Glaucoma is a group of eye disease causing optic nerve damage. The optic nerve is responsible for transmitting images from the retina which is the specialized light sensing tissue to the brain.
Prof. Adeola Onakoya, Head of Department of Opthamology, Lagos University Teaching Hospital (LUTH), defined the optic nerve as “the nerve that link the brain to the eye; the optic nerve is like a cable at the back of the eye that connects to the brain, It enables the brain to interpret what it sees”, Adeola explained that when this nerve is diseased it becomes glaucoma.
It is often associated with the build up of pressure inside the eye and/or decreased blood flow of the optic nerve, although high eye pressure also referred to as intraocular pressure or ocular hypertension sometimes leads to glaucoma. People can also develop glaucoma with normal eye pressure, this condition is simply referred to as “normal tension glaucoma.”
Onakoya said,“Normal tension glaucoma simply means when the pressure is within the normal range yet one has glaucoma. There are some people when you are treating them, the pressure is still normal but the glaucoma progresses. It means there are some other reasons, the reason is simple, it means that these set of people developed glaucoma aside from the pressure and that has to do with the blood flow in the eye”. Normal tension glaucoma is determined by a comprehensive eye exam and visual field testing.
According to the NEI -funded Ocular Hypertension Treatment Study, 4-5 to 9-4 percent of Americans age 40 or older have ocular hypertension, which increases their risk of developing glaucoma. Researchers have estimated that ocular hypertension is 10-15 times more likely to occur than primary open angle glaucoma, the most common type of glaucoma. The global target of World Health Organisation (WHO) in vision 2020 which is the “right to sight “ is ultimately to reduce blindness prevalence to less than 0.5 in all countries or less than 1% in any community.
Glaucoma is referred to as “the silent thief of sight” This is because it slowly damages the eye and causes irreversible loss of vision to the sufferer. This disease affects more than 2.7 million people in the United State and more than 60 million world wide. WHO in 2000 stated that about 314 million people are visually impaired while 45 million of them are blind with 87% of the visually impaired living in the developing countries.
The National Eye Centre, Kaduna, Nigeria a collaborating center of WHO carried out a study to find out the prevalence of glaucoma in Nigeria from 1998-2006. In their study, age distribution showed that the prevalence of glaucoma is higher between ages 40 years and above with 3202 patients representing 43%, followed by age 31 – 40 with 2792 patients representing 37%.