Glaucoma

What is Glaucoma?

Glaucoma is one of the leading causes of blindness worldwide.

Glaucoma refers to a group of eye conditions that damage the optic nerve, which is crucial for good vision.

Vision loss due to Glaucoma is permanent, therefore it is important to have regular eye exams that include measurements of your eye pressure to detect this early.

If Glaucoma is diagnosed early, vision loss can be slowed or prevented. If you have been diagnosed with the condition, you will generally need treatment for the rest of your life.

What Causes Glaucoma?

Glaucomatous damage to the optic nerve is often caused by abnormally high pressure in the eye.

The optic nerve transmits the images we see back to the brain for interpretation, these delicate nerve fibres are easily damaged when the intraocular pressure is elevated.

Other causes of Glaucoma include decreased blood flow to the optic nerve caused by narrowing of blood vessels that nourish the optic nerve or constrictions of these vessels. Some medications can also cause glaucoma.

What are the Types of Glaucoma?

Glaucoma can be categorised as follows:

Open-Angle Glaucoma

Open-angle Glaucoma is the most common type of Glaucoma also called primary or chronic Glaucoma

• The angle between the iris and cornea (structures in front of the eye) is wide and open
• This type of glaucoma occurs when the eye’s drainage system becomes clogged and gradually increases the pressure inside the eye
• Usually has no warning signs

The effects are so gradual that patients may not notice a change in vision until the condition is at an advanced stage.

Closed Angle Glaucoma

Closed Angle Glaucoma is a less common form of Glaucoma. 

• The angle between the iris and the cornea is narrow or closed.
• It occurs when a portion of the entire drainage angle becomes anatomically closed so that the aqueous fluid within the eye cannot drain smoothly out of the eye through the trabecular meshwork. This inability to drain can cause a sudden build-up of pressure in the eye. 

People with small eyes, or who are longsighted, are predisposed to developing angle-closure Glaucoma because they tend to have narrow drainage angles. 

Acute Angle-Closure Glaucoma

Acute Angle-Closure Glaucoma is an eye emergency, which requires immediate medical attention and treatment.

Patients may complain of the following symptoms: 

• A severe headache, associated with
• Severe eye pain
• Nausea and vomiting
• Blurred vision
• Halos around lights
• Eye redness

In addition, the high intraocular pressure leads to corneal swelling (oedema), which causes the patient to see halos around lights.

It is very important for patients with the above symptoms to seek urgent medical attention as they need urgent treatment to lower their eye pressure, or the damage may be permanent. 

Eye surgery for Acute Angle-Closure Glaucoma involves an ophthalmic surgeon creating a small hole in the iris with a laser (laser iridotomy) to allow the fluid to resume draining into its normal outflow channels.

Normal-Tension (Pressure) Glaucoma

Normal-Tension Glaucoma or low tension Glaucoma is a type of Glaucoma where the optic nerve is damaged despite intraocular pressure being normal. 

Congenital Glaucoma 

This type of Glaucoma is seen in babies and often runs in families. It is caused by improper development of the eye’s drainage canals before birth.

Other Glaucomas

Other types of Glaucoma include:

• Pigmentary Glaucoma
• Secondary Glaucoma
• Pseudoexfoliative Glaucoma
• Traumatic Glaucoma
• Neovascular Glaucoma
• Irido-Corneal Endothelial Syndrome (ICE)

Who is at Risk of Glaucoma? 

Glaucoma can occur at any age but is more common in middle-aged people. Some people have a higher than normal risk of getting Glaucoma. This includes people who:

• Aged 40 or over
• Have a family history of Glaucoma
• Have high eye pressure
• Are of African or Hispanic heritage
• Are farsighted (Hyperopia) or near-sighted (Myopia)
• Have corneas that are thin in the centre
• Have diabetes, migraines, poor blood circulation or other general health problems that affect the eye
• Have had an eye injury

People with more than one of the above risk factors have an even higher risk of Glaucoma, and they should consult an ophthalmologist at the age of 40 for a comprehensive eye examination.

Glaucoma Diagnosis

Open-angle Glaucoma gives few warning signs. Some people may observe patchy blind spots in their peripheral or central vision before permanent damage occurs. 

A regular Eye Examination is a key step in detecting Glaucoma early enough to successfully slow or prevent vision loss. 

As mentioned, people with any risk factors of Glaucoma should have an ophthalmologist perform a Comprehensive Eye Examination that includes:

• eye pressure measurement
• gonioscopy (assessing the anterior chamber drainage pathway)
• dilated fundus examination
• imaging of the optic nerve head and 
• visual field test

Sometimes, patients may be identified as potential Glaucoma sufferers through a routine Eye Examination with an optometrist. 

It is important to maintain regular follow up with your ophthalmologist once a diagnosis of Glaucoma is made.

Treatment Options

Eye Drops

At the early stage of the disease, patients can usually be managed medically with eye drops that lower the eye pressure. 

It is important to consult an ophthalmologist regarding the eye drops as some of them have significant side effects. 

Laser Trabeculoplasty

Laser Trabeculoplasty is often used to treat open-angle Glaucoma. 

The laser is aimed at the trabecular meshwork, where fluid drains from the eye. This surgery opens the clogged areas and makes it easier for fluid to flow out of the eye.

There are two types of laser trabeculoplasty surgery:

• Argon Laser Trabeculoplasty (ALT) - During ALT surgery, a laser is targeted at the trabecular meshwork to improve fluid drainage out of the eye
• Selective Laser Trabeculoplasty (SLT) - SLT is similar to ALT but uses a laser of different frequencies and is generally less damaging to cells in the eye

The aim of these procedures is to lower eye pressure by increasing the drainage of fluid. It does this by opening up the clogged areas in the meshwork, making it easier for fluid to flow out of the eye.

Minimally Invasive Glaucoma Surgery or MIGS

Minimally Invasive Glaucoma Surgery or MIGS involves the insertion of micro stents into the drainage angle of the eye during cataract surgery.

This procedure has been shown to reduce eye pressure and is very safe. 

Trabeculectomy 

This is a surgical procedure that involves creating a drainage pathway out of the eye, into a 'bleb' under the conjunctival, usually at the top of the cornea. It is used to treat advanced glaucoma.

Tube Shunt

This procedure uses an extremely small tube to divert fluid out of the eye. As only controlled and precise amounts of fluid are let out, the internal pressure of the eye is maintained at a more steady level.

These advanced Glaucoma drainage surgeries can be an option to control your pressure and any consequential damage caused by the disease.

In some cases it will be necessary to refer patients to Ophthalmologists with sub-specialty for ongoing management.