Synchysis scintillans

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Synchysis scintillans


Disease Entity

Synchysis scintillans or cholesterolosis bulbi[1] is an ocular condition where there is accumulation of cholesterol crystals in the vitreous humor of the eye. Synchysis scintillans appears as small white floaters that freely move in the posterior part of the eye, giving a snow globe like effect. It is asymptomatic and untreatable and is often an incidental finding. On fundus examination, it is seen as a shower of golden particles in the vitreous.


Disease

Benson, in 1894, was the first to describe accurately and to differentiate synchysis scintillans [2]from asteroid hyalosis. There was some controversy about its existence even in 1983.[3] It is an asymptomatic condition, often found incidentally, where yellow crystals are seen floating in the vitreous. In synchysis scintillans, the vitreous liquifies in a process known as syneresis. Clinically, the highly reflective crystals are dispersed with the movement of the eye. Over time, the crystals will settle to the gravity-dependent portion of the vitreous cavity. This is often confused with asteroid hyalosis.

Etiology

Synchysis Scintillans or Cholesterolosis Bulbi in the vitreous of an eye seen with smartphone fundus videography
Synchysis Scintillans or Cholesterolosis Bulbi in the vitreous of an eye seen with smartphone fundus videography

Synchysis scintillans is postulated to be due to a degenerative process in the vitreous. This can happen in any age group due to other ocular conditions like vitreous hemorrhage, hyphema, retinal detachment or chronic uveitis.[4] The crystals consists of degenerative material(cholesterol) not attached to the vitreous framework. Rarely, when vitreous gains access to the anterior chamber (e.g., in aphakia or subluxation), a synchysis scintillans of the anterior chamber can also be seen.

Synchysis scintillans has the following clinical properties:

  • It is golden in color both to retroillumination and to direct view.
    • Usually it is unilateral and most common in men in their fourth or fifth decade.
    • It frequently follows an intravitreal (within vitreous body) hemorrhage.
    • The material settles inferiorly when the eye is immobile.
    • When in the anterior chamber, it disappears (melts) on the application of heat (e.g., as with a sun lamp).
  • Histologically, clefts represent the sites of dissolved-out cholesterol crystals within the vitreous body.

Epidemiology

Synchysis scintillans is seen in a younger age group compared to asteroid hyalosis. There is no race or sex predilection. They also exhibit a bilateral presentation. Asteroid Hyalosis usually unilateral and more common in men. Synchisis scintillans is a rare condition that occurs in severely diseased eyes.

Risk Factors

  • Vitreous Hemorrhage
  • Diabetic Retinopathy
  • Chronic Uveitis
  • Retinal Detachment
  • Hyphema
  • Ocular trauma
Traumatic uveitis and Hyphema can lead to Synchysis Scintillans
Traumatic uveitis and Hyphema can lead to Synchysis Scintillans

General Pathology

Synchysis scintillans is rare and due to degenerative processes in the vitreous resulting in formation of cholesterol crystals. It is usually noted in the vitreous cavity, but there were reported cases of anterior chamber synchysis scintillans due to lens subluxation[5] and anterior mobilization of the vitreous through the pupillary area.[6]

Pathophysiology

Synchysis scintillans is associated with the advanced stages of diabetic retinopathy, but the exact pathogenesis is unknown. Synchysis scintillans may occur after chronic uveitis, chronic or recurring vitreous hemorrhage or trauma. Crystal-like opacities may be observed in the vitreous as the bulk hemorrhage dissipates, or they may appear as flat, freely mobile, brown-white, refractile bodies in the anterior chamber.

Chemical studies demonstrate the presence of cholesterol crystals in these opacities, hence the condition is sometimes referred to as cholesterolosis bulbi. Synchysis scintillans is usually noted in the vitreous cavity, but there are reported cases of anterior chamber synchysis scintillans due to lens subluxation and anterior mobilisation of the vitreous through the pupillary area. The condition is also seen in degenerating eyes before the onset of phthisis bulbi.

Diagnosis

Fundus examination with indirect ophthalmoscopy or using a 90D lens in slitlamp biomicroscopy is diagnostic. It has to be differentiated from asteroid hyalosis. In synchysis scintillans the vitreous is filled with cholesterol crystals. Unlike asteroid hyalosis, these crystals are not suspended within the vitreous but instead float freely in the vitreous space. When the globe moves, the crystals appear in the center of the vitreous body. This clinical picture may resemble asteroid hyalosis, but after a few seconds the cholesterol crystals will sink toward the bottom of the cavity. A-mode images display characteristic flickering spikes from the reflections of these crystals.

