Vitreous disorders and diseases of the vitreous body in the eye

The vitreous body (corpus vitreum) is an integral part of the eye in all vertebrates. It fills the entire posterior chamber of the eye and is responsible for maintaining the shape of the eyeball.

The Structure of the Eye @ bilderzwerg /AdobeStock

Inside the eye lies the vitreous body (corpus vitreum), which has a spherical and transparent structure. It is bounded by the lens at the front and the retina at the back. It is located in the posterior chamber of the eye.

The vitreous body consists of 98 percent water and has a gel-like consistency. It contains neither nerves nor blood vessels. Clinically, doctors can sometimes detect a vestigial remnant of the embryonic artery.

During the embryonic phase, this blood vessel transports all the substances necessary for the eye’s development into the eyeball. The hyaloid artery regresses only toward the end of embryonic development. It remains in the vitreous humor as the Cloquet canal for the rest of a person’s life.

After the eye refracts and focuses light rays on the cornea and lens according to the angle of incidence, they pass through the vitreous body. The light rays then strike the retina, which lies behind the vitreous body and contains photoreceptors.

These receptors convert the light stimuli into electrical signals. This initiates a highly complex signaling cascade that extends all the way to the central nervous system. The brain then interprets the signals as images.

An important prerequisite for the unimpeded passage of light rays to the retina is the transparency of the vitreous humor.

Various processes can lead to changes in the vitreous body.

These include, for example:

• Normal aging processes
• Degenerative changes associated with nearsightedness
• Inflammation
• Bleeding

To diagnose a condition, the pupil must be dilated with medication. This allows the ophthalmologist to examine the structures of the vitreous body, retina, and choroid using a loupe or a contact lens. Since driving is prohibited when the pupil is dilated, you should always visit the ophthalmologist without a car.

Annoying but simple vitreous opacities often do not require treatment, as these opacities settle within the vitreous humor. Those affected usually no longer notice them. They have no effect on vision.

Other causes, such as retinal tears, inflammation, or vitreous hemorrhages, require treatment. Surgical removal of the vitreous (vitrectomy) is necessary only in rare cases.

The majority of physiological and pathological changes in the vitreous are characterized by floaters.

“Floaters” in the Eyes

These opacities manifest as grayish-translucent, indistinct double outlines that drift slowly and move along with the gaze.

Colloquially, they are also called “mouches volantes” (floaters), which are actually only one type of vitreous opacity. The opacities are more clearly visible when looking at bright areas (a white wall, the sky). Visual acuity is not affected. Although almost all patients find them bothersome at first, they learn to live with them over time.

Vitreous opacities are generally harmless and occur in many people. They do not indicate any specific disease, which is why they do not require treatment. If patients find them too bothersome, laser treatment may help. Surgical removal of the vitreous is rarely necessary.

Before the procedure, the doctor should carefully weigh the risks and benefits together with the patient. If visual acuity decreases significantly, or if the situation is distressing for the patient, such a procedure may be appropriate.

As a general rule: Any concerns regarding vitreous opacities should be evaluated by a doctor. The doctor can rule out serious conditions and prescribe appropriate treatment.

Over the course of a person’s life, the vitreous humor detaches from the retina. Doctors refer to this process as vitreous detachment. It is caused by the progressive liquefaction of the vitreous humor, followed by its subsequent detachment from the retina. Vitreous detachment is an age-related process that affects everyone. Normally, no serious complications are expected.

As a result of the detachment, the posterior limiting membrane of the vitreous shifts in front of the retina. This causes opacities on this limiting membrane to become visible.

These opacities, along with those caused by the thickening of the central vitreous, are perceived by those affected as ring- or snake-shaped lines. For this reason, experts also refer to them as “floaters.” These floaters move along with eye movements.

Possible complications of vitreous detachment include:

• Severe retinal traction leading to retinal tears (formation of holes)
• Retinal detachment

This is an absolute medical emergency that doctors usually must treat within a few hours. If a detached retina is not surgically reattached, it will lead to blindness. 

Prompt treatment is crucial in cases of retinal detachment @ bilderzwerg /AdobeStock

Vitreous opacities accompanied by many black spots, as well as seeing flashes of light, can be the first signs of a retinal detachment. 

In this case, you should see an ophthalmologist or go to an eye clinic immediately. As the retinal detachment progresses, a black shadow appears that moves from the periphery toward the center of the visual field. 

As the condition progresses, it can lead to blindness in the affected eye. In terms of differential diagnosis, sudden onset of black spots or streaks may indicate a vitreous hemorrhage. In about 30 to 40 percent of cases, a vitreous hemorrhage is accompanied by a retinal defect.

