Up to now age-related blindness or “age-related macular degeneration” (AMD) as it is medically called, has been a mystery. The retina is the light-sensitive area of the eye similar to the film in a camera. The “macula” is that part of the retina that has the highest visual acuity. Several studies have been conducted lately regarding age-related blindness that shed more light on this important health hazard of old age, studies that one day might even lead to a cure or powerful preventative measures to avoid it from ever developing.
One such study is the one by Dr. Johanna M. Seddon and co-workers published in the Feb. 11, 2004 issue of the Journal of the American Medical Association. Almost 1000 patients with various degrees of age-related degrees of blindness from the Age-Related Eye Disease Study (AREDS) were classified by the degree of their macular degeneration. I have produced the bar graphs below based on these studies.
Four groups were defined, namely those with no AMD who served as controls, those with mild AMD, those with moderate AMD and those with severe AMD who were legally blind. They suspected that an inflammatory marker in the blood stream of these patients, called C-reactive protein (CRP), might be present in the more severe cases of blindness when compared to the control group who did not have any inflammatory changes in the macula. As can be seen by the bar graph above this is exactly what the test results indicated. They also found that smokers (blue bars) tended to have slightly worse blood tests in terms of CRP (more inflammatory substances circulating in the system) within the same severity category of the age-related eye changes.
|CRP (mg/L) Levels in Various Degrees of Severity of Age-related Macular Degeneration (AMD)|
When the investigators studied the risk for the highest percentile of the CRP tests within various subgroups to show AMD they found several differences as is shown in the next table. First there was a low probability to develop AMD in a person with a normal looking macula and that risk was set at 1.0 as comparison. In contrast a person with a normal looking macula who smokes has a 1.5-fold risk of developing AMD later. Patients with a moderate degree of AMD have about a 2-fold risk of getting a severe degree of AMD later (smoking or not). It seems that once the inflammatory cycle has started, the process of causing a moderate degree of AMD is so strong that the effect of smoking will not add that much in comparison.
This is the first study of this kind that has established that CRP can be used as a screening for the risk to develop AMD. CRP has already been established as a test for monitoring progress in rheumatoid arthritis or to monitor for the risk of developing a heart attack or stroke.
Another study by Dr. Johanna M. Seddon and co-workers was published recently in the Archives of Ophthalmology. 261 people aged 60 years and older with established AMD were followed for 4.6 years and checked for deterioration. 101 patients had deterioration of their AMD.
|Risk of Developing Age-Related Macular Degeneration (AMD) in Highest CRP Percentile|
The authors analyzed the patients’ diet habits and found that increased fat intake was a high risk factor for deteriorating AMD. Both vegetable and animal fat had a 2-to 3-fold increased risk for deterioration of the AMD to a more severe stage (legal blindness). Fish, omega-3 fatty acid and nuts had a protective effect, but only when omega-6 fatty acid (linoleic acid) intake was low in the same group. The studies showed that the risk of age-related blindness was reduced by 40% when patients ate nuts at least once per week. The authors concluded that a “fat conscious diet” would be good for “maintaining good eye health” and at the same time be beneficial for prevention of heart attacks and strokes.
The authors will do further studies to investigate potential ways of helping patients with AMD and to understand the mechanisms of the disease process better.
References: 1. JAMA 2004;291:704-710 2. Arch Ophthalmol – 01-DEC-2003; 121(12): 1728-37
Last edited December 8, 2012