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Vitreous Humor of the Eye: What It Is, Where It Is and What It Does
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Vitreous body (also vitreous humor, UK vitreous humour, or simply "the vitreous"; noun): the vitreous body is the clear, jelly-like gel that fills the large space between the lens and the retina at the back of the eye. It makes up about four-fifths of the eye's volume, holds the eyeball in its round shape and lets light pass through to the retina. It is about 98–99% water, and as we age it slowly shrinks and liquefies, which is why most people eventually notice floaters.
Vitreous humor of the eye: key facts
- Where it is
- Behind the lens and in front of the retina, filling the vitreous chamber (vitreous cavity)
- Share of the eye
- About four-fifths (80%) of the eyeball's volume; roughly 4 mL in an adult
- What it is made of
- About 98–99% water, plus a fine network of type II collagen fibres, hyaluronic acid and salts
- Consistency
- A clear gel with no blood vessels, two to four times as viscous as water
- Is it replaced?
- No. Unlike the aqueous humor, the vitreous is not continuously renewed
- Main jobs
- Gives the eye its round shape and a clear path for light to the retina
- Common problems
- Floaters, posterior vitreous detachment, retinal tears and detachment, bleeding into the vitreous
- Specialist
- Retina specialist (ophthalmologist); at Laser Istanbul Clinic, Doç. Dr. Muhammet Derda Özer and Op. Dr. Aysan Bayram
Doç. Dr. means Associate Professor of Ophthalmology.
Where is the vitreous humor located? The vitreous chamber of the eye
The vitreous humor sits in the back of the eye, between the lens in front and the retina behind. This space is called the vitreous chamber (or vitreous cavity), and it is by far the largest compartment of the eye. From front to back, light entering the eye passes through the cornea, the aqueous humor, the pupil and the lens, then crosses the vitreous gel before landing on the retina.
The vitreous is not simply floating loose. It is attached to its surroundings at a few key places:
- The vitreous base, a band of firm attachment at the front edge of the retina (the ora serrata), which is the strongest hold
- The optic disc, where the optic nerve leaves the eye
- The macula, the centre of the retina responsible for sharp central vision
- Retinal blood vessels and the back of the lens capsule
These attachments matter later in life, because they are where the vitreous can pull on the retina. For the retina itself, see our glossary entry Glossary: Retina →, and for the central part of the retina, Glossary: Macula and fovea →.
What is the vitreous humor made of? Vitreous humor composition
The vitreous humor is almost entirely water. According to EyeWiki (American Academy of Ophthalmology), the vitreous body is a transparent gel that is about 99% water, held together by extremely delicate type II collagen fibres, hyaluronic acid and electrolytes. Other sources give the water content as 98–99%.
| Component | Role |
|---|---|
| Water (about 98–99%) | Makes the vitreous clear and gives it its volume |
| Type II collagen fibres | A very fine mesh that gives the gel its structure |
| Hyaluronic acid | A long-chain molecule that holds water in the mesh, so the gel stays gel rather than runny |
| Salts (electrolytes), sugars and a few proteins | Small amounts dissolved in the water |
| Hyalocytes | Sparse cells at the edge of the vitreous, thought to make collagen and hyaluronic acid and to clear debris |
There are no blood vessels inside the vitreous. This is one reason it is so clear. It is also one reason it cannot repair or renew itself the way a tissue with its own blood supply can.
What produces the vitreous humor? Vitreous humor production
The vitreous forms before birth from embryonic tissue (mesenchyme) and is not continuously made and replaced during life. This is the key difference from the aqueous humor, which the ciliary body produces all the time. The cells at the periphery of the vitreous (the hyalocytes) are believed to make its collagen and hyaluronic acid, but the gel itself is not turned over like a fluid.
Two practical consequences follow:
- The vitreous slowly changes with age. The gel is present at birth, but pockets of liquid appear only from about age 4–5, and over the years the gel shrinks while the liquid portion grows.
- Lost vitreous is not regrown. If a surgeon removes the vitreous (vitrectomy), the space is filled with a replacement and then, in time, with the eye's own aqueous fluid, not with new vitreous gel. According to the American Academy of Ophthalmology, the eye naturally replaces a saline or gas bubble with aqueous humor during healing.
