While African ancestry is a known glaucoma risk, researchers say no such positive correlation exists between glaucoma and darker skin pigmentation, according to a study published in the Journal of Glaucoma.
The research included patients in Addis Ababa, Ethiopia with glaucoma who were being scheduled for trabeculectomy, as well as a control group of patients without glaucoma. The median of triplicate skin melanin was the main measurement variable, and melanin levels of both the central forehead and the inner upper arm were tested.
Participants were 40 years or older and were aged-matched by group. The study spanned 2 years, between September 2016 and July 2018.
Research more than 2 decades old had suggested a connection between darker skin pigmentation and higher intraocular pressure, leading to an increased risk of glaucoma. However, those studies used a subjective measurement of skin color. This study shows a relationship between African ancestry and glaucoma, hypothesizing that the group of glaucoma patients tested would have increased levels of skin pigmentation.
Researchers used a Dermacatch colorimeter to measure the level of skin pigmentation, as it reliably differentiates skin melanin levels from levels of skin erythema. Measurements were taken in triplicate. The result did not show statistical significance between melanin of the inner arm and glaucoma. Mean values of melanin were 704 units in 76 glaucoma cases and 694 units in 152 controls (P =.69). Among the central forehead measurements, melanin measurements were 778 for cases and 753 for controls, also failing to show a significant connection (P =.63).
Despite these results, researchers remain reluctant to definitively determine the absence of a correlation between higher melanin levels and glaucoma due to the wide CIs of the primary analyses.
“Patients with glaucoma enrolled in this study typically had advanced disease, since their glaucoma had to be severe enough to be scheduled for trabeculectomy,” the study explains. Moreover, Ethiopians are genetically distinct from other African populations, and previous population-based studies suggest a higher prevalence of glaucoma in west African populations than east African populations.”
Giorgis A, Alsoudi A, Alemu A, et al. . The Relationship between melanin and glaucoma: a case-control study. J Glaucoma. 2020;29:1143-6. doi:10.1097/IJG.0000000000001652.