Skip to main content
Clear
  • Find a store
  • Menu
Specsavers logo
  • My account Log in
    • My favourites
    • Express re-order
    • Orders
    • My details
    • Payment methods
    • Log out
  • Re-order contact lenses
    • Glasses
        • Glasses
        • Women
        • Men
        • Unisex
        • Kids
        • Harry Potter™ collection
        • adidas Sport collection
        • adidas Originals collection
        • Glasses
        • Sunglasses
        • Designer glasses
        • Designer brands
        • Our glasses collections
        • Find your glasses
        • Do I Need Glasses?
        • Guide to lenses
        • Buyer's guide
        • Online ordering
        • Order replacement glasses
        • Lens extras and treatments
        • Do blue light glasses work?
        • #loveglasses blog
        • Accessories
    • Contact lenses
        • Contact lenses
        • Product type
        • View all
        • Daily
        • Monthly
        • Information
        • Direct Debit scheme
        • easycare log in
        • Buying contact lenses
        • Contact lens guide
        • Express re-order
    • Eye health
        • Eye health
        • Online Consultation Service
        • Book an eye test
        • OCT Scan
        • Eyecare at work
        • Care Hub - (COVID-19 Information)
        • All about PRSI and Medical Cards
        • Eye conditions & symptoms
        • Children's eyecare
        • Do I need an eye test?
        • How to obtain your prescription
        • FAQs
    • Hearing
        • Hearing
        • Hearing tests
        • Hearing
        • Book a free hearing test
        • Earwax removal
        • Free online hearing test
        • Product
        • Hearing aid prices
        • Hearing aids
        • PRSI hearing aid benefits
        • Great offers
        • Information
        • All about PRSI and Medical Cards
        • What happens in a hearing test
        • All about earwax
        • Understanding hearing loss
    • Offers
        • Offers
        • Glasses
        • 2 for 1 glasses & sunglasses
        • 2 for 1 designer glasses
        • 2 for 1 glasses from €89
        • 20% off glasses for over-60s
        • Free eye test & glasses with PRSI
        • Complete glasses from €19
        • Great offers for kids
        • 25% off glasses for students
        • Lenses
        • 2 for 1 varifocal glasses
        • Free UltraClear SuperClean
        • Free reactions
        • Free varifocals
        • Polarising lenses only €89
        • Contact lenses
        • First month's free contact lenses
        • Free glasses with contact lenses
        • Free easyvision contact lenses with glasses from €89
        • Hearing
        • Invisible hearing aids from €600
        • Free hearing tests
        • Hearing aid prices
        • Hearing product bundles
    • Book appointment
    • Find a store
    • Re-order contact lenses
    • Log in
    • My account
    • My favourites
    • Log out
  • Book appointment Book appointment
Age and Gender
  • Women
  • Men
  • Unisex
  • Kids
  • Harry Potter™ collection
Type
  • Glasses
  • Sunglasses
  • Designer glasses
  • Designer brands
  • Our glasses collections
  • adidas Originals collection
  • adidas Sport collection
Guides
  • Find your glasses
  • Buyer's guide
  • Online ordering
  • Guide to lenses
  • Lens extras and treatments
  • Do blue light glasses work?
  • Order replacement glasses
  • Accessories
  • #loveglasses blog
  • Do I Need Glasses?
Vivienne Westwood collection
Glasses and sunglasses
2 for 1 from €199
Browse the collection
Product type
  • Daily
  • Monthly
  • Multifocal
  • Toric
  • View all
Brand
  • easyvision
  • Acuvue
  • Focus
  • View all
Information
  • Direct Debit scheme
  • easycare log in
  • Buying contact lenses
  • Contact lens guide
  • FAQs
  • Express Re-order
Specsavers express re-order
Buy Online
Buy your contact lenses online and get free delivery
Buy Now
Services
  • Online Consultation Service
  • Book an eye test
  • Eyecare at work
  • OCT Scan
Information
  • Care Hub - (COVID-19 Information)
  • Your store visit explained
  • Your prescription explained
  • Eye conditions & symptoms
  • PRSI/Medical card funded eye tests
  • All about PRSI and Medical Cards
  • Children's eyecare
Help
  • Do I need an eye test?
  • FAQs
  • How to obtain your prescription
Book appointment
Book appointment
Pop in for an eye test to give your eyes all the care they deserve
Book now
Services
  • Book a free hearing test
  • Hearing tests
  • Earwax removal
  • Hearing aid aftercare
  • Free online hearing test
  • Hearing
Product
  • Hearing aid prices
  • Hearing aids
  • Hearing aid brands
  • PRSI hearing aid benefits
  • Great offers
  • All about hearing protection
Information
  • What happens in a hearing test
  • All about earwax
  • All about PRSI and Medical Cards
  • Understanding hearing loss
  • Download an information sheet
Book appointment
Do you qualify for PRSI benefits or have a medical card?
With PRSI, you could be eligible for free hearing aids
Book now
Glasses
  • 2 for 1 glasses & sunglasses
  • 2 for 1 designer glasses
  • 2 for 1 glasses from €89
  • 20% off glasses for over-60s
  • Free eye test & glasses with PRSI
  • Complete glasses from €19
  • Great offers for kids
  • 25% off glasses for students
Lenses
  • 2 for 1 varifocal glasses
  • Free UltraClear SuperClean
  • Free reactions
  • Free varifocals
  • Polarising lenses only €89
Contact lenses
  • First month's free contact lenses
  • Free glasses with contact lenses
  • Free easyvision contact lenses with glasses from €89
Hearing
  • Invisible hearing aids from €600
  • Free hearing tests
  • Hearing aid prices
  • Hearing product bundles
  1. Home

