Rp. Tornow et R. Stilling, Variation in sensitivity, absorption and density of the central rod distribution with eccentricity, ACT ANATOM, 162(2-3), 1998, pp. 163-168
Purpose: To assess the human rod photopigment distribution and sensitivity
with high spatial resolution within the central +/-15 degrees and to compar
e the results of pigment absorption, sensitivity and rod density distributi
on (number of rods per square degree). Method: Rod photopigment density dis
tribution was measured with imaging densitometry using a modified Rodenstoc
k scanning laser ophthalmoscope. Dark-adapted sensitivity profiles were mea
sured with green stimuli (17' arc diameter, 1 degrees spacing) using a Tubi
ngen manual perimeter. Sensitivity profiles were plotted on a linear scale
and rod photopigment optical density distribution profiles were converted t
o absorption profiles of the rod photopigment layer. Results: Both the abso
rption profile of the rod photopigment and the linear sensitivity profile f
or green stimuli show a minimum at the foveal center and increase steeply w
ith eccentricity. The variation with eccentricity corresponds to the rod de
nsity distribution. Conclusion: Rod photopigment absorption profiles, retin
al sensitivity profiles, and the rod density distribution are linearly rela
ted within the central +/-15 degrees. This is in agreement with theoretical
considerations. Both methods, imaging retinal densitometry using a scannin
g laser ophthalmoscope and dark-adapted perimetry with small green stimuli?
are useful for assessing the central rod distribution and sensitivity. How
ever, at present, both methods have limitations. Suggestions for improving
the reliability of both methods are given.