by Subhuti Dharmananda, Ph.D., Director, Institute for Traditional Medicine, Portland, Oregon

The nature of floaters can be understood in terms of the fluid in which they occur, namely the vitreous. This is a gel matrix filling the vitreous cavity, making up about 2/3 the volume of the eye. In front of it is the lens structure, behind it is the retinal structure. The vitreous is a transparent gel, about 98% water, but it is 2-4 times more viscous than water, mainly due to the content of sodium hyaluronate (the salt of hyaluronic acid, a component of many fluid structures in the body). The hyaluronic acid molecules are large coils that hold water; in the vitreous they are entrapped in a matrix of collagen fibers (type II, the main fiber making up cartilage). Most of the collagen is at the surface region of the vitreous, where it comes in contact with the rest of the eye, giving it a somewhat more solid surface. There is less collagen in the central region, which is a more liquid portion, comprised of about 99% water. Collagen fibrils attach the vitreous gel to points around its margin, particularly to the retinal and lens structures.

The vitreous mainly functions as a transparent fill for the eyeball. The fluid maintains the shape of the eye, acts as a shock absorber, allows transmission of light to the retina, and helps maintain the contact between the retina and the back wall of the eye by applying a mild pressure. It contains no blood vessels and is essentially cell free. A few cells may be present near the retina, including hyalocytes that appear to be responsible for producing hyaluronic acid; these are similar to immune cells called macrophages. Aside from hyalocytes, there are other sources of the vitreous components among the various types of cells of the eye structure, though it is not yet established which ones play a key role.

The original three-dimensional net-like structure of collagen fibers begins to deteriorate once body growth has halted at adolescence. This deterioration is slow and involves having some strands of collagen clump up, and some of the original compartments of gel merge into larger compartments. At this point, "floaters" may begin to appear. Many people believe that these floaters are materials released into the eye, when, in fact, they are shadows on the retina from light encountering the irregularities in the gel matrix. Such irregularities are mainly caused by coalesced collagen filaments, forming fibrils. The floaters are especially visible while looking at a plain, well-lit background.

Diagram of the eye, with floaters

It is not until middle age, around age 40, that there are significant changes in the vitreous that generate floaters. The vitreous begins to slowly dry out, and the collagen becomes more clumped, leaving the vitreous almost entirely a free flowing fluid with some intervening gel lumps. These produce the floaters that are most frequently reported. They tend to "float" more easily because of the breakdown of the gel matrix. Nothing needs to enter the vitreous to make these floaters and nothing is present to break down the floaters, so they remain for many months. They may eventually degrade or settle out, or they may persist.

With further aging, the vitreous will dry, thicken, and shrink to an extent that it starts to pull away from the retina (the condition is called posterior vitreous detachment). This process may be the result of a sudden drying of the fluid, rather than the gradual drying that is normally expected. When a sudden vitreous shrinkage occurs, there can be a substantial appearance of floaters over a short period.

While vitreous detachment through a gradual process is common by age 70, it occurs more often and sometimes earlier in people who are nearsighted, have undergone cataract surgery or laser eye surgery, or who have an inflammatory disease of the inner portion of the eye, such as retinitis. When the vitreous gel pulls away from the retina, nothing may happen (vision remains basically the same), but this pulling can cause some retinal tears. Tearing of the retina may allow some blood cells to flow into the vitreous cavity, which accounts for some of the new floaters; other floaters may appear as a result of contraction of the fibers that had been attaching the vitreous to the retina.

When a retinal tear occurs, some of the vitreous fluid can penetrate into the torn areas and lift away the rest of the retina, which is extremely thin, leading to partial or full detachment. During retinal tearing or detachment, flashes of light (like flurries of fireflies) are detected by the patient, and the vision may be blurred, particularly in certain portions of the visual field. The torn retina should be examined carefully, as it may require treatment, such as laser photocoagulation, cryopexy (freezing), or surgery, to avoid complete retinal detachment or to treat a detached retina.

