By Dr Neeraj Jain, MD, DNB, MNAMS (Ophthalmology)
Glaucoma constitutes a diverse group of disorders associated with elevated intraocular pressure that culminate in a characteristic pattern of optic nerve atrophy, loss of visual field eventually leading to blindness. Glaucoma is a dangerous eye condition because it frequently progresses without obvious symptoms, and hence is frequently referred to as ‘the sneak thief of sight.’
What is glaucoma?
In the front of the eye there is a space called the anterior chamber. A clear fluid flows continuously in and out of the chamber and nourishes adjacent tissues. The fluid leaves the chamber at the angle where the cornea and iris meet. (See diagram below.) When the fluid reaches the angle, it drains through a spongy meshwork. Due to the resistance offered by the meshwork, outflow is less than inflow. The difference induces pressure build-up in the eye, known as intraocular pressure (IOP). Poor or blocked drainage can raise the IOP to unsafe limits. This is one of the main factors for damage to the optic nerve commonly known as glaucoma.
What are the types of glaucoma?
There are four major types of glaucoma:
Open angle glaucoma – when the fluid reaches the angle, it passes too slowly through the meshwork drain due to underlying pathology.
Angle closure glaucoma – in this variety the iris blocks the angles and there is no way out for the fluid.
Congenital glaucoma – the basic cause is malformed channels or abnormal anatomy of outflow.
Secondary glaucoma – some other cause will lead to a block in outflow at various levels.
What are the signs and symptoms for the disease?
Glaucoma is typically associated with painless and progressive loss of vision that may escape detection by the patient or by the attending family doctor for long periods.
Open angle glaucoma generally has no signs and symptoms. The majority of the people do not find anything wrong with their eyes when it starts; some may have mild headache, heaviness of the eyes, fast progression of reading glasses and a few other vague symptoms. Mostly vision stays normal, and there is no pain. Without treatment, people with glaucoma will slowly lose their peripheral (side) vision.
People with angle closure glaucoma initially perceive coloured halos around the light, generally at evening or night time. Any acute attack of angle closure glaucoma is very painful and the patient will have photophobia, red eye, blurry vision associated with nausea, vomiting and severe headache. This is an emergency situation and can lead to vision loss in a few hours if left untreated.
Congenital glaucoma is associated with high IOP since birth; a newborn may show watering, redness of the eyes and photophobia. Later he may have large corneas which become opaque in the succeeding months.
Secondary glaucoma has various presentations depending on the underlying disease which leads to the development of glaucoma.
How is it diagnosed?
Glaucoma is a chronic, slowly progressive disease. The optic nerve gradually becomes damaged over a period of 5 to 30 years. The loss of nerve fibres occurs so gradually that the decrease in vision is usually not noticed until over half of the nerve fibres have died.
It often isn’t until both eyes have lost a great deal of vision that the afflicted person recognizes the loss, and most of the time it’s too late.
A thoughtful, thorough examination which takes into account a patient’s family background (since glaucoma seems to be hereditary), intraocular pressure, angle anatomy (gonioscopy), visual field, and the condition of the optic nerve will allow the treating doctor in most cases to accurately determine whether a person has glaucoma. Sometimes multiple visits are required to establish the diagnosis in borderline cases. New techniques have added other dimensions in accurate diagnosis and meticulous monitoring of the progression of the optic nerve atrophy.
Who is at risk for glaucoma?
Glaucoma can affect anyone irrespective of their age. Some people are at higher risk than others.
They include:
Africans over age 40, everyone over age 60, especially Mexican Americans
People with a family history of glaucoma
Hypertensive and diabetic patients
Myopia and history of injury to the eye.
A word of caution
Long-term epidemiological studies have shown that glaucoma has a different long-term course in people of African ethnicity. Their glaucoma progresses faster than that of other races, the blindness rate is higher than other races and the surgical failure rate is higher when compared to people of other ethnicities. So it is advised worldwide that they should have more frequent eye evaluations for glaucoma.
What is the treatment?
Once this basic determination has been made, the doctor will devise an appropriate treatment plan. He or she will then carefully monitor the optic nerve appearance, visual field and intraocular pressure to determine if any further damage is being sustained. Unfortunately approximately 10% of people with glaucoma who receive proper treatment still experience loss of vision.
Glaucoma treatments include medicines, laser, conventional surgery, or a combination of any of these. While these treatments may save the remaining vision, they do not improve the sight already lost from glaucoma.
Medicines – Medicines, in the form of eye drops or pills, are the first line treatment for any type of glaucoma. Medicine reduces intraocular pressure either by helping better drainage of fluid or suppressing the formation of fluid. Patients may need one or more than one combination of drugs depending on the severity of the glaucoma.
Surgery – by surgery a bypass is created to permit alternative drainage of fluid; this allows the intraocular pressure to fall below the required level. There are many forms of surgery available, but surgery has its own risks and chances of failure too. Some people may need more than one surgery or use of a drainage device.
Lasers – lasers are other non-invasive tools to help in treatment. Lasers can be used as a preventive measure in angle closure glaucoma or as a part of the treatment in open angle glaucoma. Lasers can be used as a primary modality as well as adjunctive to the medical or surgical treatment.
It is important to note, however, that treatments cannot be generalized. Each patient, regardless of race, should continue to be evaluated on the individual state of his or her disease, with a target pressure and treatment plan unique to each patient. Since glaucoma is a chronic condition, it must be monitored for life. Strict treatment compliance always helps.