What Happens in Case of Visual Blurriness?

Clear vision is not only comfortable: it provides the brain with fixed references (fovea) and a precise optical flow (periphery) essential for postural control and motor guidance.

When the image becomes blurred — uncorrected myopia, fog, accommodative fatigue, or removal of glasses — the sensorimotor loop loses one of its columns of information and must be reconfigured.

Loss of Foveal Anchor

The fovea detects micro-shifts of the body in relation to a fixed point. Blurring the target ↑ sway: +40% in young people, ×2 in vestibular-deficient individuals (Rohellec 2004).

The brain then shifts towards the periphery, vestibule, and proprioception, which are less precise at low amplitudes.

Noisy Optical Flow

Blurriness dilutes contours; the periphery struggles to estimate speed/direction. Result: "noisy" signal, delayed corrections (+20 ms) and exaggerated → stiffer posture (Schubert & Minor 2014).

Compensation Strategy and Fatigue

Deprived of reliable reference, the system ↑ co-contraction of extensors: +15% energy in prolonged standing (Paillard 2017).

In motor terms, precision ↓: in table tennis, blurriness ±1 diopter → doubles placement error and ↓ striking speed (Purves 2019).

Dynamic Effects

Walking: no shorter steps, cadence ↑ (“hammer blow”). Turns: widened base; in seniors, insufficient adaptation → risk of falling (Schubert & Minor 2014).

Practical Solutions

• Quick optical correction (glasses, contact lenses, anti-fog).
• Vestibular and proprioceptive training.
• Contrasted peripheral exercises (patterned balls, optokinetics).

In Summary

Visual blurriness disorganizes sensory hierarchy: delayed corrections, increased rigidity, increased expenditure, decreased precision. Restoring clarity or strengthening other channels is essential.

References

1. Paillard T. (2017). Plasticity of the postural function to sport and/or motor experience.
2. Purves D., et al. (2019). Neuroscience (6th ed.). Oxford University Press.
3. Rohellec J-L. (2004). Vision and Sport. INSEP.
4. Schubert M. C., & Minor L. B. (2014). Optokinetic stimulation and postural control. In Vestibular Rehabilitation (4th ed.).