People of African descent are significantly more likely to be beset with several medical conditions compared with ethnic Europeans. Rates of diabetes, HIV, cardiovascular disease and a number of other ailments are significantly higher — and the same is true for glaucoma.
Glaucoma is particularly prevalent among African Americans and in other populations of people of African descent worldwide. This holds true in South America, Europe, and Africa itself. No matter where they live are they significantly more likely to be affected by glaucoma than their neighbors, no matter their racial background.
Glaucoma is, of course, an exceptionally common condition that ophthalmologists treat on a day-to-day basis. Unlike another leading cause of blindness, cataracts —which can usually be treated with surgery — glaucoma is far more insidious and difficult to treat. It usually begins slowly and causes no symptoms until the damage is done.
There are several forms of glaucoma, the most common of which is primary open angle glaucoma (POAG), which tends to develop slowly over many years. Acute angle closure glaucoma is less common and caused by a blockage in the eye’s drainage, which can raise the pressure inside the eye very quickly. Secondary glaucoma is caused by an underlying eye condition like uveitis, and childhood glaucoma does exist, though it is extremely rare.
Vision loss caused by glaucoma cannot be recovered, therefore it is absolutely crucial to catch the disease as early as possible. This is particularly true for POAG, which often causes no symptoms at all.
Even Ophthalmology Has Its Inequalities
According to the Royal National Institute for the Blind, people of black African and Carribean descent in the U.K. are eight times more likely to develop glaucoma than their white European counterparts. In the United States, the Bright Focus Foundation reports that African-Americans are three to four times more likely to have glaucoma than white Europeans. It is a truly global health issue for Black populations.
So, why is this the case? This topic has generated considerable debate, producing several theories on why Black populations are more susceptible to glaucoma than others. They are more likely to have diabetes and high blood pressure, both of which are glaucoma risk factors, but so too is intraocular pressure (IOP), which is more evenly distributed across racial groups.
Some experts have postulated that the prevalence of glaucoma could be due to genetic differences, such as those that lead to differences in the anatomic structure of the optic nerve. Also, as African-descended populations worldwide are more likely to be over-represented in poorer socio-economic groups, particularly in the United States, access to care can be an issue. While this wouldn’t impact overall rates of glaucoma itself, lack of access would increase the chance of a patient going blind from glaucoma, as they may present with symptoms too late.
The African Descent and Glaucoma Evaluation Study (ADAGES) is one of the most definitive investigations on the issue. A large number of researchers from around the world studied 1,221 people of both African and European descent. These participants were grouped into three categories: those with no glaucoma, those with suspected glaucoma, and those with diagnosed glaucoma.1
The results were fascinating: Individuals of African descent had (1) thinner corneas (P<.001) across all diagnostic groups; (2) a higher percentage of reported diabetes mellitus (P<.001), high blood pressure (P < .001) and a lower percentage of reported heart disease (P=.001); and (3) worse pattern standard deviation for standard automated perimetry fields overall (P=.001) and within normal limits (P=.01); than individuals of European descent. No differences were present for mean IOP.
The ADAGES study tells us two things. First, that the risk factors of diabetes and high blood pressure, which are common in Black populations, have a causation factor with glaucoma. Secondly, and more importantly, there is a difference in corneal thickness between African and European descended populations.
Does the Solution Lie in the Cornea?
A number of studies have examined the issue of corneal thickness and susceptibility to glaucoma. The 2012 study, Is Corneal Thickness an Independent Risk Factor for Glaucoma?, while noting that corneal thickness can be recognized as an independent risk factor, ultimately concluded that diagnostically, it holds little value to clinicians. Instead, IOP was determined to be more valuable as a diagnostic parameter.2
We can reasonably conclude therefore that there is circumstantial evidence of the relationship between glaucoma and corneal thickness, but that further research is required. There are plenty of public health campaigns warning about the dangers of diabetes and high blood pressure. The market space is occupied, whereas corneal thickness research is more limited, which represents opportunity.
And the market for finding better treatment for glaucoma in African descended populations is huge. In sub-Saharan Africa alone, the prevalence of glaucoma can be conservatively estimated to be 10,000 people for every 1 million population.3 It is also the second leading cause of blindness after cataracts, causing 30% of cases. Other studies have also consistently shown that not only are African populations more susceptible to glaucoma, they also develop the condition and decline in health due to it more rapidly than their European counterparts.4
Glaucoma urgently needs further investigation and study to prevent thousands of cases of needless blindness every year. It would be a prescient moment to invest more resources into this condition and its effects in African descended populations, given the ongoing protests about race relations around the world. Progressively minded companies, in particular, would do well to take note of an opportunity for research and improved patient outreach.
References
- Sample PA, Girkin CA, Zangwill LM et al. The African Descent and Glaucoma Evaluation Study (ADAGES): Design and Baseline Data. Arch Ophthalmol. 2009;127(9):1136-1145.
- Medeiros FA, Weinreb RN. Is Corneal Thickness an Independent Risk Factor for Glaucoma? Ophthalmology. 2012; 119(3): 10.1016/j.ophtha.2012.01.018
- Cook C. Glaucoma in Africa: The Size of the Problem and Possible Solutions. J Glaucoma. 2009;18(2):124-128.
- Kyari F, Abdull MM, Bastawrous A et al. Epidemiology of Glaucoma in Sub-Saharan Africa: Prevalence, Incidence and Risk Factors. Middle East Afr J Ophthalmol. 2013;20(2):111-125.
