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RETINAL DETACHMENT - VITREOUS DETACHMENT

What is Retinal Detachment ?

Retinal detachment: The retina comprises two layers, the neuro-sensory retina and the underlying retinal pigment epithelial layer. A detachment (known as rheagmatogenous) occurs when a tear or hole develops in the neural layer. Fluid from the vitreous then enters through the tear or hole causing the two layers to separate. There is then progressive loss of vision affecting that part of the retina. The speed of loss of vision depends on the size of the tear or hole and its position. A large tear at the top of the retina will result in rapid and complete retinal detachment with loss of vision. A small hole in the lower part of the retina may be undetected causing only a small area of upper visual field loss. Retinal detachment can also occur due to traction, when the retina is pulled inwards by scar tissue forming within the vitreous of the eye.

Posterior vitreous detachment: The vitreous is a transparent gel which fills the compartment of the eye behind the lens. Up until middle life it is in close contact with the retina of the eye. The vitreous has no true function after birth. During foetal development it performs an important scaffold for the developing eye. During middle life the vitreous gel begins to degenerate and eventually lose its structure. The normal vitreous has tiny floating strands within it which all of us can see when looking up at a bright sky as background. In middle age, generally between the age of 55 and 70 the vitreous eventually collapse inwards and peels away from the retina. This may occur uneventfully and be unnoticed. However, more dramatically it presents with the sensation of seeing flashing lights particularly at night as the retina is pulled on by the detaching vitreous. There is then relatively sudden onset of seeing a moving black line or blob within the vision. Many people describe this as seeing a "fly" moving across the vision. The floaters eventually will settle, but they take several months and can be troublesome. Short sighted people with a larger eye often develop a vitreous detachment at a younger age. Trauma to the eye, either direct or following head trauma for example after a car crash can result in vitreous detachment at an earlier age.

How does Retinal Detachment occur ?

Holes and tears may form spontaneously in an area of degeneration called lattice. This is more common in very short-sighted people. Retinal degeneration affecting the peripheral retina can also run in families. Tears usually occur however, as a result of vitreous detachment occurring in later life. When the vitreous separates (posterior vitreous detachment ) it may pull a piece of retina. This may also result in a haemorrhage into the vitreous which causes black floaters and loss of vision. Trauma to the eye can cause a retinal detachment by causing a split to develop at the point the retina attaches in the mid part of the eye. This is called a retinal dialysis. Diabetes which causes vitreous haemorrhages and scar tissue can result in traction retinal detachment. Severe trauma can also result in haemorrhage and scar tissue which forms traction detachment.

Treatment Involved for Retinal Detachment

In rheagmatogenous detachment the holes or tears must be sealed up to allow the retina to reattach. During the operation the fluid may also be drained from underneath the detached retina either internally or externally. An external operation involves apply a freezing probe to the outer surface to the eye over the area of the tear to create an adhesion which seals the tear. This is combined with sewing a plastic or silicone sheet (an explant) onto the external surface of the eye, overlying the tear. This tends to act as a "bolster" to close the tear. An injections of air or long lasting gas may also be injected into the eye to tamponade the tear from within. The internal approach involves removing the vitreous gel and filling the cavity with gas and in some more serious cases with silicone oil. The tears can either be lasered internally with a laser-light pipe or externally with cryotherapy.

It is always important to examine carefully the fellow eye which may have similar tears or areas of degeneration which may result in the future with detachment. These would then be treated with either laser or cryotherapy at the time of the operation for the eye with the detachment. When vitreous haemorrhage is present an internal approach is usual. This method is also necessary when there is traction detachment. The operation is generally done under general anaesthetic and involves a stay in hospital. It may be necessary for the patient to position their head in a certain way following surgery to maximise the effect of an internal gas or air bubble. Antibiotics and anti-inflammatory drops are necessary after the operation.

There is no treatment necessary for vitreous detachment. However it is very important to see an eye specialist for a careful examination of the retina. In a few cases the vitreous pulls a piece of retina when it detaches and causes a retinal tear and / or haemorrhage for tearing of retinal blood vessels. If untreated a retinal tear is likely to result in the serious condition of retinal detachment.

After Treatment for Retinal Detachment

The amount of visual recovery following retinal detachment surgery depends most principally whether the macular area in the centre of the retina was detached before the operation. Visual recovery is usually good when the macular has not been detached. If the macular was involved the recovery of vision is dependant on how long it has been detached. If it is only a few days and a young person then returning to an almost normal level of vision may occur. However this often takes many weeks. Vision can in fact progressively improve over a number of months following retinal detachment surgery. However if the detachment has been present for many weeks particularly in an older individual, visual recovery may not be good.

The retina may re-detach or fail to attach after the first operation. Failure may be due to either retinal tears failing to close or to scar tissue forming on the surface of the retina. This is a condition called proliferative vitreo retinopathy (PVR). When this occurs a further operation is necessary, usually an internal approach. Rarely even a second operation fails.

If Retinal Detachment is Left Untreated

Small detachments, particularly in the lower half of the retina may "wall off" and be undetected. They may then be detected at a routine examination by an optician. However most detachments, if not treated, will result in loss of vision. The other eye may have degeneration or retinal tears, which do not produce symptoms. If not treated this would lead to a detachment occurring in the second unaffected eye. An examination following symptoms of retinal detachment is therefore very important.