It has been shown that the macular pigment absorbs blue light.
This is why the program evaluates the density of the macular pigment by comparing the thresholds of perception of blue light and red light with a staircase technique similar to the technique used in automated perimetry.
This technique presents several advantages:
• the staircase thresholding technique is much easier for patients than the heterochromatic flicker technique.
• it does not require the dilation of pupils
• it is quite fast (less than 3 minutes per eye).
These systems include a built-in fixation monitoring. A standard PC operating under Windows is used for the control of the instrument as well as for the storage and printout of results.
The curves hereby show results from normal subjects for the detection thresholds of blue and red light
measured at the fovea and in pericentral locations.
In normal subjects, the blue thresholds present a relative attenuation of about 0.6 log units in the fovea location, indicating the presence of macular pigment that absorbs blue light.
The first step of the analysis is to compensate for the alteration of blue thresholds due to intraocular media transparency.
This is achieved by substracting the measurement at the pericentral location (affected only by intraocular media)
from the measurement at the fovea (involving both pigment and intraocular media).
In a second step, the result is compared to an age corrected normal data base that has been developped from a population of subjects with normal eyes and a nutritionaly recommended diet (more details in the publication cited in references).