Glaucoma is a group of diseases which damages the optic nerve. The optic nerve carries images from the retina to the brain enabling us to see. In some types of glaucoma, increased pressure inside the eye affects the delicate tissues of the optic nerve. Glaucoma damages nerve fibres, causing blind spots to develop. Often people don't notice these blind areas until much optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results. It is for this reason that glaucoma is known as “the thief of sight”.
Glaucoma is the leading cause of irreversible blindness in the world (67 million affected), especially in older people. Early detection and treatment by your ophthalmologist are the keys to preventing optic nerve damage and blindness from glaucoma.
What Causes Glaucoma?
Mechanical compression and/or decreased blood flow of the optic nerve associated with other factors can lead to glaucoma. Although high eye pressure sometimes leads to glaucoma, as many as 50% of people with glaucoma have "normal" eye pressure.
What Are The Different Types Of Glaucoma?
The main groups are:
1. Chronic glaucoma, e.g. primary open angle glaucoma (POAG)- this is the commonest form and leads to a progressive, painless loss of vision
2. Acute glaucoma- this causes severe pain associated with a red eye and a sudden increase in eye pressure. It warrants emergency treatment
3. Normal-tension or low-tension glaucoma- the optic nerve suffers damage with the resulting visual field loss even though normal intraocular pressures are maintained (between 10-21mmHg of pressure). It is believed that poor blood flow to the optic nerve causes this condition.
4. Exfoliation syndrome is a common form of open angle glaucoma that results when there is a build-up of abnormal, flakey material on the lens. It is commoner in the elderly and in Northern Europe. This material and pigment from the back of the iris can block the drainage system of the eye, causing increased eye pressure. This form of glaucoma responds well to laser (*link to laser treatment below please*) treatment.
5. Pigmentary glaucoma is a condition typically affecting young, nearsighted (myopic), Caucasian males. There is a release of pigment particles into the drainage system of the eye causing blockage, leading to an increase in eye pressure. This form of glaucoma responds particularly well to laser (*link*) and surgery (*link*).
6. Congenital glaucoma- present at birth and very rare.
In most cases, damage to the optic nerve in glaucoma can occur without any symptoms. However, the presence of the following warning signs, indicates that you need a thorough examination by an eye doctor:
Family history of glaucoma
Loss of peripheral (side) vision
Need for frequent changes in glasses
Difficulty in adjusting to a dark room
Sore, reddened eyes
Appearance of halos or rainbows around lights
Severe headaches, nausea and eye pain in rare cases
The symptoms described above may not necessarily mean that you have glaucoma. However, if you experience one or more of these symptoms, contact your eye doctor for a complete examination.
How Is Glaucoma Detected?
Regular eye examinations by your ophthalmologist are the best way to detect glaucoma. Your ophthalmologist will measure your intraocular pressure (tonometry); inspect the drainage angle of your eye (gonioscopy); evaluate any optic nerve damage (ophthalmoscopy); test the visual field of each eye (perimetry). Optic nerve photography and visual field testing are performed at regular intervals to monitor the effects glaucoma has upon the optic nerve and the person's overall vision. The information from these tests provides an indication of the effectiveness of the treatment being used and whether stronger measures may be necessary. Not all these tests are necessary for every person, or at every visit. The object is to determine if glaucoma damage has increased during the time between your visits.
Optic nerve head examination using latest scanning laser ophthalmoscope (SLO) technology
Perimetry (visual fields)- automated visual field measurement with Visual Field Analyzer
Who Is At Risk For Glaucoma?
High eye pressure is the most important risk factor, but alone does not mean that you have glaucoma. Your ophthalmologist will put together many kinds of information to determine your risk for developing the disease. The most important risk factors include age, myopia, African-Caribbean ancestry, family history of glaucoma, past injuries to the eyes, or a history of severe anaemia or shock requiring blood transfusions. Your ophthalmologist will consider all these factors before deciding if you need treatment for glaucoma, or whether you should be monitored regularly as a glaucoma suspect to detect the early signs of damage to the optic nerve.
“Cupping”- damage to the optic nerve head (optic disc) causing enlargement of central cup (pale area
The treatment for glaucoma depends upon the nature and severity of each case. As a rule, glaucoma cannot be cured, but it can be controlled. Eye drops, tablets, laser treatment and surgical procedures are used to prevent or slow further damage from occurring. With any type of glaucoma, periodic examinations are very important to prevent vision loss. Because glaucoma can worsen without your being aware of it, your treatment may need to be changed over time.
Topical medication- drops
Treatment with drops to reduce eye pressure is a proven method of preserving vision in glaucoma.
There is a wide variety of drops on the market so that a large range of different glaucoma conditions and patient preferences can be addressed.
The latest group of drops is the Prostaglandin analogues (e.g. Xalatan, Travatan, Lumigan), which are very effective and taken only once in the evening.
Side-effects from some eye drops may include a stinging sensation, red eyes, blurred vision, headaches, reduction in pulse and heart rate or wheezing. Side-effects from pills may include tingling of fingers and toes, drowsiness, loss of appetite, bowel irregularities, kidney stones, anemia or bleeding.
Laser surgery treatments may sometimes be effective alone or as additional therapy to drops.
Trabeculoplasty is laser treatment to encourage drainage to reduce pressure within the eye when treating open-angle glaucoma.
Selective Laser Trabeculoplasty (SLT) - this is an advanced technology and promotes drainage of fluid without damaging the delicate tissues of the eye.
Iridotomy is laser treatment to create tiny holes in the iris to prevent obstruction of fluid outflow.
Cyclodiode laser- a very effective and safe way of reducing eye pressure long-term in moderate to advanced cases of glaucoma. It is performed in the operating theatre under local anaesthetic as a day case procedure.
The SLT Laser System
Cyclodiode laser treatment
This is the best way of achieving a low eye pressure for a long time. When operative surgery (trabeculectomy or glaucoma drainage tube insertion) is needed to control glaucoma, your ophthalmologist will use miniature instruments under microscopic viewing to create a new drainage channel for the aqueous fluid to leave the eye. The new channel helps to lower the pressure inside the eye. Complications of glaucoma surgery are rare, but as with any surgery they can occur. Surgery will be recommended only if your ophthalmologist feels that it is safer to operate than to allow optic nerve damage to continue.
The procedure can be performed either as an in-patient or day-case procedure
Local or general anaesthetic can be used
The latest anti-scarring drugs are used to preserve the function of the new drainage channel for longer
You will stop using your glaucoma drops, but will start using antibiotic and anti-inflammatory drops for a short period of time while the healing process occurs
Careful post-operative follow-up with the ophthalmic surgeon will ensure that the eye pressure is well controlled
Minimally invasive glaucoma surgery (MIGS)