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New research · Ophthalmology
Investigative ophthalmology & visual science · 1d
StudyInvestigative ophthalmology & visual science · 2026

Development of Crowding Distance in Children Is Faster and Later Than Visual Acuity and Better Predicts Reading Performance.

Sarah J Waugh, Monika A Formankiewicz, Leticia Álvaro, Denis G Pelli
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OphthalmologyStudy

Crowding distance correlates more strongly with children's reading ability than visual acuity does.

Development of Crowding Distance in Children Is Faster and Later Than Visual Acuity and Better Predicts Reading Performance.

Sarah J Waugh … Denis G Pelli
Investigative ophthalmology & visual science · 2026
Purpose

Visual crowding is a failure of object recognition due to nearby clutter.

Methods

Visual acuity (isolated Sloan letter size threshold) and crowding distance (Pelli optotype spacing threshold) were measured in 227 normal, healthy children aged three to 11 years and 40 adults.

n = 40 adults
Results

children with worse crowding tended to have weaker reading skills

CD-trigram
-0.68r
CD-repeated
-0.67r
VA
-0.37r
More results

From age three years, visual acuity improves 1.4×, reaching near-adult levels at six years (P > 0.05).

Crowding distance reduces 4.8×, reaching near-adult levels at eight years (P > 0.05).

More results

Removing age shows crowding distance, but not visual acuity, matters for reading (crowding distance-trigram: r = -0.24, P = 0.00065; crowding distance-repeated r = -0.25, P = 0.00049; visual acuity: r = -0.13, P = 0.075).

“
Conclusion · 1 of 2

Crowding develops more quickly and matures later than acuity and is significantly linked to children's reading performance, unlike acuity.

Conclusion · 2 of 2

Crowding distance measures may be more sensitive diagnostically than acuity for detecting exaggerated crowding found in strabismic amblyopia and may help identify children who struggle to read.

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