Small remnants of the eye's development are sometimes visible on examination, such as Mittendorf's dot and Bergmeister's papilla, which mark where a temporary embryonic blood vessel (the hyaloid artery) once ran through the vitreous. They are usually harmless.
What does the vitreous humor do? Vitreous humor function
The vitreous humor has two main functions, both structural.
1. It holds the eye's shape. The gel is substantial enough to fill the eye and give it its spherical form, keeping the retina smoothly in place against the back wall of the eye.
2. It lets light through. Because it is clear and free of blood vessels, light passes through the vitreous chamber to the retina without being scattered.
The vitreous is not what focuses light: that job belongs to the cornea and the lens. Nor does it regulate eye pressure; that is the aqueous humor's role. The eye can keep working after a vitrectomy, which is why surgeons are willing to remove the vitreous to reach and repair the retina.
Vitreous humor vs aqueous humor: location, production and function
The eye has two different fluids, and people often mix them up. The aqueous humor is a watery fluid in the front of the eye; the vitreous humor is a gel in the back.
| Aqueous humor | Vitreous humor | |
|---|---|---|
| Location | The front of the eye: the posterior chamber behind the iris and the anterior chamber behind the cornea | The vitreous chamber: the large space behind the lens, in front of the retina |
| Form | Thin, watery fluid (about 98% water) | Clear gel (98–99% water plus collagen and hyaluronic acid) |
| Share of the eye | A small volume | About four-fifths of the eye |
| Production | Made continuously by the ciliary body (its non-pigmented epithelium) | Formed before birth; not continuously produced |
| Renewal | Constantly drained and replaced | Not replaced |
| Function | Nourishes the cornea and lens, and keeps eye pressure stable | Holds the eye's shape and lets light through to the retina |
| Typical problems | Poor drainage raises eye pressure: glaucoma | Floaters, vitreous detachment, retinal tears and detachment, bleeding |
Aqueous humor and vitreous humor function together, not in competition. The aqueous humor circulates: it flows from the posterior chamber through the pupil into the anterior chamber and drains out through the trabecular meshwork at the angle of the eye. Abnormal drainage raises pressure inside the eye, which is how glaucoma damages the optic nerve. The vitreous, by contrast, stays put.
Vitreous body vs vitreous humor: is there a difference?
No. "Vitreous body", "vitreous humor" (US) / "vitreous humour" (UK) and "the vitreous" all describe the same gel. "Vitreous body" is the term anatomists prefer because it names a structure; "humor" is the older word for a bodily fluid, although the vitreous is a gel, not a free-flowing liquid. You may also see "vitreous cavity" or "vitreous chamber": that is the space the gel occupies.
How the vitreous changes with age: liquefaction and vitreous detachment
With age the vitreous gradually becomes less solid and more liquid. The collagen network collapses into strands and clumps, and pockets of liquid form in the gel. This is called vitreous liquefaction (syneresis), and it is a normal part of ageing. Floaters are more likely if you are short-sighted, have had cataract surgery or have had inflammation inside the eye.
The next step is posterior vitreous detachment (PVD). As the gel shrinks and liquefies, it separates from the retina at the back of the eye. According to the American Academy of Ophthalmology, PVD is a normal ageing process that occurs in most people by about age 70. EyeWiki describes it as typically developing in the sixth or seventh decade of life and affecting most eyes by 80.
Most PVDs cause nothing worse than a few floaters. The risk is in how the separation happens. If the vitreous is firmly stuck to the retina and pulls on it as it peels away, it can cause flashes of light and, in a minority of cases, tear the retina. A large study of 8,305 patients with symptomatic PVD, cited by EyeWiki, found a retinal tear in 5.4% and a rhegmatogenous retinal detachment in 4.0%. This is why new flashes and floaters should always be examined.
