By Olusola Olawoye
The optic nerve in the human eye, barely an inch long, is a bundle of more than 1 million nerve fibres. This optic nerve connects the retina which is the light-sensitive tissue at the back of the eye, to the brain. Therefore, good vision requires a healthy optic nerve (nerve of vision).
Glaucoma is a group of diseases that damage this optic nerve can usually be halted with treatment but cannot be reversed once the damage is done.
This disease is a leading cause of health and social burden in Sub-Saharan Africa (SSA).1 Africa is disproportionately affected by glaucoma blindness accounting for 15% of blindness compared to 8% in the world.1 Reported prevalence of glaucoma in population based studies2,4,5 within SSA ranges from approximately 5 to 7% populations above the age of 40 to as high as 20% in those over age 80.2
In 2013, nearly 64.3 million people had glaucoma with Africa having the second highest number of cases after Asia.3 In 2020 it is estimated that this figure will rise to 76 million people and stand at111.8 million in 2040.
The disease often does not have any symptoms and vision lost cannot be regained, thus a huge challenge to diagnose it in good time before irreversible damage occur.
Africa will be disproportionately affected due to the expected increase in life expectancy and an aging population in the continent.3 In Africans, it is rapidly progressive, very aggressive, and often associated with high eye pressure also known as high intraocular pressures (IOP). Most of the risk factors for glaucoma development are also risk factors for its progression. Africans generally tend to have higher IOP.
Advancing age is yet another risk factor but Africans generally present at a younger age compared to other populations.
A positive family history of glaucoma is another important risk factor. Having an immediate family member with glaucoma has been consistently associated with an increased risk of POAG. It is estimated that siblings of affected individuals have nearly an 8-fold risk of POAG compared to siblings of unaffected individuals.
The association between POAG and family history is stronger when the affected relative is a sibling than a parent or child.7 Therefore, people with a family history of glaucoma are at increased risk of developing the disease and they are considered to be a ‘population at risk’. They are often advised to have regular eye screening/check-up.
Other causes are hypertension, diabetes, migraine, cerebrospinal fluid pressure, thyroid disorders, infectious and autoimmune diseases have also been associated with Primary open angle glaucoma. Genetics play a significant role in the pathogenesis of glaucoma. The prevalence of glaucoma is affected by race, family history, myopia and other genetic factors. People with sleep apnea, a sleep disorder in which breathing repeatedly stops and starts, are also at risk.
There are two major categories of glaucoma, this is open-angle glaucoma (OAG) and angle closure glaucoma. The “angle” in both cases refers to the drainage angle inside the eye that controls the outflow of the watery fluid (aqueous) that is continually being produced inside the eye. If the aqueous can access the drainage angle, the glaucoma is known as open angle glaucoma. If the drainage angle is blocked and the aqueous cannot reach it, the glaucoma is known as angle closure glaucoma. The high prevalence, early onset, and aggressive course of the disease present a high rate of glaucoma blindness in Africa.
Glaucoma care in Sub-Saharan Africa is hindered by the gross lack of adequate facilities and equipment for diagnosis, management and follow-up, paucity of human resources, socioeconomic, educational, and cultural/spiritual considerations.
In clinic populations, more than 40 percent of patients diagnosed with Primary open angle glaucoma (POAG) are blind in one or both eyes.
Earlier diagnoses of glaucoma and appropriate management is crucial to avoid needless blindness from the disease in Africa. Clinic studies done in Africa have reported that a significant proportion of patients present to the eye clinic at a late stage of the disease. Since glaucoma is asymptomatic, many patients do not see a need for screening. This is worse in SSA where there is a high rate of illiteracy, poverty and ignorance. Creating awareness and providing appropriate knowledge of the disease can influence regular eye checks and earlier detection of the disease.
The Glaucoma Society of Nigeria organized radio jingles, talk shows glaucoma walk and walk for vision in order to raise awareness about the disease. I participated in the free eye screening and in the radio talk show. Several other programs are also being carried out all over the world to create awareness.
This year the World Glaucoma Week is celebrated from March 11-17, 2018. This year’s theme is Green= GO get your eyes tested for
Glaucoma: Save your Sight! The week seeks to raise and increase the awareness of the disease. The World Glaucoma Week is a collaborative project between the World Glaucoma Association and the World Glaucoma Patient Association. It aims to contribute to the elimination of glaucoma blindness by alerting people to have regular eye examination,including examination of the optic nerve head.
Despite the high prevalence of glaucoma and glaucoma-related blindness in Sub-Saharan Africa (SSA), resources for treatment are extremely limited. Medical management of glaucoma is impractical and rarely successful in this population. Issues of availability, affordability and counterfeiting of drugs are major challenges related to medical treatment in this population.6
Trabeculectomy, a surgical operation which lowers the intraocular pressure inside the eye (IOP) in patients with glaucoma remains the standard surgical method of treating glaucoma in Africa but the acceptance rate is low.9,10 Intraocular pressure is reduced by making a small hole in the eye wall (sclera). The fear of surgery, high cost of surgery and the awareness that there may be no improvement in vision after surgery were the most cited reasons for poor acceptability of surgery.11 It has also been reported that many surgeons did not want to perform trabeculectomy because of the well-known complications of the surgery, the negative publicity, late presentation and lack of satisfaction of most patients. In addition, surgical therapy requires highly trained surgeons, well-equipped operating theaters, and extensive long-term follow-up.
This supports a critical need for alternatives which is less invasive and simple. One viable treatment option is the selective laser trabeculoplasty (SLT) which has been shown to be effective in reducing IOP12,13 even in Africans. Other advantages of SLT in low resource settings includes its cost effectiveness when compared to medical therapy. In addition, it is less invasive, safe, convenient and acceptable to patients. Improving glaucoma care in Sub-Saharan Africa requires concerted efforts by everyone: Relevant government agencies, nongovernmental organizations, Ophthalmological Societies in different African countries, glaucoma specialists, and international collaborators.
An important step is creating awareness and screening at risk populations such as those with a positive family history, educatingand re-educating glaucoma patients on the need for regular check-ups and the blinding nature of the disease and managing the disease as appropriate can prevent needless glaucoma blindness even in resource constrained settings of Sub-Saharan Africa.
Dr Olawoye is a Senior Lecturer and Glaucoma Specialist, Department of
Ophthalmology, College of Medicine, University of Ibadan, Nigeria and
CARTA Cohort Seven Fellow