Related Experiment Video
Updated: May 22, 2026
09:47
A Method to Quantify Visual Information Processing in Children Using Eye Tracking
Published on: July 9, 2016
Crowding ratio in young normally sighted children
Marjoke J Dekker1, Florine Pilon, Mieke M C Bijveld
1Bartiméus Institute for the Visually Impaired, Ophthalmology, Zeist, Netherlands. mdekker@bartimeus.nl
Strabismus
|May 23, 2012
Summary
The crowding ratio (CR) in children aged 4-12 is typically below 2.0 for near vision and for distance vision after age six. A CR above 2.0 in older children may indicate visual impairment.
Area of Science:
- Ophthalmology
- Pediatric Optometry
- Vision Science
Background:
- The crowding ratio (CR) is a measure used in vision testing.
- Understanding normal CR values in children is crucial for identifying visual anomalies.
Purpose of the Study:
- To establish normative data for the crowding ratio (CR) in a pediatric population.
- To define reference values for CR in children aged 4-12 years.
Main Methods:
- The study involved 62 normally sighted primary school children aged 4-12 years.
- Crowding ratio was assessed for both distance and near vision using LEA symbol charts.
Main Results:
- The CR was significantly better (lower) for near vision compared to distance vision across all ages.
- For distance vision, the upper limit of normal CR was found to be less than 2.0 from the age of six.
- Near vision CR values were consistently below 2.0 for all participants.
Conclusions:
- The crowding ratio (CR) can be readily measured in school-aged children using standard vision tests.
- A CR exceeding 2.0 in children over six years old, especially for distance vision, is considered abnormal and warrants further investigation.
- Elevated CR values may be indicative of conditions such as cerebral visual impairment (CVI).
Related Concept Videos
01:29Sight Distance in a Vertical Curve
Sight distance on vertical curves is critical in roadway design. It ensures drivers can see far enough ahead to identify and respond to hazards effectively. This directly impacts safety, driver comfort, and the overall efficiency of the transportation network.Vertical curves are classified into crest and sag curves based on their geometry. For crest curves, sight distance is determined by the line of sight between a driver's eye and a small object on the road's surface. Design parameters for...
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...