Abstract
Purpose: :
To determine how the spectral transmittance of the aging lens affects macular pigment optical density (MPOD) measured by heterochromatic flicker photometry HFP) employing light emitting diodes (LED).
Results: :
Age has a significant effect on the measured value of P if V() is not adjusted for age. The effect is greater for older subjects with high MPOD. E.g., if subjects aged 20 and 80 provide a log (IF/IP) of 0.5 when tested by HFP, their peak MPODs from eqn. 1 are 0.753 and 0.889, respectively. If a fixed, standard V() is used, it is 0.768 for both subjects. For the simulated groups of subjects, peak MPODs were characterized by flat regression lines, i.e. no age-related change in their true MPOD. However, calculations revealed that if such subjects were tested by HFP, and eqn. (1) was used without an age correction for V(), the results would indicate an apparent age-related decline in MPOD of ~ (1.44±0.51)x10-2 OD units/decade.
Conclusions: :
HFP employing broad-band light sources, e.g. LEDs, gives erroneous MPOD if the aging lens is not taken into account. The discrepancy is more pronounced in older subjects leading to an apparent age-related decline in MPOD. Studies in which such declines have been reported may need to be re-examined.
Keywords: macular pigment • carotenoids/carotenoid binding proteins • cataract