The condition of the vitreous fluid and the nature of floaters are observed by dilating the eye (applying eye drops to do so), and then examining the region through the pupil. There are no medical treatments for floaters. Some floaters, particularly those that occur as a young adult, will eventually disappear as the gel matrix changes. Other floaters, particularly those that occur in later years, may disappear as they settle out of the fluid. In persons suffering from severe disorders of the vitreous, which occurs in some cases of diabetes or where injuries have allowed blood into the vitreous, a vitrectomy may be performed; the vitreous is removed and placed with an artificial substitute liquid called hyaluronate.


Little is known about what causes the changes in the vitreous with age, and what can speed up or slow down the process. It is relatively easy to speculate on some potential causes. It is known that excessive exposure to sunlight can cause damage to the eyes and skin, and is a contributor to cataract formation and drying, wrinkling skin. There is no reason to think that these types of effects could not occur in the vitreous to some extent, perhaps contributing to the clumping of the collagen fibers and the drying of the fluid. Hence, a rational protective effort would be to utilize good quality sunglasses and, in cases where there is considerable exposure to sun, to utilize shading (such as a visor or hat). Similarly, one should be careful about exposure to bright lights from copy machines, lasers, and other indoor sources. The drying of fluid within the eyes may be accelerated by poor circulation in the retina (capillary bed circulation) and by general lack of hydration. Blood circulation can be worsened by high blood sugar, high blood fat, and high oxidative levels in the blood, while it can be improved by maintaining healthy blood conditions and having a diet rich in flavonoids and antioxidants; hydration is improved by drinking plenty of water, juice, tea, or other healthy beverages. Thus, protecting the eyes and maintaining good circulation and hydration are potential preventive measures for floaters, retinal tearing, and retinal detachment.


In the Yinhai Jingwei (Essential Subtleties on the Silver Sea), a text on ophthalmology from the time of the Ming Dynasty (1), there is a discussion of floaters, described as "black blurred specks in the eyes resembling fly wings." The pathology is said to be related to the "water of the kidney" refers to the kidney yin, as distinguished from the "fire of the kidney," which corresponds to the kidney yang or mingmen fire:

[Floaters] are a sign of weakness of the water of the kidney. The kidney is the mother of the liver. If the water of the kidney can not nourish the wood of the liver, the liver will display deficiency heat. The gallbladder lies beside the liver. If the wood of the liver is withered and parched, the qi of the gallbladder will be insufficient. As a result, whenever one starts or halts a movement of the head, black specks resembling fly wings float in the spirit water of the eyes. To regulate this condition, one must first employ Zhuling San (Polyporus Powder) to return the evil fire in one's liver and in the kidney to normalcy. Next, one employs Heishen Tang (Scrophularia Decoction) to cool the liver. Then the conduit of the gallbladder will no longer be invaded by evil heat. Afterward, one employs Bushen Wan (Supplement the Kidney Pills). Then the black specks will disappear by themselves.

The formulas mentioned for this condition are as follows:

Zhuling San
(Polyporus Powder)
Polyporus 30 g
Akebia 30 g
Rhubarb 30 g
Gardenia 30 g
Cibotium 30 g
Talc 30 g
Polygonum 30 g
Plantago seed 15 g
Red atractylodes 15 g
Instructions: grind the ingredients to powder; one dose is 9 grams, to be consumed with salty water.

Actions: This formula clears damp-heat of the liver/gallbladder and the kidney/bladder; it is comprised mainly of bitter herbs of cold nature. Most of the herbs are classified as diuretic in modern terms; rhubarb and gardenia purge the gallbladder.

Heishen Tang
(Scrophularia Decoction)
Scrophularia Scute
Raw rehmannia Chrysanthemum
Red peony Celosia
Instructions: to grind the ingredients in equal parts to powder. Each dose is 12 grams, with the powder boiled in water for a brief time and the resulting decoction consumed.

Actions: These herbs clear heat from the blood and dispel wind-heat from the eyes.

Bushen Wan
(Supplement Kidney Pills)
Ginseng Acorus
Hoelen Lycium
Peony Cuscuta
Alisma Cistanche
Instructions: grind equal amounts of these herbs to powder, mix with honey to form pills. The quantity of the herbs to be used for each dose is unclear.

