The conversion of bulbar redness grades using psychophysical scaling.

Area of Science:

• Ophthalmology
• Psychophysics
• Image analysis

Background:

• Bulbar redness grading scales are crucial for diagnosing ocular conditions.
• Standardization of redness assessment across different scales remains a challenge.
• Previous studies lacked a method to directly compare perceived redness between scales.

Purpose of the Study:

• To investigate the effect of reference anchors on perceived bulbar redness using psychophysical scaling.
• To establish a method for converting grades between different bulbar redness scales.
• To assess the reliability of existing redness grading scales.

Main Methods:

• Ten participants performed anchored scaling, arranging images from McMonnies/Chapman-Davies, IER, and Efron scales against reference images (0-100 range).
• Perceived redness was averaged across observers for each image.
• Anchored scaling data were compared to previous non-anchored scaling data.

Main Results:

• Perceived redness varied significantly within each scale (p < 0.001).
• Anchored scaling generally shifted perceived redness lower compared to non-anchored scaling.
• The rank order of images remained consistent between anchored and non-anchored scaling (Spearman's ρ = 0.99).

Conclusions:

• Redness assessment appears to rely on within-scale characteristics, termed clinical scale constancy.
• The findings support the use of perceived redness data for cross-calibrating different grading scales.
• Practitioners can use this data to reconcile grading estimates between scales.