Bleaching constants for human rods and cones

Receptor	I0 *	Region	Reference
Rods	4.4 log scot. td	Periphery	Rushton (1972)
L- & M-cone mixture	4.3 log phot. td	Fovea	Rushton & Henry (1968)
L-cone	3.89 log phot. td	Fovea	Rushton (1965)
M-cone	3.89 log phot. td	Fovea	Rushton (1963)

 

*the intensity at which the fractions of unbleached and bleached pigment are both 0.5.

 

Notes

Formulae

(1) Equilibrium bleaching

 

,

 

where p is the percentage of unbleached pigment, I is the intensity if the bleaching light in trolands and I₀ is the half-bleaching constant in trolands.

 

(2) Short bleaching exposures

 

,

 

where p is the percentage of unbleached pigment, I is the intensity if the bleaching light in trolands and t  is the time in seconds.

 

References

Baker, H.D. & Rushton, W.A.H. (1965). The red-sensitive pigment in normal cones. Journal of Physiology, London, 176, 56-72.

Campbell, F.W. & Rushton, W.A.H. (1955). Measurement of the scotopic pigment in the living human eye. Journal of Physiology, London, 130, 131-147.

Ripps, H. & Weale, R.A. (1969). Flash bleaching of rhodopsin in the human retina. Journal of Physiology, London, 200, 151-159.

Rushton, W.A.H. (1972). Visual pigments in man. In Dartnall, H.J.A. (ed.), Handbook of sensory physiology VII/I. New York: Springer-Verlag.

Rushton, W.A.H. (1963). Cone pigment kinetics in the protanope. Journal of Physiology, London, 168, 374-388.

Rushton, W.A.H. (1965). Cone pigment kinetics in the deuteranope. Journal of Physiology, London, 176, 38-45.

Rushton, W.A.H. & Henry, G.H. (1968). Bleaching and regeneration of cone pigments in man. Vision Research 8, 617-631.