Understanding glaucoma: what is the aqueous humour?

Glaucoma is linked to a build-up of pressure in the eye caused by an imbalance in the production and drainage of a fluid called the aqueous humour.

The increased pressure can damage the optic nerve, which can create blind spots in the visual field (small areas of your vision where there is no image detection). If left untreated, glaucoma can lead to irreversible vision loss.1 But in order to understand the condition and how it can progress, it’s important to know what causes it, and the important role aqueous humour plays in this.

What is the function of aqueous humour?

Aqueous humour is a thin, watery fluid produced by the eye and, in a healthy eye, it’s in a constant cycle of production and drainage. The aqueous humour is 99.9% water and 0.1% nutrients such as glucose, proteins and vitamins. These nutrients nourish the cornea and lens and keep the eye healthy, as well a protect the cornea against the wind, pollen, dust, and pathogens.

This fluid fills the spaces between the cornea and iris (anterior chamber) and the iris and lens (posterior chamber), which gives the eye its round shape and controls intraocular pressure (IOP).2 It’s secreted by a structure called the ciliary body which is an extension of the iris (the coloured portion of the eye).

How does aqueous humour control IOP?

In a healthy eye, a certain amount of aqueous humour flows into the eye and the same amount drains out. This process keeps the IOP within ‘normal limits’.

However, variations in the production or outflow of aqueous humour can lead to significant changes in intraocular pressure. In most forms of glaucoma, vision loss occurs due to an increase in IOP caused by an imbalance in the production or outflow of the aqueous humour, and it’s this build-up of pressure which can cause permanent damage to the optic nerve.3

How is aqueous humour produced and drained?

Aqueous humour is actively secreted into the eye by the ciliary body (the ciliary body also controls the shape of the lens). This is the part of the eye that connects the cornea to the choroid (the vascular layer of the eye). Active secretion is the most important part of aqueous humour production and this is controlled by enzymes and proteins deep inside the ciliary body.4

The fluid leaves the eye through two principle routes: the trabecular meshwork (an area of tissue at the base of the cornea) and the uveoscleral pathway.

The trabecular meshwork is responsible for 75% of the resistance to aqueous humour outflow. If this site becomes blocked by a deposit of proteins or other substances, for instance, an imbalance is caused in the production and drainage cycle — leading to an increase in IOP.

