Measurement of visual acuity with a digital eye chart: optotypes, presentation modalities and repeatability

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Digital eye charts are increasingly used for visual acuity (VA) testing.
• These charts allow for diverse optotypes, presentation methods, and crowding techniques.

Purpose of the Study:

• To investigate VA measurement differences using digital eye charts.
• To compare various optotypes and presentation procedures.
• To assess the repeatability of digital VA measurements.

Main Methods:

• Two groups of 52 young adults (18-31 years) were tested.
• VA thresholds were measured using LEA Symbols, Tumbling E, and Landolt Rings.
• Monocular/binocular conditions, single line, and QUEST presentations were employed, alongside paper eye-chart comparisons.

Main Results:

• LEA Symbols showed lower thresholds.
• Presentation modality significantly impacted thresholds.
• QUEST procedure yielded better thresholds for Landolt Rings and Tumbling E compared to line presentation.
• Single letter and line presentations performed similarly, outperforming block presentation.
• Paper eye-charts demonstrated superior VA values.
• Repeatability was good across all methods, with QUEST showing the best agreement.

Conclusions:

• The QUEST presentation modality offers improved thresholds over line presentation, except for LEA Symbols.
• Digital eye chart users must recognize that optotypes and presentation methods yield different VA thresholds.
• Tailored thresholds are necessary for each optotype and presentation modality for accurate VA assessment.