 · doi:10.1016/j.ridd.2014.07.057