Ethnicity and Genetics of Glaucoma
Glaucoma is one of the major causes of irreversible blindness in the world. Since the disease is usually asymptomatic and progresses gradually without any symptoms until advanced stages, its diagnosis is often delayed. It is therefore essential to know the predisposing factors, and ensure regular annual comprehensive eye examination, if you are in anyway at risk of disease.
The risk factors for glaucoma include:
Age: Age more than 40 for angle closure glaucoma, and age more than 60 for open angle glaucoma.
Gender: women are at a higher risk than men.
Family history of disease: People with parents or siblings with glaucoma are at a higher risk of the disease.
Steroid use: Use of steroids, especially steroid drops increases the risk of glaucoma. Certain other drugs also predispose patients to glaucoma.
Diabetes: Diabetes is a major risk factor for glaucoma, with the incidence of glaucoma being twice as much as normal population. Other endocrine disorders like thyroid disease also show a weak correlation with developing glaucoma.
Trauma, including surgery on the eye: Trauma is also known to predispose the eye to glaucoma.
High eye pressure: Increased eye pressure increases the risk of glaucoma.
Anatomical predisposition: Decreased thickness of the cornea is also associated with rapid progression of glaucoma, and predisposes the eye to glaucoma. Decreased anterior chamber depth, decreased axial length, narrow anterior chamber angle and increased lens thickness can predispose the eye to PACG.
Ethnicity of glaucoma:
There are special racial subtypes who are more predisposed to certain types of glaucoma.
Prevalence of glaucoma in Africans and Latinos is significantly greater than in Caucasians. Africans are also more likely to develop glaucoma at a younger age and suffer blindness from the disease.
Almost 90% of all glaucoma cases in Caucasians are of primary open angle glaucoma (POAG).
Asians, including Indians, are at a greater risk for a different form of glaucoma called primary angle closure glaucoma (PACG). In fact, almost 50% of glaucomas in this region are PACG. PACG is more rapidly progressive and associated with a higher risk of blindness. It is also, however, easier to treat, if detected on time.
Read Also: (Cataract Surgery in Eyes with Glaucoma)
Genetics of glaucoma
The underlying genetics of glaucoma is still under investigation by research scientists and its genetic basis is as yet, not part of clinical practice. However, certain genetic mutations and subtypes have been associated with certain types of glaucoma. These include:
1. Primary Open Angle Glaucoma: Mutations in genes like myocilin, optineurin, and CYP1B1 have been associated with POAG. Exfoliative glaucoma, which is an aggressive form of open angle glaucoma, has been shown to be associated with mutations in genes LOX1 and CNTNAP2.
2. Primary Congenital Glaucoma: Sometimes, children may be born with glaucoma, or develop the disease at a very young age, even though glaucoma is primarily a disease of the elderly. Congenital glaucoma is more common in Middle East and Central Europe. Research shows that mutations in gene CYP1B1 may cause glaucoma in children.
3. Primary Close Angle Glaucoma– PACG may be associated with mutations in genes like PLEKHA7, PCMTD1/ST18, and COL11A1.
It must be kept in mind that all genetic studies reveal only a correlation, and may or may not be the real cause of disease. In fact, the risk factors discussed above in the first section of this article still remain the most common causes of glaucoma.