A comprehensive guide to glaucoma including its definition, symptoms, treatment, and prevention

Glaucoma is an eye condition that can lead to permanent vision loss and blindness. It is usually caused by a build-up of pressure in the eye, which damages the optic nerve. This affects the way the eye processes visual information and gradually causes vision loss.   

The condition is most common in people over 60 but can affect anyone. It progresses gradually meaning its symptoms are difficult to notice. For this reason, it is important to stay informed about glaucoma and to attend routine eye examinations with an optometrist. 

Glaucoma definition

Glaucoma is a condition that affects the optic nerve, through which the eye communicates visual information from the retina to the brain. When the eye fails to drain fluid correctly pressure builds within the eye and pushes against the retina and optic nerve. This can lead to permanent vision loss. In some cases, glaucoma can occur without a build-up of pressure in the eye, usually when the optic nerve is damaged in other ways.  

Various factors can make you more likely to develop glaucoma, including your age, family history, and ethnicity. Older people are at greater risk of getting glaucoma, as are people of African and Asian descent (Tham et al, 2014). There are also several genes linked to the condition so if you have a close relative with glaucoma you are more likely to develop it yourself.  

Different Types of Glaucoma 

There are several different types of glaucoma.  

The most common by far is open-angle glaucoma, which accounts for approximately 90% of all cases. In this type of glaucoma, the drainage angle in the eye becomes partially blocked, leading to a gradual pressure build-up in the eye which progressively causes vision loss. In these cases, the effects of the condition progress very slowly and usually there are no symptoms in the early stages.  

Acute angle closure is a much less common form of glaucoma but can cause sudden damage to the optic nerve leading to permanent vision loss. In cases of acute angle closure glaucoma, the eye's drainage angle becomes completely blocked, causing a rapid build-up of pressure. In this type of glaucoma, the effects take place rapidly, so it is vital to seek medical attention as soon as you notice its symptoms (see below).  

Chronic angle-closure glaucoma develops gradually like open-angle glaucoma and so doesn’t have any symptoms at first. However, people with chronic angle-closure glaucoma may develop an acute attack, which requires immediate medical attention.  

Other types of the condition include secondary glaucoma in which an underlying condition causes the drainage angle to become partially blocked. Another rare form is childhood glaucoma in which an abnormality leads to higher eye pressure. This occurs when the eye develops differently or is injured; it also presents with slightly different symptoms than other types of glaucoma. 

Detection of glaucoma

Glaucoma is a condition that develops gradually and causes irreversible eye damage. However, once diagnosed it can be treated to prevent vision loss from getting worse. This means that early diagnosis through regular eye exams is a crucial part of dealing with glaucoma. 

The condition can be diagnosed during a routine eye exam using several different tests. Most commonly, glaucoma is diagnosed using an eye pressure test, while a visual field test may be used to judge the severity of vision loss.  

During an eye pressure test, the optometrist will numb the eye using medicated drops and then use an instrument called a tonometer to measure the pressure. The test is painless and noninvasive.  

A visual field test checks to see if glaucoma has damaged any areas of your vision. There are different versions of the test but usually, you will be asked to focus on a specific point while flashes of light are displayed. Using a buzzer or another method you will indicate whether or not you have seen an individual flash. 

Gonioscopy is another way to detect glaucoma. Using a specialized lens and a slit lamp microscope, an optometrist will examine the eye’s drainage angle to see whether it is blocked.  

Your optometrist may also want to assess damage to the optic nerve. Two tests that can do this are the slit lamp test and Optical Coherence Tomography (OCT). Slit lamp tests work by using a kind of microscope and a bright light, while OCT scans use a special kind of light to create a cross-sectional image of the inner eye. OCT scans are extremely detailed and allow optometrists to diagnose glaucoma in the earliest stages.  

Symptoms of glaucoma  

The most common type of glaucoma (open-angle) does not initially present any symptoms. Over time you may notice blurred vision, that typically affects the edges or peripheries first and gradually affects your central vision as well. This gradual visual impairment often leads to experiencing ‘tunnel vision’ in which your field of vision narrows.  

Acute angle closure glaucoma is much less common and requires immediate medical attention. This type of glaucoma will usually have quickly developing symptoms including eye pain, red eyes, severe headache, nausea, blurred vision, and coloured halos around lights.  

