Glaucoma refers to a group of diseases that cause chronic progressive optic neuropathy resulting in characteristic optic nerve damage, retinal nerve fibre layer defect and visual field defect. In simple English, glaucoma damages the nerve for vision (called the optic nerve) resulting in irreversible loss of vision. This damage takes place over a long time and is asymptomatic until the advanced stage where vision loss occurs, hence glaucoma is called the silent thief of sight. Glaucoma is the leading cause of irreversible blindness worldwide and the second leading cause of blindness (both reversible and irreversible).
Damage to the optic nerve results in a characteristic cupping of the optic nerve head, this cupping is the defect seen when looking at the optic nerve head during fundoscopy. Loss of vision initially involves the peripheral field of vision with the central vision being the last to be affected. In other words, glaucoma can cause people to see things that are straight ahead of them but they do not to see things in their peripheral view when they are looking straight ahead.
Glaucoma can be classified based on various criteria such as age of onset (congenital or acquired), gonioscopy (open and closed angle), aetiology (primary or secondary). Although glaucoma can affect all age groups (from birth to the elderly), it is commoner in people from 40 years and above. Other risk factors for glaucoma include high intra ocular pressure, black race, family history of glaucoma and myopia. Normal intra ocular pressure is assumed to be 10 – 21 mmHg, glaucoma can occur even when intra ocular pressure is normal.
Treatment of glaucoma may be medical, laser or surgery. Treatment is not curative, the goal of treatment is to ensure that the disease does not progress, as such vision is maintained at the level it was when diagnosis was made. The implication is that the diagnosis of glaucoma is best made while vision is still good as vision cannot be improved or restored once it is lost to glaucoma.
The essence of this write up is to sensitize you to the fact that there is an eye disease that causes irreversible blindness without giving any symptom, therefore ensure that once a year you see an ophthalmologist (eye doctor) to have your eyes examined for glaucoma now that you are seeing.
Dr Olushola Samuel Olajide, senior registrar, Department of Ophthalmology, Babcock University Teaching Hospital, Ilishan Remo, Ogun State, Nigeria.
