Posterior vitreous detachment (PVD)

Summary

Posterior vitreous detachment (PVD) is the separation of the vitreous membrane from the neurosensory retina. This is a very common condition amongst older patients, due to natural changes in the vitreous fluid that occur with ageing. Whilst PVD itself does not cause permanent vision loss, it is essential to rule out more serious associated conditions such as a retinal tear or detachment.

Aetiology

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As people age, the vitreous fluid in the eye becomes less viscous, and therefore does not hold its shape as well. The vitreous gel liquefies with age (’synchysis’) to form fluid-filled cavities, and then condenses (’syneresis’).

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The vitreous fluid can therefore pull the vitreous membrane away from the retina, towards the centre of the eye. A rupture develops in the vitreous membrane (the membrane separating the rear of the vitreous from the retina, also known as the ‘posterior hyaloid membrane’), enabling vitreous fluid to flow into the retrovitreous space, separating the vitreous membrane from the retina.

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Traction of the vitreous at a site where the vitreous is firmly adhered to the retina can produce a retinal tear, and possibly subsequent retinal detachment.

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Epidemiology

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Risk factors for PVD:

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• Increased age – PVD occurs in more than 75% of people aged 65 years and older. It affects most patients by their 80s.

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• Myopic eyes (near-sighted eyes) – the myopic eye has a longer axial length than an emmetropic eye (the medical term for 20/20 vision), thus myopic individuals are at increased risk of developing PVD

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PVD usually occurs spontaneously, but it may be triggered by events such as trauma, panretinal photocoagulation, cataract surgery and uveitis.

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Clinical features

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Symptoms:

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• Many patients will not present with acute symptoms

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• Floaters – the most common complaint. Floaters are caused by vitreous opacities e.g. blood, glial cells or aggregated collagen fibres torn from the optic disc margin

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• A ‘cobweb’ appearing across vision – the vitreous opacities (e.g. blood/glial cells/collagen fibres) move as the vitreous is displaced during eye movement. This casts a shadow on the retina, that is perceived as a grey ‘cobweb’ structure

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• Photopsia (perceived flashes of light), usually in the temporal periphery – caused by physical stimulation of the retina from vitreoretinal traction

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• Blurred vision – often due to dispersed haemorrhage within the vitreous gel

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• Appearance of a ‘dark curtain descending’ (this means there is concurrent retinal detachment)

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Signs:

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• A ‘Weiss ring’ floater on fundoscopy – the detachment of the vitreous membrane around the optic nerve forms a ring-shaped floater called a ‘Weiss ring’

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• The detached retinal membrane may be seen on slit-lamp examination as a crinkled translucent membrane in the mid-vitreous cavity

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• Presence of red blood cells in the anterior vitreous indicates vitreous haemorrhage

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In an eye with PVD, the presence of pigment granules (described as ‘tobacco dust’) in the vitreous on slit-lamp examination indicates there has been a retinal tear.

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Diagnosis

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All patients with a possible PVD must be urgently examined by an ophthalmologist, within 24 hours, to exclude a retinal tear or detachment.

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Indirect ophthalmoscopy (ideally with scleral depression) and slit-lamp examination are the preferred examination techniques to diagnose PVD (and rule out retinal tears/detachment). B-scan ultrasound can demonstrate the extent of the PVD, and OCT can show separation of the rear of the vitreous from the retina.

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Patients are usually re-examined within 2-6 weeks to assess again for retinal breaks. It is possible for a new retinal tear or detachment to develop during the few weeks following a PVD.

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In any patient with PVD, it is essential to rule out retinal tear, retinal detachment or vitreous haemorrhage, as these conditions can result in permanent loss of vision.

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Management

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• PVD alone does not cause any permanent loss of vision; the visual prognosis is good. The symptoms gradually improve over a period of 〜6 months, thus no treatment is required

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• Patients must be advised to return immediately if there are increasing flashers, floaters or shadows in their vision

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• There is no medical treatment for a PVD

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• If, however, a patient has an associated retinal tear/detachment, surgery is required

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References

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1. Salmon, John F., and Jack J. Kanski. Kanski’s Clinical Ophthalmology: A Systematic Approach. Ninth Edition, Elsevier, 2020.

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2. ‘What Is a Posterior Vitreous Detachment?’ American Academy of Ophthalmology, 22 Nov. 2022, https://www.aao.org/eye-health/diseases/what-is-posterior-vitreous-detachment.

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3. Ahmed, Faryal, and Koushik Tripathy. ‘Posterior Vitreous Detachment’. StatPearls, StatPearls Publishing, 2022. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK563273/.

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4. Retina Gallery. https://www.retinagallery.com/displayimage.php?album=search&cat=0&pid=6425#top_display_media

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