Sometimes, synchysis scintillans may present in the anterior chamber often after aphakia and vitreous prolapse. This may even be maquerade as phacolytic glaucoma.[7]

Comparison between Synchysis Scintillans and Asteroid Hyalosis

  • Compare Asteroid Hyalosis and Synchysis Scintillans
    Compare Asteroid Hyalosis and Synchysis Scintillans
    Classically, asteroid hyalosis presents as “stars in the night sky”. Asteroid bodies “sway” within the vitreous with eye movement, but they always return to their origin.
  • Ocular asteroids must be distinguished from the more common typical vitreous floaters, which are usually fibrillar or cellular condensates.
  • The density of asteroid hyalosis does not correlate with visual dysfunction. If a patient presents with significantly diminished acuity, asteroid hyalosis is not to blame. Continue examining the patient until the actual aetiology is found.
  • Synchysis scintillans is the deposition of highly refractive cholesterol crystals in the vitreous of highly diseased eyes.
  • Synchysis scintillans is seen as a golden shower during the movements of the eye.
  • The cholesterol crystals of synchysis scintillans are not attached to the vitreal framework and therefore tend to settle out inferiorly after eye movement.
  • Asteroid hyalosis and synchysis scintillans are uncommon conditions. Asteroid hyalosis has been reported to have an association in patients with diabetes mellitus and to a lesser extent with systemic arterial hypertension and atherosclerotic vascular disease.
  • Synchysis scintillans is often associated with previous or chronic vitreous haemorrhage secondary to neovascularisation or trauma.

Asteroid Hyalosis is characterized by the presence of small spherical opacities of yellowish white color, composed of lipids, calcium and phosphorus. This condition is usually unilateral and more common in men. Synchysis Scintillans is characterized by the presence of highly refractive vitreous opacities, flattened, brown or gold colored, composed of cholesterol. This condition occurs at an earlier age than asteroid hyalosis and is usually bilateral.

Management

Uveitis or vascular work-up may be required to rule out either active or lingering inflammation, which can produce vitritis. Because vitreous haemorrhage is associated with degenerative processes that can raise intraocular pressure, patients must also be monitored for glaucoma.

A therapeutic strategy which targets oxidative stress may be effective in the treatment of synchysis patients.[8] With the exception of pars plana vitrectomy for cases with poor visual outcome, there is no effective management option for this condition.

Complications

Synchysis Scintillans is asymptomatic and without any complications. But often, they may be the result of chronic uveitis, lens dislocation or vitreous hemorrhage. There may be inflammation or raised Intra Ocular Pressure due to these conditions which have to be treated accordingly.[5] They may also be associated with retinal detachment and other conditions due to trauma.

Additional Resources

References

  1. Wand M, Smith TR, Cogan DG. Cholesterosis Bulbi: The Ocular Abnormality Known as Synchysis Scintillans. American Journal of Ophthalmology. 1975;80(2):177-183. doi:10.1016/0002-9394(75)90129-4
  2. Margo CE. Age-Related Diseases of the Vitreous. In: Cavallotti CAP, Cerulli L, eds. Age-Related Changes of the Human Eye. Aging Medicine. Humana Press; 2008:157-191. doi:10.1007/978-1-59745-507-7_8
  3. Potter JW. Synchysis Scintillans, Cholesterosis Bulbi, and Asteroid Bodies: Does Synchysis Scintillans Exist? The Australian Journal of Optometry. 1983;66(6):232-238. doi:10.1111/j.1444-0938.1983.tb03724.x
  4. Brodsky MC. Synchysis Scintillans in a Child. JAMA Ophthalmol. 2015;133(7):e150793-e150793. doi:10.1001/jamaophthalmol.2015.0793
  5. 5.0 5.1 Kumar V, Goel N, Piplani B, Raina UK, Ghosh B. Spontaneous posterior dislocation of nucleus with synchysis scintillans. Contact Lens and Anterior Eye. 2011;34(3):144-146. doi:10.1016/j.clae.2011.02.009
  6. Banc A, Stan C. ANTERIOR CHAMBER SYNCHYSIS SCINTILLANS A CASE REPORT. Rom J Ophthalmol. 2015;59(3):164-166.
  7. Lo K-J, Huang Y-Y, Hsu C-C. Synchysis scintillans mimicking phacolytic glaucoma in a traumatic eye. The Kaohsiung Journal of Medical Sciences. 2019;35(6):382-383. doi:10.1002/kjm2.12050
  8. Bergandi L, Skorokhod OA, La Grotta R, Schwarzer E, Nuzzi R. Oxidative Stress, Lipid Peroxidation, and Loss of Hyaluronic Acid in the Human Vitreous Affected by Synchysis Scintillans. Journal of Ophthalmology. 2019;2019:e7231015. doi:https://doi.org/10.1155/2019/7231015