Understanding retinal detachment surgery

What is retinal detachment?
What causes the retina to detach?
How does retinal detachment affect your sight?
When should you have retinal detachment surgery?

 

What is retinal detachment?

Retinal detachment is a separation of the light-sensitive retina from the eye wall. This usually starts towards the periphery of the retina and spreads centrally. Separation prevents normal retinal function, the patient becoming aware of worsening visual loss, which, if not repaired promptly, will result in permanent visual impairment or even blindness in the affected eye.

It is helpful to know a little about the eye and how it works in order to understand what effect a retinal detachment has on your vision, and how it can be treated.

Anatomy of a normal eye

The wall of the eye is formed by three layers, the retina, the choroid and the sclera.

The retina is the light-sensitive nerve tissue that lines the inner wall of the eye. Rays of light enter the eye, passing through the cornea, pupil and lens before focusing on to the retina. The retina contains photoreceptors which convert these light rays into electrical impulses. In the healthy eye these impulses are sent via the optic nerve to the brain where sight is interpreted as clear, bright, colourful images. The retina can be likened to photographic film in a camera.

If a hole develops in the retina, fluid is able to seep beneath, causing the retinal layers to separate from the eye wall.

The choroid is the underlying vascular (blood vessel) layer of the eye from which the retina receives oxygen and nutrients. When a detachment occurs, the affected part of the retina is unable to function and if it is not re-attached promptly, permanent visual loss may ensue.

The vitreous is the clear jelly-like substance which fills the hollow space behind the lens. As we age this vitreous gel opacifies and shrinks away from the retina. This is very common, occurring in about seventy-five per cent of people over the age of sixty-five.

Separation of the vitreous gel from the retina is known as posterior vitreous detachment or “PVD”. It does not itself cause any permanent loss of vision although floaters may be troublesome. As the vitreous gel is attached to the retina more firmly in some places than others the retina may tear as the gel separates.

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What causes the retina to detach?

Anyone can develop a retinal detachment at any time; it is unlikely that it has been caused by anything you have done. However, some people are at a greater risk than others of developing this condition.

Pre-disposing factors for detachment are:

  • age; posterior vitreous detachment occurs more commonly as we age and it is at the time of PVD that there is the greatest risk of retinal detachment;

  • myopia; short-sighted people (myopes) are much more susceptible because their eyes are larger than average, resulting in a thinner and more fragile retina. Myopes also develop PVD earlier and are more prone to weakness of peripheral retina;

  • trauma; people who have sustained direct trauma to the eye or face may suffer a detachment;

  • cataract surgery; any form of intra-ocular surgery will slightly increase the risk;

  • familial retinal detachment; as a consequence of inherited retinal weakness, although this is rare.

If you have a retinal detachment in one eye you are at an increased risk of developing similar change in the other.

Your fellow eye will be examined to determine the need for preventative laser treatment.

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How does retinal detachment affect your sight?

Common symptoms of posterior vitreous detachment are:

  • flashes of light seen as arcs in the periphery of vision, more noticeable in dim illumination;

  • new floaters which may vary from small spots or “cobwebs” to larger patches of mistiness which flick across the field of vision on eye movement.

Common symptoms of retinal detachment are:

  • a shadow spreading across the vision starting peripherally and moving centrally;

  • blurred or distorted central vision implying involvement of the central macular retina.

Symptoms of retinal detachment or posterior vitreous detachment should be reported as a matter of urgency.

Comparison of a healthy eye and an eye with retinal detachment

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When should you have retinal detachment surgery?

Many retinal detachments constitute a medical emergency. There is a limited window of opportunity to repair the detachment before permanent visual loss is suffered. The aim is to intervene before the detachment has progressed to involve the central macula, which would be perceived by you as a cloud or curtain coming across the centre of your vision.

Whilst peripheral vision will improve following a detachment repair your central vision, if affected, can never fully recover. When the loss of central vision is recent, urgent surgery with prompt re-attachment of the macular retina can achieve substantial central visual improvement.

Occasionally a detachment may be longstanding and its progress limited, such that central vision has been spared. Surgery in these cases is not urgent.

There are a number of ways to treat retinal detachment and the most appropriate treatment for you will be based on the type, location and extent of the detached retina.

The purpose of surgery is to reposition the retina on to the inside wall of the eye. In ninety per cent of cases this can be achieved with a single operation. The reason to proceed with surgery is to prevent blindness.

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