Macular pigment regeneration upon smoking cessation
Abstracts
Initial Award Abstract |
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In the past year, two important studies have revealed that smoking is a risk factor for the most prevalent blinding disease, Age Related Macular Degeneration (ARMD). ARMD is not treatable. The link between smoking and ARMD has also been established. There is a pigment in the eye that protects the small high acuity area of the retina, the macula, from damaging effects of light in the blue range. The pigment is termed the macular pigment (MP) and is derived from organic chemicals called carotenoids that come from foods we eat. Apparently, smoking lowers the density of, and even can eliminate, the MP.
The purpose of this study is to investigate how and to what degree MP returns after people stop smoking. If this return can be demonstrated, then it forms the basis for a tool that might prove useful in smoking cessation efforts, since Americans fear blindness more than any other disease. Young Americans take up smoking, despite clear warnings that smoking may lead to cancer and to other diseases. However, smoking-related diseases may not occur until much later in life. When asked, teens claim that they might consider not smoking if an immediate effect on their health could be demonstrated to them. Unlike cancer for example, ARMD has a precursor (MP depletion) that can be measured non-invasively and that can be visualized by the patient.
An objective, non-invasive measurement of MP can be done in a laboratory using specialized optical apparatus. The subject looks at some carefully selected flashing lights and adjusts them until the flashing is minimum. This is done twice, taking only a few minutes. The setting tells, through a calculation, just how much MP is in the eye. A subjective measurement can also be made with a personal computer which doesn't require a special laboratory. In a word processor one creates a 1 column / 2 row table. One fills the top window with a bright yellow color and the bottom with a bright blue color. If one stares at the yellow for a while and then looks at the blue, one sees a dark spot wherever one looks. The spot (called Maxwell's Spot after its 19th century discoverer) fades after awhile, but while present its darkness can be subjectively graded on a 0 to 10 scale. The spot shows the presence of MP. The darker it is the more MP. Many smokers would have no visible spot at all.
In this study we plan to measure MP both objectively and subjectively in a group of 40 young adult smokers who give up smoking as part of a University-sponsored smoking cessation class. The class meets monthly. The measurements, also made monthly, can be used to gauge the rate of return of MP after smoking cessation. This biological endpoint is presently unknown, but would be useful to scientists studying the dynamics of biochemical changes due to smoking, and would be potentially valuable as a tool for use in a smoking cessation or prevention trial. |
Final Report |
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Aims: Recent research has revealed that smoking is a risk factor for the most prevalent blinding disease, Age Related Macular Degeneration (ARNID). ARMD isn't treatable. The link between smoking and ARMD may have been found. There is a pigment in the eye that protects the small high acuity area of center of the retina, called the macula, from damaging effects of light in the blue and especially ultraviolet range. The pigment is termed the macular pigment (MP) and is derived from organic chemicals, carotenoids, in the foods we eat. Apparently, smoking lowers the density of and even can eliminate the MP. Our objective was to study how rapidly, and to what degree, MP returns after smoking has been stopped. If this return could be demonstrated, then we thought it would form the basis for a tool that might prove useful in subsequent smoking cessation efforts. Here's why. Americans fear blindness more than any other disease. Young Americans take up smoking, despite clear warnings that smoking may lead to cancer and to other diseases. Such diseases, are like AR1VII), but not in all respects. They may not occur or they may, and if they do the occurrence is much later in life. Teens claim, when asked, that they might consider not smoking if an immediate effect on their health could be demonstrated to them. Unlike cancer for example, ARMD has a suspected precursor, MP depletion, that can be measured non-invasively and that can be visualized by the patient.
Accomplishments: We have developed a new, non-invasive measurement of MP. The subject looks at some carefully selected flashing lights (LEDs) of differing color. but which are seen in the same direction. The lights are controlled by a computer. The subject adjusts their brightness ratio until the flashing is minimum. That ratio, of the brightness of one to that of the other tells, through a calculation, just how much MP is in the eye. This apparatus is easily exportable to a doctor's office or to clinics or classrooms because the only sophisticated element involved is the software to run it.
Our measurements to date have been constrained by an unexpected lack of available smokers willing to quit. Nonetheless, we have been able to make some measurements and these clearly show the type of trend that we anticipated. (a) A smoker's macular pigment density (avg. = 0.2) averages less than that of age-matched non-smokers (avg. = 0.4), although there is considerable variance across subjects. As this result accords with earlier published findings it supports the view that our new device is making the correct measurement. (b) A smoker's macular pigment density tends to increase over time. Measurable increases have been observed in two smokers (0.13 increased to 0.25 after 15 weeks and 0.35 went up to 0.5 after 20 weeks).
Next Steps: We plan to examine fundus photographs of these subjects in order to see whether or not the macular pigment density can be abstracted in that way. |
