Glaucoma refers to a group of eye conditions that lead to the damage and tissue loss of the optic nerve in the back of the eye, resulting in irreversible vision loss.
What is it?
The optic nerve is a bundle of about 1 million individual nerve fibres responsible for sending visual information from your retina to your brain, where electrical impulses are turned into images.
Vision loss starts in your peripheral/side vision and is so gradual that it could go unnoticed for a long time without early symptoms as warning signs, making regular eye tests crucial.
Glaucoma can be caused by a buildup of a naturally occurring watery fluid within the eye called the aqueous humor. The function of the aqueous fluid is to keep the eye healthy by providing it with nourishment and in the correct shape. Usually, the aqueous fluid drains at the same rate as it is produced.
This build-up of the aqueous fluid can create an increase in the pressure within the eye referred to as intraocular pressure or IOP. This raised pressure may damage the optic nerve leading to vision loss if it is left untreated.
Pressure build-up may occur due to limited outflow of aqueous if the structure that drains the fluid out of the eye is damaged due to a narrowing or closing. The structure that drains the fluid is called the trabecular meshwork; a spongy network of holes found in the angle where the cornea (clear front surface of the eye) meets the iris (colour part of the eye).
Another cause for pressure build-up in the eye can be a result of an over production of aqueous fluid.
Glaucoma can also be a cause of a weakness in the optic nerve structure. In this instance glaucoma can be caused even if your eye pressure falls within the normal range and is sometimes called ‘low tension’ glaucoma.
The normal range for eye pressure falls between 10 to 21 mmHG (millimetres of mercury). However not everyone with higher than normal eye pressure develops glaucoma.
Symptoms
Often there are no symptoms at all, however symptoms of glaucoma may include:
- Blurred vision.
- Sudden severe eye pain associated with severe headaches, nausea, and vomiting.
- Halos or coloured rings around lights.
- Patchy blind spots in the outer edges of your vision or loss of peripheral (side) vision.
Causes and risk factors
Although the exact cause of glaucoma is still unknown, there are risk factors increasing the likelihood of developing glaucoma, including:
- A family history of glaucoma.
- High or low blood pressure.
- High internal eye pressure.
- Diabetes.
- Being over the age of 50.
- Previous eye trauma, such as injury or surgery.
- Near sightedness or far sightedness.
- Long-term usage of steroid medication.
- Having dense cataracts.
- Being of Asian or African descent.
Diagnosis
Regular eye tests are crucial in catching glaucoma in its initial stages. If you have a family history of glaucoma, are over the age of 50, or have any other risk factors for glaucoma, it is important to visit an optometrist regularly.
Your eye care professional will conduct an examination of your eye which may include:
- Checking your visual acuity, which is your ability to see at different distances. This can include recognising letters at varying distances.
- Assessing your peripheral vision with a visual field test (Perimetry), which is your ability to see in your side vision.
- Checking your retina and optic nerve at the back of your eye with an Ophthalmoscope by shining a light into your eye and looking through different lenses or using an Optical Coherence Tomography scan (OCT) which creates a 3D cross section image to see the layers in the retina or take a digital colour photo of the retina.
- Checking the surface of your eye and other structures within the eye with a microscope called a slit lamp.
- Measuring the pressure in your eyes (Tonometry).
- Measuring the thickness of the cornea (Pachymetry).
- Examining the angle where the cornea and iris meets (Gonioscopy).
Treatment
There is no cure for glaucoma and damage caused to the optic nerve with vision loss being permanent. However, modern management regimes see many people avoid future damage and further vision loss. The goal of treatment is to lower the pressure in your eye either through increased fluid drainage or decreased fluid production. Your eye care practitioner will decide which procedure will be best suited to your circumstances.
Treatment options include:
Medications, such as eye drops, to reduce fluid production inside your eye or help to improve fluid drainage.
Laser treatment to improve fluid drainage or reduce the fluid production. There are several different procedures available depending on your condition:
- Selective Laser Trabeculoplasty (SLT) is a treatment to increase the drainage of fluid by stimulating the pigment cells in the trabecular meshwork, causing the body to react and rebuild and work harder.
- Laser Peripheral Iridotomy (LPI) is a treatment to increase the drainage of fluid by making a small hole in the iris, allowing the fluid to drain.
- Cyclodiode Laser Treatment is a treatment to reduce the production of the fluid by destroying the aqueous producing cells in the ciliary body.
- Argon Laser Trabeculoplasty (ALT) is a treatment to increase the drainage of fluid like SLT.
Surgery which can reduce pressure in your eyes by improving the outflow of fluid. There are several different surgery options available depending on your condition:
- Trabeculectomy surgery creates a new permanent drainage channel in your eye to allow fluid to drain, by making a new opening in the sclera (the white part of your eye). The fluid drains into the conjunctiva (the clear membrane that protects the eye) and forms a non-visible little reservoir called a bleb underneath the upper eyelid where the fluid gets reabsorbed into your bloodstream.
- Aqueous shunt is a small tube-like device implanted into the eye to allow fluid drainage out of the eye. Similarly, it creates a bleb underneath the upper eyelid.
- MIGS (minimal invasive glaucoma surgery) is a name given to a range of microscopic implants or devices to help the fluid drain out of the eye through either creating new drainage channels or opening up/widening existing drainage channels. These surgeries are generally done in conjunction with cataract removals, however in some cases they are done as a standalone procedure. Your eyecare practitioner will provide you with the best care options available specific for your condition.
Sustained-Release Drug Delivery: If taking your glaucoma medication becomes problematic, your doctor may suggest a sustained-release drug delivery device, which is a new option available in Australia.
For more information
- Visit Glaucoma Australia.
- Always speak to your GP and eyecare professional about the best treatment options for you.
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