Viénot, Bailacq, Le Rohellec, ICVS, Braga Spectral power distribution and pupil aperture Françoise Viénot MNHN-CRCC, Paris, France Acknowledgements: Solenne Bailacq, Jean Le Rohellec, observers, and LedToLite TC169-Princeton 2010

Viénot, Bailacq, Le Rohellec, ICVS, Braga Motivation When the correlated colour temperature of the light increases, 1.Observers reported an increase of brightness while their pupil constricts. 2.Calculations show that all S-cones, melanopsin and rods excitations increase. Viénot, Durand, Mahler, J. Mod. Optics (2010) Would it be possible to isolate S-cones, or melanopsin, or rods response to investigate their contribution to pupil aperture? Viénot, Bailacq, Le Rohellec, Ophthalmic and Physiologicall Optics (in press)

Viénot, Bailacq, Le Rohellec, ICVS, Braga Outline The silent substitution method Pairs of illumination Recording the relative pupil diameter Results Conclusion

Viénot, Bailacq, Le Rohellec, ICVS, Braga The silent substitution method We used colour light emitting diodes (LEDs)

Viénot, Bailacq, Le Rohellec, ICVS, Braga The silent substitution method Five photoreceptorsFive colour LEDs Specification of the stimulus in any colour space Linear relationship between two 5-D spaces Lights that vary along one photoreceptor dimension only

Viénot, Bailacq, Le Rohellec, ICVS, Braga Planning pairs of illumination Distribution of the photoreceptor signals    “Rods ”S-cones” ”Melanopsin” ”Melanopsin ”Melanopsin high contrast” high contrast” with rods”    Contrast

Viénot, Bailacq, Le Rohellec, ICVS, Braga Planning pairs of illumination “Melanopsin with rods”

Viénot, Bailacq, Le Rohellec, ICVS, Braga Recording the relative pupil diameter Experimental set-up: –LEDs, light booth and digital camera Luminance about 35 cd/m²  N D U R F 

Viénot, Bailacq, Le Rohellec, ICVS, Braga Recording the relative pupil diameter Experimental set-up –LEDs, light booth and digital camera –Measuring the pupil diameter Five successive pictures, after one minute adaptation

Viénot, Bailacq, Le Rohellec, ICVS, Braga Overall results ** Isolated "Melanopsin “Melanopsin " Rods" "Melanopsin“ "S-cones" high contrast with Rods “Isolated rods “Isolated Isolated "Melanopsin “Melanopsin high contrast“ melanopsin“ "S-cones" high contrast with Rods

Viénot, Bailacq, Le Rohellec, ICVS, Braga Main results No differential pupillary response was observed with a variation of the rods, or the S-cones, or the melanopsin excitation alone. A differential pupillary response could be obtained at constant luminance (but different white colour) only with a variation of the melanopsin stimulus of high contrast. A differential pupillary response could be obtained with a variation of melanopsin excitation associated with a variation of the rod excitation.

Viénot, Bailacq, Le Rohellec, ICVS, Braga Conclusions The spectral profile of the SPD of the light might modify the pupil reflex. Would it have consequences on visual comfort? Should we take this effect into account when designing LED spectra? Thank you