Although we Americans are taught by our Constitution that everyone has equal rights and should be treated equally, Mother Nature does not abide by this law.
These lectures inspired me to do some of my own research on the subject. Does glaucoma discriminate by race? And if it does, how does it discriminate?
We have known for years that glaucoma discriminates by age (although it is possible for babies to have glaucoma older people are more likely to develop glaucoma than younger people). The study of how glaucoma discriminates against different races is a more recent topic for research.
The doctors at the UCLA Stein Eye Institute have done a yet to be published 5 year study comparing 135 African American eyes to 135 Caucasian eyes to find not only the prevalence of glaucoma in each group, but how each group responds to various drug and surgical therapies.
There have been many studies showing racial differences in glaucoma, and the kind of glaucoma in different racial groups.
There are two main types of glaucoma, primary open angle glaucoma (POAG), and Primary angle-closure glaucoma (PACG). Primary open angle glaucoma (POAG) is more prevalent among people of European and African descent. A sub-group of primary open angle glaucoma is Normal Tension Glaucoma (NTG). NTG is form of glaucoma where optic nerve damage occurs even though pressures in the eye are not elevated (high eye pressure is the most significant risk factor for open angle glaucoma). A Japanese study found NTG accounted for 92 percent of open angle glaucoma cases in Japan.
In studies such as the Baltimore Eye Survey and the Barbados Eye Study, researchers have investigated how glaucoma affects different black populations.
Glaucoma occurs about five times more often in African Americans. Blindness from glaucoma is about six times more common. In addition to this higher frequency, glaucoma often occurs earlier in life in African Americans — on average, about 10 years earlier than in other ethnic populations. It urns out that medications that work in lowering the pressure in the white population are less effective in the black population.
A study conducted by a group from the Wilmer Eye Institute, Johns Hopkins University in residents over the age of 40 years residing in two counties of Southern Arizona indicated that open-angle glaucoma is the leading cause of blindness among Hispanics. This study, named Proyecto Ver, also reported that only 38% of Hispanics with glaucoma were aware of their disease.
The Los Angeles Latino Eye Study (LALES), another large prevalence study funded by the National Eye Institute reported an overall prevalence of open-angle glaucoma among Hispanics to be nearly five percent — similar to that found amongst African Americans.
The LALES, like Proyecto Ver reported that Hispanics over age 60 are at particularly high risk of glaucoma. Approximately 75% of Hispanics with glaucoma in LALES were not aware that they had the disease.
EyeCare America, a public service program of the Foundation of the American Academy of Ophthalmology, has highlighted the fact that most Hispanic Americans are unaware they are at higher risk for glaucoma than Caucasian Americans. The recently conducted National Americans Eye Health and Eye Disease Survey found that 76 percent of Hispanics did not know that their ethnicity was a risk factor for glaucoma.
Although Primary Angle Closure Glaucom (PACG) is less frequent among Caucasians and blacks it is the most common glaucoma among Chinese. For Chinese living in urban areas, the ratio of those with PACG to POAG is 2 to 1 — twice as many Chinese living in bigger cities have angle-closure glaucoma than the open angle type. PACG is a more aggressive form of glaucoma and accounts for 90 percent of all cases of blindness from glaucoma in China.
There is great racial diversity among Asian populations, and these differences are represented in the presentation of disease among Asian patients. Studies have found that South Asians, ethnic Chinese, and Intuit Eskimos are at significantly higher risk for angle-closure glaucoma, whereas a study of a population of Japanese patients found ACG incidence to be much lower than in their Asian counterparts, but as stated above, the Japanese have the higher percentage on Normal Tension Glaucoma (NTG).
A study published in the February 2009 Archives of Ophthalmology looked at a large Japanese American patient group in San Francisco and found that the proportion of patients with normal tension glaucoma was 4 times greater than those with high tension glaucoma.
Although it is not known why certain racial groups have a higher percentage of people with Primary Open Angle Glaucoma (POAG) there is a reason that primary angle-closure glaucoma is so much more prevalent in East Asian populations.
In Asian eyes, the iris (the colored part of the eye) attaches to the sclera (the eye’s white, protective covering) in such a way as to form an anatomically narrower angle with less trabecular meshwork exposed.
Angle-closure glaucoma occurs when the iris blocks the trabecular meshwork, the eye’s drainage system, which leads to increased intraocular pressure (IOP). The increased IOP eventually causes damage to the optic nerve, which transmits visual signals from the retina to the brain. If the angle closes suddenly, there can be a sharp increase in eye pressure. Symptoms of acute angle-closure may include headaches, eye pain, nausea, rainbows around lights at night, and very blurred vision.
This does not explain why Japanese have less Primary Angle-Closure Glaucoma than Chinese.
What we can derive from all this is that Glaucoma definitely discriminates among the races and everyone should have their eyes checked regularly by an optometrist or ophthalmologist because primary open angle glaucoma may not have any symptoms.