Synonyms: posterior vitreous detachment (PVD), vitreous separation
The vitreous makes up about 80% of ocular volume. It consists mostly of water (99%), the remainder being hyaluronic acid and collagen fibrils. These fibrils connect the vitreous to the retina. Some areas (at the disc, the fovea and around the periphery anteriorly) are more adherent than others. The concentration of hyaluronic acid decreases with age and the vitreous liquefies (synchysis) and reduces in volume, causing it to fall away from the retina and cause a vitreous detachment. In doing so, it may pull on the retina (particularly if one of the more adherent areas has become detached) and a retinal tear may result. If fluid seeps under a retinal tear, a retinal detachment ensues.
Its importance lies in the fact that it is common and, although not serious, the symptoms and signs are similar to those of a retinal detachment.
- Most common cause of flashes and floaters
- Found in about 75% of over 65 year olds
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- Single (usually) or multiple floaters (dots, spots, or wispy "lace" objects floating across vision).
- The floaters are often described as either a circle, ovoid or a bent line, depending on the completeness of the detachment. A shower of black specks is more suggestive of a vitreous haemorrhage (which may be associated with retinal detachment).
- Photopsia (an ocular flash) occurs if the vitreous separation exerts traction on the retina.
- This is a painless condition with no visual impairment (only a nuisance hindrance due to mobile floaters).
Unless there is a large associated retinal detachment, signs are only likely to be elicited on slit-lamp biomicroscopy. Findings may include:
- A Weiss' ring: this is the condensed, thickened posterior surface of the vitreous that has now become visible as it has pulled away from the optic disc. It looks like a thin irregular ring of translucent material floating in the vitreous.
- Occasionally, a haemorrhage is noted.
Most floaters in patients over 50 are due to benign vitreous syneresis (liquefaction). However, a full slit-lamp examination is mandatory to confirm the diagnosis and rule out retinal breaks or tears. If a haemorrhage is noted, an ultrasound scan will also be carried out (this simply involves placing a small probe gently on the closed eyelid of the patient; it is done in clinic there and then). If there is a tear or detachment, a visual field may be done to ascertain the extent of visual loss.
- 10% of patients presenting with vitreous detachment have a retinal tear (half of these have multiple tears).
- A retinal tear can be sealed in the early stages by laser therapy, thus preventing liquid vitreous seeping through the hole and causing a retinal detachment.
- In an ideal world, highly symptomatic patients would be followed up 4-6 weeks following presentation. This generally does happen with high-risk patients (previous detachments, high myopes, recent surgery or trauma). Patients with haemorrhages will also need following up. For most, however, retinal detachment advice is given and the patient is discharged.
- There are further episodes of new floaters (particularly a shower of black specks)
- There are new episodes of flashes or the flashes worsen (particularly if visible in broad daylight)
- There is any deterioration of vision
Retinal tear with or without detachment. This complicates about 10% of cases on presentation and a further 2-5% of patients in the weeks that follow. Occasionally, vitreous detachments can be associated with a vitreous haemorrhage if the part that has become detached happened to overlie a blood vessel.
The vast majority of patients recover fully from their symptoms. The detachment doesn't repair itself but the associated symptoms subside and there are no complications.
- Most patients gradually become accustomed to the floaters and only notice them if they look at a very bright background and attempt to focus on them. This may takes months or longer.
- Flashes tend to resolve gradually as the vitreous becomes completely loose and stops tugging on the retina. Very occasionally, flashes persist that are so troublesome that surgery (vitrectomy) may be considered. This is not without risks however.
- A vitreous haemorrhage may occur if the detachment involves a retinal vessel. This tends to clear spontaneously but very large haemorrhages may take a very long time and may require surgical intervention.
Further reading & references
- RNIB; Posterior vitreous detachment
- Jackson TL; Moorfields Manual of Ophthalmology, Mosby (2008)
- Denniston AKO, Murray PI. Oxford Handbook of Ophthalmology (OUP), 2009.
|Original Author: Dr Olivia Scott||Current Version: Dr Olivia Scott|
|Last Checked: 18/11/2009||Document ID: 1059 Version: 24||© EMIS|
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