Actions: This formula nourishes the kidney and moistens the essence.

The same text includes a description of retinal detachment, as "the eyes turn dull and develop specks:"

Retinal detachment is caused by depletion in the kidney. Even though the eyes belong to the orifices [that is, the eyes are the orifices associated with the liver], they are tied to the kidneys as their ruler. When the kidney is depleted, the eyesight will become dim. Greed, licentiousness, overindulgence in pleasures, and an unrestrained passion for wine and women weaken and exhaust the kidney. Or, when a person's original qi and essence are incomplete, or when essential spirits have become insufficient, all this causes the pupil and the spirit water to lose their clarity and the eyes to be without strength. As a result, the eyes develop specks and the patient is unable to watch anything for an extended time. To regulate this condition, one must employ Bushen Guijing Wan (pills to nourish the kidney and return the essence). They cause the yin water to be sufficient again, and to return everywhere.

Bushen Guijing Wan (Pills to nourish the kidney and return the essence)


The instructions are to grind the herbs to powder, combine with honey, and form pills, or boil the powder in water to make a decoction. The total amount of herbs to be consumed for each dose is unclear. This formula includes several herbs for nourishing the eyes and dispelling wind-heat.

According to this text, the fluid in the vitreous cavity is viewed as an integral part of the kidney water, or yin essence. When the kidney's yin essence is depleted, not only does the eye fluid become drier, but the wood of the liver/gallbladder system dries out. This causes a turbid essence to go upward from the gallbladder, and a weak fire to arise from the liver and kidneys, which combines with invading wind and distorts the fluid contents of the eye. The gallbladder channel starts at the corner of the eye (tongziliao; GB-1, a point indicated for redness and pain of the eyes, failing of vision, and excess tearing). The remedy is to lower the fire, clear it, and then replenish the fluids.

Just as modern medicine recognizes the vitreous fluid as an original fluid of the developing eye, the Chinese doctrine views it as part of the "original water" associated with the kidney, but located in the upper body (referred to as heavenly original water; tian yizhi shui). It degrades by the weakening of the kidney and the invasion of pathogenic influences, such as internal heat from the liver/gallbladder and external wind-heat.

A formula devised after the Yinhai Jingwei was written, Qi Ju Dihuang Wan (Lycium, Chrysanthemum, and Rehmannia Formula), is an example of an eye nourishing prescription used to treat this basic condition. Similarly, the eye-brightening formula, Mingmu Dihuang Wan (Eye-brightening Rehmannia Formula) is aimed at alleviating the dry deficiency of kidney and liver. Yet another formula, Yiqi Congming Tang, is designed to clear the deficiency heat and dispel wind-heat, while benefiting the kidney water indirectly, by nourishing the spleen. It is indicated for deteriorating vision with aging.

In the English-Chinese Encyclopedia of Practical Traditional Chinese Medicine (2), there is a short section on diseases of the vitreous. The clinical manifestations are said to range from mild cases with black shadows floating up and down like flying flies (but no other change in vision) to severe cases, where the eyes seem to be covered by a membrane. There are three categories of causation listed:


Floaters are rarely caused by release of materials into the eye, and are not a sign of blood deficiency, as is often relayed to Western acupuncturists. Rather, they are a result of natural processes that may be exacerbated or accelerated by overexposure to sunlight, poor circulation in the retina, and lack of hydration, along with deficiency of yin essence and associated flaring of deficiency heat or accumulation of damp-heat. Although there is no proof that the formulas described in the Chinese texts can eliminate floaters and prevent retinal detachment, the use of the herbs and formulas described here is consistent with the basic tenets of the Chinese medical system. In general, one wishes to clear deficiency heat, gently dry damp-heat, and nourish the fluids, particularly the kidney yin, to assure the moistness of the vitreous.


  1. Kovacs J and Unschuld PU, Essential Subtleties on the Silver Sea, 1998 University of California Press, Berkeley, CA.
  2. Xu Xiangcai (chief editor), The English-Chinese Encyclopedia of Practical Traditional Chinese Medicine, vol. 17: Ophthalmology, 1994 Higher Education Press, Beijing.

    December 2002