In:
Visual Neuroscience, Cambridge University Press (CUP), Vol. 21, No. 6 ( 2004-11), p. 827-834
Abstract:
Photopigment optical density (OD) of middle-(M) and long-(L)
wavelength-sensitive cones was determined to evaluate the hypothesis that reductions in the amount of photopigment are responsible for
age-dependent sensitivity losses of the human cone pathways. Flicker thresholds were measured at the peak and tail of the
photoreceptor's absorption spectrum as a function of the intensity of a bleaching background. Photopigment OD was measured at 0 (fovea),
2, 4, and 8 deg in the temporal retina by use of a 0.3-deg-diameter test spot. Seventy-two genetically characterized dichromats were
studied so that the L- and M-cones could be analyzed separately. Subjects included 28 protanopes with M- but no L-cones and 44
de uteranopes with L- but no M-cones (all male, age range 12–29
and 55–83 years). Previous methods have not provided estimates of photopigment OD for separate cone classes in the foveola. In this
study, it was found that foveolar cones are remarkably efficient, absorbing 78% of the available photons (OD = 0.65). Photopigment OD
decreased exponentially with retinal eccentricity independently of age and cone type. Paradoxically, the OD of perifoveal cones increased
significantly with age. Over the 70-year age range of our participants, the perifoveal M- and L-cones showed a 14% increase in capacity to
absorb photons despite a 30% decrease in visual sensitivity over the same period.
Type of Medium:
Online Resource
ISSN:
0952-5238
,
1469-8714
DOI:
10.1017/S0952523804216030
Language:
English
Publisher:
Cambridge University Press (CUP)
Publication Date:
2004
detail.hit.zdb_id:
1489922-X
SSG:
12
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