Towards a colorimetric characterization of the human iris

Area of Science:

• Ophthalmology
• Color Science
• Biomedical Optics

Background:

• Accurate iris color quantification is essential for various applications, including prosthetics and understanding ocular conditions.
• Existing methods may not fully capture the complexity of iris appearance.
• The human iris exhibits significant variability in color, texture, and pattern.

Purpose of the Study:

• To develop and evaluate a novel spectroradiometric approach for the quantitative determination of iris color.
• To assess the consistency and correlation of color measurements across artificial, prosthetic, and real irises.
• To investigate the role of color versus other visual factors (patterns, textures) in iris appearance perception.

Main Methods:

• Spectroradiometric measurements of 72 artificial irises under controlled illumination and geometry.
• Color analysis in the CIELAB color space.
• Complementary color measurements of 25 ocular prostheses and 40 real human irises.
• A visual experiment involving 11 observers matching ocular prostheses using artificial irises.

Main Results:

• Artificial iris samples showed no distinct groupings in the CIELAB color space.
• Measurements of different iris regions and overall irises were well-correlated.
• Color measurements across all sample types (artificial, prosthetic, real) demonstrated high consistency (average standard deviation < 1.0 for a*, b*, L* coordinates).
• A simple color-difference criterion matched observer judgments in only 18% of cases during the visual experiment.

Conclusions:

• Spectroradiometry provides a consistent method for quantitative iris color measurement.
• While iris color is a significant factor, it is insufficient on its own for accurate iris characterization.
• Iris patterns and textures play a critical role in the visual perception and matching of iris appearance, necessitating their inclusion in future models.