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

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’).

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.

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.

Epidemiology

Risk factors for PVD:

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

Symptoms:

• Many patients will not present with acute symptoms
• 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
• 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
• Photopsia (perceived flashes of light), usually in the temporal periphery - caused by physical stimulation of the retina from vitreoretinal traction
• Blurred vision - often due to dispersed haemorrhage within the vitreous gel