Even more so than with adults, it is difficult for children to detect the early signs of glaucoma. The type of glaucoma to affect children is also sometimes different to that affecting adults and has different symptoms. As a parent or caregiver, there are some signs you can look out for. These include frequently tearing or watery eyes, cloudy corneas, sensitivity to light, redness in the eye and one eye appearing larger than the other. 

As glaucoma progresses it can lead to complications including permanent vision loss and blindness. For both adults and children, it is usually diagnosed in a routine eye exam because of its lack of symptoms in the early stages. Staying up-to-date with eye exams and looking out for early warning signs is the best way to protect yourself against glaucoma.  

Treatment options for glaucoma

Treatment options for glaucoma depend on which type you have and how far advanced it is. For open-angle glaucoma medicated eye drops are usually prescribed first and laser treatment or surgery are considered as secondary measures.  

Eye drops work by reducing the build of pressure in the eye to try and stop the damage being caused to the optic nerve. There are different kinds of eye drops for glaucoma some of which work by reducing the amount of fluid the eye produces and others that help the eye to drain fluid properly. These medications do come with a variety of side effects that can cause significant discomfort, so always make sure to discuss them with your doctor or optometrist.  

Laser treatments also offer an effective way to treat glaucoma, but are usually only recommended after eye drops have been prescribed. These treatments are also often used in conjunction with a specific type of eye drop. 

Trabeculoplasty is used to treat open-angle glaucoma and works by carefully clearing the drainage angle of the eye using a laser. This option is usually effective in reducing eye pressure and is minimally invasive. While there is a risk of increased eye pressure or infection, these complications are rare.  

Iridotomy is a slightly different laser treatment, which is used to treat angle-closure glaucoma. In this procedure, a new drainage channel is created in the iris to bypass the blocked drainage angle, allowing excess fluid to flow out and reducing eye pressure. Acute angle-closure glaucoma requires urgent medical attention and is usually treated with medicated eye drops first, while iridotomy is considered a secondary option. This procedure is also low risk but can also lead to complications like increased eye pressure and blurred vision.  

Glaucoma can also be treated using a surgical option called trabeculectomy. In this case, a tiny hole or flap is created through which the eye can drain fluid. This is also an effective way to reduce eye pressure but is less common because it is considered to be slightly more invasive. 

No one treatment is the best for everyone and it is best to discuss your options in detail with a qualified optometrist. Find your local specialist!

Preventing glaucoma

Because glaucoma can cause severe vision loss and blindness, it is important to find the best ways to prevent it and minimise its effects. Improving your overall health through lifestyle changes, staying up-to-date on your eye health with regular eye exams and knowing whether you have an increased risk of glaucoma can help you to prevent the condition or its most damaging effects. 

Your eyes are a part of your general health and are affected by diet, exercise and unhealthy habits like smoking. Looking after your eyes and health can help to minimise the risk of conditions like glaucoma. For example, people with diets high in fruits and green leafy vegetables are less likely to develop glaucoma (American Academy of Ophthalmology, 2021). Additionally, regular exercise can help to reduce eye pressure, which can minimise the effects of the condition (American Academy of Ophthalmology, 2021). Some supplements have been linked to improved eye health that may help to slow down myopia development, but much of the research is inconclusive. It is a good idea to discuss your diet, exercise and general health with your optometrist, especially if you are at a greater risk of glaucoma. 

Regular eye exams are a crucial part of looking after your health. Because most cases of glaucoma develop gradually and do not initially have any symptoms, eye exams are especially important in detecting it. The effects of glaucoma are permanent and it cannot be cured, so treatment is aimed at reducing or stopping its progression. This means early diagnosis is vital to treating glaucoma effectively.  

For adults, it is recommended to have an eye exam at least once every two years. However, if you are at a greater risk of eye conditions like glaucoma your optometrist may recommend more regular checkups to monitor your eye health. Informing your optometrist of eye conditions in your family history and providing them with information about your health and lifestyle, will allow them to assess your risk of developing glaucoma. Understanding this can help you take the necessary steps to reduce your risk of developing the condition.  

References 

American Academy of Ophthalmology. (2021). Lifestyle Habits and Glaucoma. In EyeWiki. https://eyewiki.aao.org/Lifestyle_Habits_and_Glaucoma#:~:text=Diets%20high%20in%20fruits%20such,cranberries%20offer%20the%20most%20neuroprotection. 

Tham, Y. C., Li, X., Wong, T. Y., Quigley, H. A., Aung, T., & Cheng, C. Y. (2014). Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology, 121(11). 2081-2090.