The vitreous is the clear, gel-like substance that fills the space between the lens and the retina.  This gel aids in keeping the retina positioned against the back wall of the eye.

Causes

With aging, calcium and other particles can spontaneously settle out within the vitreous. This causes the formation of small white precipitates that become suspended within the gel. The precipitates that develop can best described as "floaters" in the vitreous. 

Additionally, after experiencing an inflammatory event in the eye, an animal can develop these precipitates in conjunction with a degeneration of the vitreous gel itself. This degenerative condition, called syneresis, results in liquefaction of the gel, and on examination, the appearance can be likened to a small toy that depicts a "snow village scene," that when shaken, snowflakes are seen to swirl about.

Signs

Typically this is an incidental finding during an eye examination. Neither asteroid hyalosis nor syneresis cause any significant impairment of vision. There may be no perceptible difference in the animal's vision, or it may appear to cause functional changes due to the clouding of the vision in others. Some pets, in very severe cases, may show trouble with their vision.

Treatment

Treatment of asteroid hyalosis is rarely recommended. If a severe case is considered to be interfering with an animal's vision (rare), the treatment recommendation would be surgical removal of the vitreous (vitrectomy).

Prognosis

The condition may or may not progress and is usually self-limiting and benign. Animal's with syneresis have the potential to subsequently develop a retinal detachment. In patients with severe syneresis, particularly those considered as having the potential to develop a retinal detachment, a procedure may be recommended to prophylactically pre-empt such as event (retinopexy). Certain dog breeds, for example, are at a relatively higher risk for developing retinal detachment (Bichon Frise, Boston Terrier).