Rods affect S-cone discrimination on the Farnsworth-Munsell 100-hue test

Area of Science:

• Vision Science
• Photoreceptor Physiology
• Color Perception

Background:

• Rod photoreceptors contribute to vision in dim light.
• Their precise role in color discrimination, especially under mesopic conditions, remains debated.
• Understanding rod-cone interactions is crucial for explaining visual performance variability.

Purpose of the Study:

• To quantify the influence of rod photoreceptors on hue discrimination.
• To investigate how rod activity affects color perception across various light intensities.
• To determine if rods introduce specific color confusions.

Main Methods:

• Utilized the Farnsworth-Munsell 100-hue test to assess color discrimination errors.
• Measured rod influence by comparing error scores after dark adaptation versus during the cone plateau.
• Evaluated performance at mesopic (23, 9, 3 td) and photopic (158 td) light levels.

Main Results:

• Rods caused a significant loss in hue discrimination, particularly along the tritan axis (blue-yellow confusion).
• This effect was observed at mesopic light levels, indicating impaired S-cone pathway function.
• No specific rod-induced confusion axis was identified, suggesting a general disruption rather than specific color shifts.

Conclusions:

• Rod photoreceptors negatively impact hue discrimination, primarily affecting blue-yellow color perception.
• The impairment is most pronounced under mesopic conditions, mediated by S-cone pathways.
• Rods disrupt color vision by elevating tritan errors, especially at moderate light levels.