Problems of the vitreous humor: symptoms and conditions
| Condition | What happens | Typical symptoms |
|---|---|---|
| Floaters | Clumps and strands in the ageing vitreous cast shadows on the retina | Specks, dots, circles, lines or cobwebs that drift when you move your eyes, most visible against a plain background such as a blue sky |
| Flashes (photopsia) | The vitreous tugs on the retina, which the brain reads as light | Flashing lights or lightning-like streaks, usually in the side vision |
| Posterior vitreous detachment | The gel separates from the retina | Often new floaters and sometimes flashes; many people have no symptoms |
| Retinal tear or detachment | Traction from the vitreous tears the retina, and fluid can then lift it off the wall of the eye | New shower of floaters, flashes, a dark shadow or curtain in the side vision, blurred vision: an emergency |
| Vitreous hemorrhage | Blood leaks into the vitreous, for example from diabetic eye disease or a retinal tear | Sudden floaters, haze or a red-tinged blur |
| Macular hole or vitreomacular traction | The vitreous stays stuck to the macula and pulls on it, which can stretch the macula and cause a hole | Blurred, wavy or distorted central vision, sometimes a dark spot in the centre |
| Infection (endophthalmitis) | Severe infection inside the eye, which may involve the vitreous | Pain, redness, rapidly falling vision: an emergency |
Floaters and flashes are very common and usually harmless. The difficulty is that the same symptoms can also be the first sign of a retinal tear, and only an eye examination with dilated pupils can tell the difference.
How is the vitreous examined?
Because the vitreous is clear, it is examined indirectly. After dilating your pupil with drops, your ophthalmologist will look through the vitreous at the retina and check the vitreous itself.
- Slit-lamp examination with a dilated pupil. A microscope with a bright thin beam shows the vitreous gel, any floaters, pigment or blood in it, and whether the gel has separated from the retina.
- Examination of the peripheral retina. The doctor looks at the very edge of the retina with a special lens or a head-mounted light, where tears and thin areas usually start.
- Optical coherence tomography (OCT). A scan that gives a cross-section image of the retina and macula, and can show whether the vitreous is still pulling on the macula.
- Ultrasound (B-scan). If blood or other cloudiness blocks the view of the retina, an ultrasound scan can show whether the retina has detached.
Treatment: what can be done about vitreous problems
| Problem | Usual approach |
|---|---|
| Floaters and uncomplicated PVD | Usually nothing. Most floaters fade or become less noticeable over time, and the American Academy of Ophthalmology notes that removing severe floaters surgically carries risks and is seldom necessary or recommended |
| Retinal tear | Sealed with laser or cryopexy (freezing) to stop it becoming a detachment |
| Retinal detachment | Surgery: vitrectomy, scleral buckling, or pneumatic retinopexy (a gas bubble), chosen by the surgeon according to the type of detachment (NHS) |
| Vitreous hemorrhage | Examined to find the cause; blood sometimes clears on its own, and vitrectomy may be used for persistent bleeding or when the retina needs repair |
| Macular hole | Vitrectomy followed by a gas bubble that holds the hole closed while it heals |
What is a vitrectomy?
A vitrectomy is a type of eye surgery in which the surgeon removes some or all of the vitreous gel through tiny incisions in the white of the eye (the sclera). According to the American Academy of Ophthalmology, it is used for retinal detachment, macular hole and macular pucker, bleeding and scar tissue in diabetic retinopathy, severe eye infections, severe injuries and some complications of cataract surgery. The vitreous is replaced with saline, a gas or air bubble, or silicone oil (which needs a second operation to remove). Risks include infection, bleeding, retinal damage, raised eye pressure and cataract, especially in people over 50. After a gas bubble, flying, mountain travel and scuba diving are not allowed until the bubble has gone.
Treatment with us: retina care, including vitrectomy and retinal detachment repair, is led by Doç. Dr. Muhammet Derda Özer and Op. Dr. Aysan Bayram. Your surgeon reviews your scans and examination findings before recommending anything.
When to see a doctor about your vitreous
Seek same-day care from an eye doctor or eye emergency service if you notice:
- a sudden shower of new floaters
- frequent flashes of light
- a dark shadow or grey curtain moving across part of your vision
- a sudden drop in vision
- pain and redness with falling vision, especially after eye surgery or an injury
The American Academy of Ophthalmology advises seeing your ophthalmologist as soon as possible if you notice a lot of floaters or flashes suddenly, or a decrease in vision. The NHS says a detached retina needs to be treated quickly to stop it permanently affecting sight, and advises calling NHS 111 if symptoms start suddenly.
