What is Primary Open Angle Glaucoma?
Primary Open Angle Glaucoma (called “glaucoma” on this website) is an eye condition in which loss of vision results from optic nerve damage, most often due to increased pressure within the eye. It mainly occurs when the eye’s drainage canals become clogged over time and the correct amount of fluid can’t drain out of the eye. Loss of vision in glaucoma is usually gradual and affects peripheral (side) vision first. There can be significant loss of vision before there is an awareness of any problem.
In Australia, 300,000 people have glaucoma; about 1 in 200 people have glaucoma by age 40, increasing to 1 in 8 by age 80. Around 50% of glaucoma is undiagnosed1.
Vision lost to glaucoma is unfortunately irreversible once it has occurred. However, once diagnosed, glaucoma can usually be managed successfully with eye drops, laser therapy, or surgery.
Glaucoma has a strong genetic component. Family members of people with glaucoma have a higher risk of the condition.
What are the main risk factors for glaucoma?
The risk that a person will develop glaucoma in future, or that already-diagnosed glaucoma will get worse, depends on a wide range of factors2. These include:
- Risk factors such as an age over 50, a family history of glaucoma, or being of African descent
- Clinical features such as high eye pressure, certain types of vision loss, or signs of optic nerve damage
- Variations in genes that influence the risk of glaucoma
How can genetics be used to assess glaucoma risk?
Humans share the same genetic code apart from some differences, called genetic variants, that make each of us unique. Some of these variants are known to increase the risk of developing glaucoma, while others reduce the risk. It is possible to combine the risks from hundreds or thousands of these genetic variants to estimate a person’s genetic risk of developing glaucoma in future or, if they already have glaucoma, the risk their glaucoma might get worse, relative to others in the community.
How does genetic risk relate to family history?
Blood relatives (e.g. parents, brothers/sisters, adult children) share parts of their genetic code and will have some of the same genetic variants. Thus, for conditions with a strong genetic contribution, such as glaucoma, a healthcare practitioner will take account of a person’s family history when assessing their risk.
However, a family history is not the same as a person’s individual genetic risk. It is possible to have a high genetic risk of glaucoma without a family history of the condition. It is also possible to have a family history of glaucoma and have a lower individual genetic risk. This is because a family history does not mean a person has personally inherited the genetic variants that increase the risk of glaucoma.
Analysing a person’s unique genetic code may provide a health practitioner additional information about an individual’s risk of developing glaucoma relative to others with a family history of glaucoma.
How is genetic testing performed?
Genetic testing may be performed by collecting a saliva sample, extracting the DNA inside, and then analysing genetic results.
SightScoreTM is a clinical genetic testing service provided by Seonix Bio, based on an accredited genetic risk score. It estimates a person’s genetic risk of developing glaucoma in future or, if they already have glaucoma, the risk their glaucoma might get worse, relative to others in the community. SightScore must be ordered be an appropriate health practitioner, most commonly an optometrist or ophthalmologist.
How can glaucoma risk information be used by a healthcare practitioner?
Together with other clinical features, examination and medical history, a healthcare practitioner may use glaucoma genetic risk information to consider how to manage:
- The age for a person’s first glaucoma check,
- How often a person should be checked for glaucoma,
- Whether a person is best monitored in optometry or ophthalmology,
- How best to care for a person with glaucoma, including some treatment decisions; and
- Whether blood relatives (parents, brothers/sisters, adult children) should be checked for glaucoma.
It may also be useful for individuals to better understand their risk so they can be proactive in their healthcare.
What can be done about glaucoma risk?
The most important thing is to follow the advice of a healthcare practitioner and particularly, to attend regular eye health check-ups. Once diagnosed, glaucoma can usually be managed successfully with eye drops, laser therapy, or surgery. A key goal of care is to detect glaucoma as early as possible.
A healthy lifestyle, including avoidance of smoking, moderate exercise and a balanced diet, is also recommended3.
1. Glaucoma Australia. https://glaucoma.org.au/
2. Grzybowski A, et al., 2020. Primary Open Angle Glaucoma and Vascular Risk Factors: A Review of Population Based Studies from 1990 to 2019. J Clin Med. 9(3):761.
3. Pasquale LR, Kang JH., 2009. Lifestyle, nutrition, and glaucoma. J Glaucoma. 18(6):423-8.