Replies to post #135298 on Biotech Values

[mouton29]

Exfoliation syndrome -- here is a very lengthy 1994 article by my glaucoma specialist, Dr. Ritch. There is some interesting epidemological discussion starting around page 847.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1298528/pdf/taos00007-0858.pdf

Here is part of the discussion. Exposure to sunlight has been offered as an explanation by some. I've been told by another ophthalmologist that diagnosis is not so simple and is frequently missed (it was initially missed in my mother), so that could explain some of the variation:

What stands out is that, from one examiner to another, the prevalence rates in a single country often vary threefold or more. In Scandinavia, the highest prevalence rates (in studies of persons over age 60) have been reported from Iceland (about 25%),28,33 and Finland (over 20%)26,33,52 Rates in Norway and Sweden average about one-third of those in Iceland and Finland, and those in Denmark are significantly less. In the past few years, an increasing number of reports has come from countries in which exfoliation syndrome had been previously thought rare, reversing those opinions.

The most significant comparisons are those made among different populations by the same observer. Aasved32 examined persons over age 60 in nursing homes in Norway, England, and Germany and found prevalences of 6.3%, 4.0%, and 4.7% respectively. Forsius33 looked at a wide variety of ethnic groups, including Lapps, Eskimos, Icelanders, Peruvian Indians, and Tunisians. The prevalence of exfoliation syndrome in persons over age 60 ranged from 0% in Greenland Eskimos to 21% in Icelanders. He proposed that genetic isolation may be responsible for the high incidences of disease in countries such as Iceland and Finland. In a study in Siberia, Latukh62 found a low prevalence in the native Tchutchee, but a much higher rate among immigrants to the area.

The prevalence in the United States has generally been reported to be similar to that in Western Europe. In the Framingham Eye Study, prevalence rates for persons not specifically identified as having glaucoma rose from 0.6% for ages 52 to 64 to 5.0% for ages 75 to 85.36,37 Cashwell and Shields49,53 have found lower figures in Caucasian populations in the southern United States. In a screening of 2121 people, exfoliation syndrome was present in only 1.6% of non-glaucomatous persons over age 60.49,53 American blacks have a much lower prevalence of than do whites.48,49,53,56

The prevalence of exfoliation syndrome may also vary within countries in similar environments and over short distances. In France, the overall prevalence in persons over age 70 is about 5.5%, ranging from 20.6% in Brest, to 3.6% in Toulon.43,47 Ringvold et al44,47 found prevalence rates of10.2%, 19.6%, and 21.0% in three closely situated municipalities in central Norway.

The reasons underlying true variation in prevalence rates both from one population to another and within more-or-less homogeneous populations remain to be explained. Some authors have suggested a correlation between the prevalence of exfoliation syndrome and exposure to sunlight. For example, among Australian aborigines, Taylor63 found exfoliation syndrome to be more common among those living farther north, which correlated positively with the annual total global radiation level. Exfoliation syndrome was associated positively with the occurrence of cataract and with climatic droplet keratopathy. Taylor suggested that senile cataracts are related to the amount of ultraviolet radiation and exfoliation syndrome is related to global radiation. However, Heriot et al39 screened 986 Polynesian Maori in Raratonga, which has the same latitude and climate, and found exfoliation syndrome in only 3 persons. The authors speculated about the scattering effect of the atmosphere perhaps being dependent on water vapor content and ultraviolet light. Mohammed and Kazmi64 found a much greater prevalence of exfoliation syndrome in tribes living in mountainous regions of Pakistan than among those living in lowland valleys. Forsius,33 however, found relatively little in Peruvian Indians living at an altitude of 4000 meters.