Book a routine appointment if you have:
- long-standing floaters that have not changed
- floaters that bother you in daily life
- short-sightedness, a family history of retinal detachment, or previous eye surgery, and you want a retina check
If you are abroad and have symptoms like these, do not wait to travel: get examined locally first. If you already have a diagnosis and want a second opinion on retina surgery, you can send us your reports and scans.
Frequently asked questions
The vitreous humor is the clear, jelly-like gel that fills the space between the lens and the retina. It makes up about four-fifths of the eye's volume and is about 98–99% water. It gives the eye its round shape and lets light travel to the retina.
It sits in the vitreous chamber at the back of the eye, behind the lens and in front of the retina. The aqueous humor, by comparison, fills the front of the eye.
Mostly water (98–99%), with a fine network of type II collagen fibres, hyaluronic acid, salts and a few cells (hyalocytes). There are no blood vessels in it.
It develops before birth from embryonic tissue and is not continuously produced afterwards. Cells at its edge, called hyalocytes, are thought to make its collagen and hyaluronic acid. Unlike the aqueous humor, which the ciliary body makes constantly, the vitreous is not renewed.
It maintains the eye's spherical shape and provides a clear path for light to reach the retina. It does not focus light itself.
The aqueous humor is a watery fluid in the front of the eye that is made continuously by the ciliary body and drains away, maintaining eye pressure and nourishing the cornea and lens. The vitreous humor is a gel in the back of the eye that is not replaced. Aqueous problems cause glaucoma; vitreous problems cause floaters and retinal tears.
Yes. Vitreous body, vitreous humor and vitreous are different names for the same gel.
Floaters are shadows from gel clumps inside the ageing vitreous. They are more likely if you are short-sighted, have had cataract surgery or have had eye inflammation. Most are harmless, but a sudden increase, flashes or a shadow in your side vision should be checked urgently.
It can be removed in a vitrectomy and replaced temporarily with saline, gas or silicone oil. The eye does not regrow the vitreous; the space gradually fills with the eye's own fluid, and the eye continues to function.
Sources for the facts on this page
- American Academy of Ophthalmology. Vitreous. https://www.aao.org/eye-health/anatomy/vitreous
- American Academy of Ophthalmology. Parts of the eye (eye anatomy). https://www.aao.org/eye-health/anatomy/parts-of-eye
- American Academy of Ophthalmology. What are floaters and flashes? https://www.aao.org/eye-health/diseases/what-are-floaters-flashes
- American Academy of Ophthalmology. What is posterior vitreous detachment? https://www.aao.org/eye-health/diseases/what-is-posterior-vitreous-detachment
- American Academy of Ophthalmology. What is a macular hole? https://www.aao.org/eye-health/diseases/what-is-macular-hole
- American Academy of Ophthalmology. What is vitrectomy? https://www.aao.org/eye-health/treatments/what-is-vitrectomy
- EyeWiki (AAO). Posterior Vitreous Detachment. https://eyewiki.aao.org/Posterior_Vitreous_Detachment
- EyeWiki (AAO). Basic Histology of the Eye and Accessory Structures. https://eyewiki.org/Basic_Histology_of_the_Eye_and_Accessory_Structures
- NHS. Retinal detachment. https://www.nhs.uk/conditions/retinal-detachment/
- Wikipedia. Vitreous body (volume of about 4 mL and four-fifths of the eye, 98–99% water, viscosity, attachments, development, not replaced). https://en.wikipedia.org/wiki/Vitreous_body
- Wikipedia. Aqueous humour (production by the ciliary body, about 98% water, drainage pathway). https://en.wikipedia.org/wiki/Aqueous_humour
Seeing new floaters or flashes, or told you may need retina surgery?
Send us your scans or eye report. Our retina surgeons, Doç. Dr. Muhammet Derda Özer and Op. Dr. Aysan Bayram, will review them and tell you which treatments may suit your eyes, with no obligation. If your symptoms are sudden, see an eye doctor locally first.
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