Glaucoma is a leading cause of blindness in Australia.
In glaucoma, the optic nerve of the eye is damaged by rising pressure. If detected early, treatment can prevent or reduce vision loss.
Glaucoma is a group of diseases in which the internal pressure of the eye (the Intraocular Pressure or IOP) rises gradually or suddenly, resulting in damage to the optic nerve. The optic nerve is a vital structure for vision, as it transmits visual signals from the nerve fibre layer at the back of the eye (the Retina) to the visual centre in the brain, much like an electrical cable. When the intraocular pressure around it is too high, the optic nerve begins to lose its fibres, leading to the gradual or sudden loss of vision.
The eyeball is a closed system full of fluid (called aqueous humor). In the normal eye, this fluid is produced at a rate that is equal to the rate at which it is drained out of the eye, so that the pressure is maintained at a stable level. In glaucoma, there is a disturbance of this equilibrium, usually due to impaired drainage of the fluid from the eye. This reduced drainage results in increasing pressure in the eye, and damage to the optic nerve.
There are different types of glaucoma.
1. Open-angle glaucoma
The commonest type of glaucoma is open-angle glaucoma. This type of glaucoma is often “silent” in its early stages, with no detectable symptoms such as pain or vision loss. This type of glaucoma typically is more common with increasing age, and particularly in those with a family history of glaucoma. It is often detected during a routine eye check with the optometrist or ophthalmologist.
2. Normal-pressure glaucoma
This is a sub-type of open-angle glaucoma, whereby the measured eye pressure is within the normal range (10-21mm Hg) but progressive damage to the optic nerve still occurs. This is why the intraocular pressure measurement is not the best guide as to whether a patient has glaucoma. In fact, the intraocular pressure can fluctuate in ever patient from hour-to-hour during the day. The appearance and health of the optic nerve, for a given pressure in any patient, is the more important indicator of whether a patient has glaucoma.
3. Closed-angle (or narrow-angle) glaucoma
This type of glaucoma is much rarer, but potentially more damaging than open-angle glaucoma. In this glaucoma, there may be a sudden physical blockage of the drainage angle of the eye, which can result in a quick fluid build-up in the eye and a rapid rise in the pressure.
Acute angle-closure glaucoma (AACG) is an emergency that can lead to rapid blindness if not detected and treated appropriately. In AACG, the pressure may suddenly rise to extremely high levels, leading to severe eye pain, blurry vision, haloes around lights, headache, nausea and vomiting. These attacks often occur in the middle of the night, when the iris of the eye dilates and contributes to further narrowing of the drainage angle of the eye.
Chronic closed-angle glaucoma is more gradual but can be more resistant to treatment than open-angle glaucoma.
4. Secondary glaucoma
This glaucoma results from another eye disease. These include previous eye trauma, certain medications (particularly long-term steroids), and specific eye conditions like pseudo-exfoliation or pigment dispersion syndromes. These will be detected by the ophthalmologist.
5. Congential glaucoma
This is a very rare glaucoma that develops in infants and young children, and often inherited. It is a difficult condition to treat, and often leads to blindness if not detected and managed early.
Factors which increase the risk of developing glaucoma include:
- Increasing age (particularly >40yo)
- Family history, especially direct family (parents, siblings)
- High myopia (short-sightedness)
- Ethnicity (African-Caribbean or Hispanic)
- History of migraine
- Heart disease and hypertension
1. Open angle glaucoma
Most patients will not know that they have this type of glaucoma as it does not cause any noticeable symptoms until very late in the disease. There is never any pain in this glaucoma, just progressive visual loss. Usually, the peripheral vision is lost first, and in the later stages of disease, the central vision is lost. Patients with very advanced glaucoma have only a small central island of vision remaining (“tunnel vision”), and in the final stages even this is lost, leading to complete blindness.
2. Closed angle glaucoma
Acute angle closure manifests with severe eye pain, headaches, blurry vision and haloes around lights, nausea and vomiting. There are usually no warning symptoms prior.
Chronic angle closure presents like open angle glaucoma, with gradual vision loss but no pain.
A diagnosis of glaucoma is made after thorough examination and testing, usually over a period of time. Multiple areas need to be assessed simultaneously, including:
- Intraocular pressure measurements
- Optic nerve health
- Visual field measurements
The assessment of the optic nerve is the most important and has been greatly enhanced with the use of advanced technology such as OCT scans, which can detect optic nerve changes well before the naked eye can.
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Like high blood pressure, there is no cure for glaucoma. The aim of treatment is to lower the internal eye pressure to protect the optic nerve and slow the rate of visual loss in the eye.
1. Eye drops (Topical therapy).
In most patients, treatment with pressure-lowering eye drops is enough to control their glaucoma, without the need for laser or surgery. There are various types of glaucoma drops, which work in different ways. Most patients only need one type of eye drop to control their glaucoma, but some will require 2 or 3 different types of eye drops in combination to adequately control their pressure. Pressure-lowering eye drops are generally safe, easy to use, and well-tolerated. However, side-effects can still occur, and the Dr Then will discuss the specific side-effects of each particular drop before commencing treatment. Once on eye drops, they are generally required for the rest of the patient’s life.
2 .Eye laser.
There are 2 type of laser used to treat glaucoma:
SLT (Selective Laser Trabeculoplasty). This is generally considered a secondary therapy for open-angle glaucoma, where eye drops alone have not been successful in controlling eye pressure. After SLT, some patients may no longer require eye drops. SLT aims to increase the fluid drainage from the eye, by lasering the drainage meshwork in the angle of the eye. It is performed in the clinic, and is considered a safe and well-tolerated procedure. It may require more than one session to achieve adequate pressure control.
YAG laser PI (peripheral iridotomy). This is used to treat closed-angle or narrow-angle glaucoma. It creates extra drainage ports in the iris (coloured part) of the eye, to allow easier flow of aqueous humour within the eye. It is used in both the acute and chronic forms of closed angle glaucoma. It is performed in the clinic, and is also a safe and well-tolerated procedure.
3. Glaucoma surgery. This is rarely required these days in the management of glaucoma but will be used if eye drop therapy or laser therapy fails. This surgery aims to create larger drainage ports in the eye either through an opening in the outer eye tissue (trabeculectomy) or through a drainage tube that passes from the inside to the outside of the eye (tube-filtration surgery).
MIGS is a more recent advancement in the surgical control of glaucoma.
MIGS are a group of micro-surgeries that use small implants inserted into the drainage angle of the eye to reduce the internal eye pressure and help with long-term glaucoma control. There are at least 3 different types of MIGS available for use in Australia. Dr Then currently uses the iStent inject TM by Glaukos.
MIGS is used in patients with mild to moderate open-angle glaucoma who have already tried eye drops for their glaucoma. MIGS may reduce the need for eye drop therapy in certain patients with glaucoma. MIGS is usually performed at the same time as cataract surgery but has also been approved as a stand-alone procedure. If you are eligible, Dr Then will discuss this procedure with you in more detail.
When patients develop glaucoma, they will require long-term monitoring to ensure that their treatments stay efficient over their lifetime. It is recommended that most patients have a regular check every 6 to 12 months, depending on the severity and stability of their glaucoma. More severe forms of glaucoma may require more frequent checks.
At each check-up, all of the important glaucoma parameters (eye pressure, optic nerve appearance, visual fields) are assessed, to ensure that there has been no deterioration in the glaucoma despite therapy. If there is, then the therapy is increased, either with more eye drops, or consideration of laser or surgery.
As vision lost cannot be restored, prevention of vision loss is the key. Early detection of change or progression is very important in the long-term management of glaucoma.