Short-wavelength-sensitive cones do not contribute to mesopic luminosity.

Area of Science:

• Vision science
• Photoreceptor physiology

Background:

• The Purkinje shift describes the change in luminosity perception from scotopic (rod-dominant) to photopic (cone-dominant) vision.
• The potential role of short-wavelength-sensitive cones (S cones) in this transition has been debated.

Purpose of the Study:

• To investigate the direct contribution of S cones to luminosity perception during the Purkinje shift.
• To determine if S cones influence mesopic and photopic vision.

Main Methods:

• Utilized flicker photometry with two reference lights (441 and 481 nm) differing in S-cone stimulation.
• Measured luminosity functions across a 5-log10 unit range of light levels (scotopic, mesopic, photopic).
• Employed a novel technique leveraging differential Stiles-Crawford effects of rods and cones.

Main Results:

• Luminosity functions derived from the two reference lights were indistinguishable at all tested light levels.
• A significant difference in S-cone stimulation (over 1 log10 unit) did not alter the measured luminosity.

Conclusions:

• S cones do not contribute to photopic luminosity.
• S cones do not contribute to mesopic luminosity.
• The findings challenge the hypothesis that S cones play a significant role in the Purkinje shift.