Kindergarten Chart Likely Underestimates Visual Acuity in Pediatric Patients

The Kindergarten/Sailboat chart has poor agreement with the chart using Lea symbols, researchers found in a study published in Optometry & Visual Performance.

The need for validated distance visual acuity assessments that provide sensitive, uniform data for communicating about patients’ visual abilities extends to pediatric patients who are not yet able to read. The Kindergarten chart, also known as the Sailboat chart, is not standardized. Researchers attempted to determine the validity of the Kindergarten chart by comparing it with the Lea symbols chart in Massachusetts Visual Acuity Testing (MassVAT) format.

The study included a convenience sample of 51 pediatric patients (42% girls, mean age 5.7±1.7 years) from 2 school districts. The researchers tested visual acuity at 10 feet in 1 eye of each individual (24 right eyes) using both charts in randomized order. The researchers reduced distance between the patient and the chart to 5 feet when the individual became unable to read further on the chart. The patients read the Kindergarten chart verbally and pointed to match optotypes, or verbally read the Lea symbols chart. Patients received credit for the line if they identified at least 3 of 5 optotypes on the Lea symbol chart or at least 50% of the optotypes on the Kindergarten chart.

The approximate 1-line difference in both scoring methods was significantly different between the charts (P <.001 95% LOA ±0.28 for both).

Intraclass correlation coefficients showed moderate levels of agreement (0.72 and 0.71) in letter-by-letter and whole-line criterion and excellent levels of agreement between scoring criteria in both charts.

Failure rates were different between the charts and between scoring criteria. While 6 children failed the Lea symbols chart, 12 children failed the Kindergarten chart in line-by-line criteria, and 17 failed it in letter-by-letter criteria. Analyzing differences in failure rate by line-by-line criterion, the researchers found that 6 children failed the Kindergarten chart but passed the Lea symbols chart in the same method, and 11 children failed the Kindergarten chart but passed the Lea symbols chart.

The Kindergarten chart was not uniform in lines or spacing between lines, non-logMAR line progression steps (20/32 for Lea symbols, 20/30 for Kindergarten), and discrimination of optotypes.

The Kindergarten chart could refer pediatric patients unnecessarily, the researchers report. They recommend optometrists use a validated visual acuity chart or, if they use the Kindergarten chart, to give credit for 1 more line read to match the visual acuity from a Lea symbols chart. The optotypes on the Kindergarten chart may not be familiar to all children, according to the investigators. The researchers also suggest clinicians should not use colored versions of the chart because there may be low color contrast.

“The lack of documented methodology in the development of the Kindergarten chart in concert with this study’s findings do not support the use of this chart to assess visual acuity,” report the investigators.

Reference

Ng JS, Contreras M. Validity of the kindergarten chart to measure pediatric visual acuity. Optom Vis Perf. 2021;9(3):165-72.