Small hemorrhages in the vitreous body can be caused by various factors, such as:

• External trauma
• Vitreous detachment
• Diabetic retinopathy 
• Age-related macular degeneration

A vitreous hemorrhage can also occur during a subarachnoid hemorrhage (Terson syndrome). Depending on the size of the hemorrhage, it may appear as a “rain of ashes.”

Vitreous degeneration (destruction of the vitreous body) is an age-related process in which the vitreous body liquefies. This leads to the separation of the liquid and fibrous components of the vitreous body. As a result, opacities may develop in the vitreous, which affected individuals perceive as bothersome floating specks.

Vitreous inflammation (vitritis) can occur in both chronic and acute forms. Due to the vitreous’s structure and blood supply, inflammation of the vitreous is rather rare, but not impossible. The most severe form of inflammation is endophthalmitis, in which other parts of the eye’s interior are also affected.

Possible causes of vitritis include bacteria, viruses, and fungi: 

These can enter the vitreous body in the following ways:

• Through external factors 
• Through surgical procedures

Patients without any significant underlying medical conditions usually suffer from bacterial vitreous inflammation. Patients with immunodeficiency (AIDS patients, patients with tumors, patients who have undergone an organ transplant) may also develop fungal vitreitis (Candida species).

In addition to direct routes of transmission, indirect transmission (sepsis) may also occur.

Depending on the type of pathogen and the patient’s immune system, physicians classify vitreitis as acute, subacute, or chronic. 

Acute vitreitis usually manifests in patients as a dull pain in the eye. Pain relievers generally cannot alleviate this pain. In cases of vitreitis, the conjunctiva is also severely reddened.

Chronic vitreous inflammation is generally less severe.

The doctor treats the condition based on its cause. If the vitreous inflammation is caused by specific pathogens, treatment is based on an antibiogram.

In synchisis scintillans (sparkle vision, spintheropia, Danziger’s goldwater), cholesterol crystals are deposited in the vitreous body. 

In addition to cholesterol deposits, the amino acids tyrosine and leucine, as well as calcium phosphate crystals, can form in the vitreous body. These lead to this asymmetrical condition.

Synchisis scintillans is easily confused with asteroid hyalosis. Synchisis scintillans occasionally occurs following vitreous hemorrhage or inflammation. In most cases, however, the cause is unknown.

Persistent Hyperplastic Primary Vitreous (PHPV)

The term PHPV (persistent hyperplastic primary vitreous) refers to a congenital malformation. In this condition, the embryonic primary vitreous has not regressed. Experts therefore refer to this phenomenon as a developmental disorder. However, it is a very rare disorder.

There are two different forms of PHPV:

• Anterior PHPV
• Posterior PHPV

In the posterior form of PHPV, the embryonic tissue persists in the posterior region.

In the anterior form of PHPV, a connective tissue plate forms that has a whitish color. This plate is located behind the pupil, causing those affected to perceive a white pupil (amaurotic cat’s eye). 

Changes occur in the lens. Fat tissue and cartilage also form in the area of the lens.

Posterior PHPV can lead to a loss of visual acuity, which depends on the severity of the retinal detachment. In anterior PHPV, the lens may develop into a cloudy membrane.

Vision loss is often unavoidable in cases of persistent hyperplastic primary vitreous. Even with surgery, doctors are often only able to save the eye.

Retinal and vitreous diseases encompass a broad spectrum of changes in the eye that are often age-related but can also be triggered by diabetes or an infection. Typical changes involve the vitreous, where collagen fibers and hyaluronic acid undergo alterations, causing the vitreous to appear cloudy. Vitreous detachment or posterior vitreous detachment can cause the vitreous to separate from the retina, leading to the perception of flashes of light. In some cases, bleeding occurs within the vitreous or a vitreous hemorrhage develops, which significantly impairs vision. Inflammation of the vitreous, such as vitritis, can also impair the function of the retina.

Severe cases can lead to retinal detachment or even multiple retinal detachments, which is why early diagnosis is crucial. Retinal diseases and vitreous diseases are often closely related, especially when the vitreoretinal boundary membrane is affected. Additionally, membrane structures can form within the vitreous cavity, obstructing the path of light rays as they travel toward the retina. In advanced cases, the vitreous is surgically removed, and a vitreous substitute may be implanted to maintain stability within the eye.

The lens and the pupil also play a role in the perception of visual disturbances, as they regulate the amount of light entering the eye. The primary vitreous changes over the course of a person’s life and loses its original consistency, thereby increasing the risk of vitreous disease. Vitreous hemorrhages occur more frequently, particularly in diabetic patients. Modern therapies now allow for targeted treatment, such as the removal of foreign material or the stabilization of the retina. Overall, the earlier changes are detected, the better complications can be prevented and visual function preserved in the long term.