[Contour interaction in the examination of visual acuity]

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Visual acuity charts are essential tools for assessing vision.
• The distance between optotypes (letters or symbols) on these charts can influence measurement accuracy.
• Standardization of interoptotype distance is lacking, potentially affecting clinical interpretation.

Purpose of the Study:

• To investigate the impact of interoptotype distance on visual acuity measurement.
• To determine if a smaller, constant interoptotype distance enhances sensitivity and specificity.
• To propose a method for reporting measurement validity based on interoptotype distance.

Main Methods:

• Analysis of visual acuity measurements using charts with a constant small interoptotype distance (5.5' minutes).
• Comparison of sensitivity and specificity of measurements with varying interoptotype distances.
• Development of a formula to calculate angular interoptotype distance.

Main Results:

• A small, constant interoptotype distance (5.5' minutes) significantly enhances the sensitivity of visual acuity testing for detecting functional deficits.
• This improved sensitivity is achieved without a reduction in the specificity of the measurement.
• The proposed specification of the distance between the last recognized optotypes allows for an estimation of the measurement's validity.

Conclusions:

• Optimizing interoptotype distance is critical for accurate visual acuity assessment.
• A constant, small interoptotype distance improves the detection of vision impairments.
• Reporting interoptotype distance enhances the reliability and interpretability of visual acuity measurements.