For patients at risk for AMD, it is critical that they know how much protective pigment they have in their macula. A macular densitometer instrument can measure the macular pigment, a yellowish substance in the back of the eye that helps protect the eye from the destructive effects of light, and give a clearer understanding of the patient’s risk for developing macular degeneration.
Lower levels of macular pigment have been demonstrated in patients with macular degeneration, and is under investigation as a risk factor for development of the disease. Studies on primary relatives of macular degeneration patients suggest that these individuals have an increased risk of having lower levels of macular pigment as well.
Professor Billy Wooten designed, built and tested the macular densitometer. The present instrument evolved over a period of many years of basic research.
How does it work?
The instrument uses selected light-emitting diodes (LEDs) to measure macular pigment. A patient looks directly into the machine and adjusts a flickering light until it stops flickering, then repeats the process with a flickering light in peripheral vision. By comparing the two measurements, it can determined how much light is absorbed by the macular pigment and therefore how much macular pigment a patient has.
The underlying principal is called heterochromatic flicker photometry. The included software calculates optical density, stores the data, fits an exponential function to the data (if you do 4 points), and plots that curve through the data.
Why is measuring macular pigment important?
Generally, patients with low macular pigment need to be on a carotenoid-building supplement to help mitigate risk for AMD. (Those already diagnosed with AMD can benefit from the slowing or stopping of the progression of AMD if they increase their macular pigment.) To determine at what point your patients need supplementation, a simple and reliable test using a densitometer can give immediate results (and reproducible) to not only indicate whether the patient has low macular pigment, but when to start supplementing with lutein, zeaxanthin and meso-zeaxanthin. As you follow up with your patients at regular 6-12 month intervals, you will be able to demonstrate to them that the treatment plan is working (provided the patient has been compliant). Patients appreciate the added reassurance they get from taking a proactive part in their eyecare.
