The rods are absent from the center of the retina and increase in number with retinal eccentricity to form a high-density (>150,000 rods/mm2) elliptical ring from 2 to 5 mm of retinal eccentricity, with the peak at 4 to 5 mm wider than the fovea. The interpersonal variability in the rod density for all age groups is very high (variation coefficient >45%) at the border of the rod deprived zone, high within 1 mm of the fovea and around the optic disk, and low (<15%) elsewhere. With aging, the rod density reduces in both the foveal and extrafoveal retina. The loss is higher in the high rod density ring. The number of rods within the central 8 mm in all retinas changes from 7.40 x 106 at age 45 to 3.60 x 106 at 82 years of age.
The gradient of the linear regression suggests an average loss of 648 rods/mm2/year in the central 28.5° of vision such that at age 90 the total number of rods is reduced to 69% of that at 34 years of age.
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