Vitreous cysts are rare diseases that form cystic lesions floating or fixed within the vitreous cavity. They were first reported by Tansley in 1899 as “irregular spherical cysts with pigment lines on the surface.” They are considered an “ocular curiosity” due to their rarity, and may be found incidentally in normal eyes or associated with other ocular diseases.
Age of onset ranges from 5 to 68 years, with most patients being young individuals in their teens to twenties, though cases under 10 years or over 40 years have also been reported. 2) The majority are unilateral and usually asymptomatic, often discovered incidentally during examinations for other purposes such as strabismus or amblyopia. 1)
The ICD-10 code is H43.89 (other disorders of vitreous).
Vitreous cysts are so rare that they are called an “ocular curiosity” in ophthalmology. The exact prevalence is unknown, but reports are mainly case reports, and large-scale epidemiological data do not exist. Most are discovered incidentally.
Vitreous cysts are usually asymptomatic and often do not affect vision. When the cyst enters the visual axis and obstructs the light path, the following symptoms may be noticed.
Congenital Cyst
Color: Non-pigmented, translucent cyst with a pearl-gray to yellow-gray appearance.
Surface: Smooth and mobile. Sessile or pedunculated.
Location: Often anterior to the optic disc, in the area of Cloquet’s canal.
Associated findings: May be accompanied by Mittendorf dot or Bergmeister papilla.
Acquired Cyst
Color: Pigmented (brown) or non-pigmented.
Origin: Most are pigmented cysts derived from the pigment epithelium of the iris or ciliary body.
Mobility: Typically free-floating, moving with eye movements.
Size: Ranges widely from 0.15 to 12 mm. 1)
Morphologically, cysts can be spherical, oval, or lobulated, with a smooth or crenated surface. During examination with an indirect ophthalmoscope, the cyst may be observed to move with the patient’s eye movements.
On OCT, a thin hyperreflective cyst wall and hyperreflective septa dividing the interior into multiple compartments (multi-lobular structure) may be seen. 1) B-mode ultrasound has reported that the echogenicity of the cyst wall is similar to that of the posterior lens capsule. 1)
Usually unilateral, but bilateral cases have been reported, especially when associated with retinitis pigmentosa. Multiple cysts in one eye can also occur.
Vitreous cysts are broadly classified as congenital or acquired.
They originate from remnants of the hyaloid vascular system during embryonic development. The hyaloid artery loses function around the sixth month of gestation and normally regresses before birth; incomplete regression is thought to lead to cyst formation. They are often located along Cloquet’s canal or near the optic disc, and may be found together with Mittendorf’s dot or Bergmeister’s papillae.
They are usually stable, non-progressive, and rarely affect vision.
They occur secondary to the following diseases or conditions:
Vitreous cysts are often first discovered during a clinical examination with a slit-lamp microscope or fundus examination. Systematic testing is necessary to differentiate them from other infectious or malignant diseases.
Be sure to check the following medical history:
The characteristics of the main imaging tests are shown below.
| Test | Purpose / Findings |
|---|---|
| B-mode ultrasound | High echo of cyst wall, anechoic interior. Presence of scolex. |
| OCT | Detailed assessment of cyst wall and internal structure1) |
| Ultrasound biomicroscopy | Exclude abnormalities of ciliary body and posterior iris |
The following are performed to rule out parasitic infection or malignancy:
A definitive diagnosis of primary vitreous cyst is made by excluding trauma, surgery, infection, and inflammation, and by identifying a translucent or pigmented cystic structure within the vitreous cavity. 1)
Differentiation is important because pigmented cysts resemble malignant melanoma in appearance. B-mode ultrasound confirms internal acoustic hollowing, and orbital/head MRI and abdominal ultrasound check for metastasis. Additionally, serological tests for parasites such as cysticercosis and echinococcosis are performed to rule out infection.
Regular observation and follow-up are the basics to monitor for changes in cyst characteristics or the patient’s visual acuity. For asymptomatic cysts located off the visual axis, therapeutic intervention is not required. 1)
When symptoms are significant, the following treatment options are available.
In severe vision loss cases resistant to medical treatment, cyst removal via vitrectomy may be necessary. In young phakic patients, there is a risk of cataract development.
For pigmented cysts causing severe impairment, a combination of laser and vitrectomy may be recommended, as laser alone can cause pigment concentration. 1)
Several hypotheses have been proposed for the pathogenesis of vitreous cysts, and a single mechanism cannot explain all cases.
During the embryonic period, the hyaloid artery (hyaloid vascular system) loses function around the sixth month of gestation and normally regresses and disappears before birth. Incomplete regression is thought to contribute to cyst formation. Cloquet’s canal is a tubular structure formed when the regressed primary vitreous is compressed into the center of the vitreous cavity, and it is a common site for congenital cysts. Congenital cysts are pathologically defined as choristomas of the primary vitreous system.
Three main hypotheses regarding the pathogenesis are described below.
Non-pigmented cysts have been reported to show immunohistochemical staining findings suggestive of glial cell origin (positive for GFAP, S100, and synuclein; negative for melanocyte markers, epithelial markers, and macrophage markers).
Some opinions suggest that pigmented cysts originate from the iris, while non-pigmented cysts originate from remnants of the hyaloid artery. 1)
The internal multi-compartment structure with highly reflective septa observed on OCT is presumed to be formed by residual epithelial cells. The finding that the cyst wall echo on B-mode ultrasound is similar to that of the posterior lens capsule suggests an association with lens epithelial cells. 1)
Trauma can damage the pigment epithelium of the ciliary body and lead to pigmented cysts. Other proposed mechanisms include vitreous reaction to underlying retinal degeneration, rupture of a ciliary body adenoma into the vitreous, and extension of cystic proliferation at a coloboma site into the vitreous cavity.
In retinitis pigmentosa, the frequency of vitreous cysts and asteroid hyalosis is known to be higher than in healthy individuals.
Lu et al. (2024) performed multimodal imaging evaluation combining OCT, scanning laser ophthalmoscopy (SLO), fundus color photography, multicolor imaging, and infrared reflectance (IR) imaging in a 37-year-old male with primary pigmented vitreous cyst.
OCT examination revealed multiple hyperreflective septa inside the cyst, with a multi-lobular structure of the lumen. This is the second reported case where OCT captured the internal structure of the cyst in detail. Infrared reflectance imaging showed hyperreflective areas due to melanosomes, supporting the possibility of pigment epithelial origin. B-mode ultrasound showed that the echo brightness of the cyst wall was equivalent to that of the posterior lens capsule, suggesting an association with lens epithelial cells. 1)
The patient maintained good visual acuity during 6 months of follow-up, and observation without treatment intervention is ongoing. The combination of multimodal imaging is expected to contribute to understanding the pathology of this rare disease. 1)
Al Qattan et al. (2024) reported a 3 mm pigmented lobulated cyst in the anterior vitreous of the left eye in a 2-year-6-month-old girl with tetralogy of Fallot and high myopia (-14D).
In a highly myopic eye with posterior staphyloma, the cyst floated in the anterior vitreous and remained stable without enlargement during 2 months of follow-up. An association between high myopia, posterior staphyloma, and vitreous cyst was suggested, but the pathophysiology remains unclear. Additionally, the patient had multiple systemic abnormalities including tetralogy of Fallot, double-row teeth, low nasal bridge, and sternal protrusion, requiring differentiation from known syndromes such as Carpenter syndrome. Such systemic involvement has not been previously reported, and genetic testing was recommended. 2)
Further case accumulation and research are needed regarding the association between vitreous cysts and systemic diseases.