The second pathway for aqueous humour drainage, the uveoscleral pathway, is relatively independent of IOP, but effective drainage via the uveoscleral pathway decreases with age.4 Age, potentially as a result, is also one of the key risk factors for glaucoma development.

How does aqueous humour help inform glaucoma treatment?

The role of the aqueous humour in the development of glaucoma is well known, but the type of glaucoma will usually depend on which part of the production or drainage system has been affected. Current treatments for glaucoma focus on lowering the IOP by increasing the outflow of aqueous humour or suppressing its production.

Eye drops are the most common form of glaucoma treatment and can be tailored to glaucoma type and need. For example, eye drops that contain carbonic anhydrase inhibitors (e.g. dorzolamide) and beta-blockers (e.g. timolol) decrease the production of aqueous humour by the ciliary body. Prostaglandins (e.g. latanoprost), on the other hand, increase the outflow of aqueous humour through the uveoscleral pathway and trabecular meshwork. While eye drops containing alpha-adrenergic agonists (e.g. brimonidine) perform both functions.

Surgical treatments for glaucoma can also be used to lower IOP by increasing aqueous humour drainage or reducing its formation.

Some laser treatments target the part of the ciliary body responsible for aqueous humour production to lower IOP. Other procedures such as trabeculectomy or laser trabeculoplasty modify the trabecular meshwork to decrease outflow resistance.

Glaucoma shunts are sometimes recommended for some patients to bypass the trabecular meshwork and improve drainage. Another option is canaloplasty — a procedure that opens up the uveoscleral pathway and increases aqueous humour outflow through existing pathways.4

If you have any concerns and queries regarding glaucoma treatment, please don’t hesitate to ask your optometrist. They will be able to advise you effectively, as well as explain more about the function of aqueous humour.

If you found this information about aqueous humour helpful, however, then do browse our dedicated glaucoma resources. There’s a wealth of expert-led content explaining the causes of glaucoma, glaucoma diagnosis and glaucoma treatment.

References

1. University of Washington. (no date). Eye Diseases – Glaucoma. [Online]. Available at: https://faculty.washington.edu/chudler/glaucoma.html [Accessed 6 August 2019].
2. Vision Eye Institute. (no date). The Aqueous Humour. [Online]. Available at: https://visioneyeinstitute.com.au/eyematters/aqueous-humour/ [Accessed 6 August 2019].
3. American Academy of Ophthalmology. (no date). Causes of Glaucoma. [Online]. Available at: https://www.aao.org/eye-health/diseases/glaucoma-causes [Accessed 6 August 2019].
4. Goel, M., Picciani, R. G., Lee, R. K., & Bhattacharya, S. K. (2010). Aqueous humor dynamics: a review. The open ophthalmology journal, 4, 52–59. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3032230/ [Accessed 6 August 2019].

Josie Forte
DOptom BSc(Hons) MCOptom

Josie is an optometrist registered with the UK General Optical Council and New Zealand Board of Optometrists and Dispensing Opticians. She graduated from Cardiff… Read more

Causes of glaucoma

Find out more

Diagnosis of glaucoma

Find out more

Meet our experts

Find out more

Glaucoma hub
 

Find out more

Book an appointment
  • Browse
    • Glasses
    • Sunglasses
    • Designer Glasses
    • Contact lenses
    • Hearing aids
    • Offers
    • Gift vouchers
  • Services
    • Eye test in store
    • Eyecare at work
    • OCT scans in store
    • Hearing test
    • Hearing test at home
  • COVID-19 Information
    • Glasses fogging up advice
    • Keeping you safe in store
    • Use of PPE in store
    • Your new in store experience
  • About Specsavers
    • About Specsavers
    • Contact us
    • Careers
    • Sustainability
    • Reports
    • Sitemap
    • Specsavers promise
  • © Specsavers 2023
  • Help
  • Legal Policies
  • International Sites
  • 22.12.2