Glaucoma describes a group of diseases which cause damage to the optic nerve, eventually leading to blindness if left untreated. It is the most common cause of preventable blindness in Australia. The optic nerve transmits all visual information from the eye to the brain for further processing. Damage to the optic nerve leads to insidious and progressive blindness. There are several risk factors for glaucoma however the most common and only modifiable risk factor remains increased pressure within the eye (termed intraocular pressure, or IOP) – akin to overinflating a soccer ball. The loss of vision is painless and usually very gradual, with a significant amount of peripheral vision lost before patients become aware of their tunnel vision. Unfortunately, because nerves have a very limited capacity to repair themselves, vision loss from glaucoma is irreversible. Therefore regular testing is required to identify glaucoma development and progression.
Types of Glaucoma
Glaucoma is generally divided into categories according to the eye’s anatomic appearance. Management varies depending on the type and severity of glaucoma and response to previous treatment.
- Open Angle Glaucoma is the most common form and accounts for 90% of glaucoma cases in Australia. Elevated pressure within the eye is painless and irreversible visual loss is gradual.
- Closed Angle Glaucoma is less common but progression is usually more rapid with possible episodes of sudden high pressure causing significant ocular pain.
Risk Factors for Glaucoma
Glaucoma is more common in patients with:
- Elevated intraocular pressure – the leading risk factor and the only clinically proven modifiable risk factor
- Family history – the risk of glaucoma is significantly elevated if siblings or parents are affected with glaucoma
- Age – the risk of glaucoma increases as we get older
- Race – some ethnicities are more likely to have certain types glaucoma
- Other less common associations include people with far-sightedness or near-sightedness, steroid exposure, and patients with obstructive sleep apnoea, diabetes, poor circulation and migraines
Glaucoma is notoriously known as the “thief in the night” because the vast majority of patients have significant and irreversible visual loss before they develop any symptoms. Some patients may notice:
- Loss of visual field or a tunnel-vision effect – this represents damage to the peripheral visual field due to glaucoma. If left untreated, the eye will become blind following involvement of the central vision.
- Severe ocular pain – this is rare and a sign of possible Closed Angle Glaucoma.
Since people with glaucoma will usually have no symptoms, regular eye examinations are the best way to detect glaucoma. Diagnosis is usually made by the specialist following detailed history, examination and investigation. During glaucoma evaluation the following tests may be performed
- Pachymetry – this is measurement of the central corneal thickness using a handheld device takes only a few seconds to perform
- OCT – this is a harmless laser-guided scan of the optic nerve, looking for any existing glaucoma damage or progression
- Visual Field – this test assesses the area that each eye can see and is used to detect any visual field loss
While glaucoma cannot be prevented, once diagnosed, the problems it causes can be slowed down significantly with treatment. Treatment is not curative, therefore once the decision to start treatment has been made, it is usually continued for life. The goal of treatment is to lower the pressure within the eye to ensure no further damage to the optic nerve occurs. This can be achieved through several ways
- Medical Treatment – this involves eye drops and is usually first line. There are several different classes of eye drops that lower the eye pressure and often a combination of drops may be necessary. The doctor will tailor your treatment plan to ensure the most effective pressure lowering result while minimising any side effects
- Laser Treatment – several lasers can be used to assist in lowering the eye pressure depending on the type of glaucoma you may have. In general, lasers can be used as an alternative to eyedrops or to augment your eyedrop treatment.
- Surgical Treatment – several glaucoma operations are available, ranging from tiny stents placed inside the eye to improve the outflow of fluid through its normal channels, or valves fashioned in the wall of the eye (‘trabeculectomy’) to bypass the usual drainage channels. Occasionally, a special tube/shunt device is used if there is inadequate pressure control after all medical and laser options have been exhausted.
What Can You Do?
To help detect or slow the progression of glaucoma, patients are advised to:
- Maintain regular eye exams – due to its insidious nature, detection or progression of glaucoma can only be confirmed following detailed history, examination and investigations. It is important to maintain regular eye exams to ensure appropriate treatment is commenced in a timely manner
- Ensure compliance with the recommended treatment plan – best results will require diligence, and by adhering to the prescribed plan, the doctor will be able to more reliably assess the response to treatment
Glaucoma is a leading cause of blindness in Australia with many patients unaware they are at risk or have the disease, so regular eye exams are recommended. Early detection and treatment can prevent or delay further vision loss.