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The amount of nerve tissue (seen in the rim of the optic disc), slowly declines with age. However in glaucoma this happens more rapidly. When looking in the eye it is possible to see the “cup to disc” ratio (how big the ‘cup’ or hollow is in relation to the overall disc). In a healthy eye the ratio is usually low (0.3 or less), but in an eye with glaucoma this may be 0.7 or more. There is no fixed ratio that means the eye has glaucoma – however, the higher the ratio, the higher the risk.

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Why it matters
2% of all visual impairment worldwide is due to glaucoma and it is the second leading cause of blindness. Some groups are at higher risk of glaucoma such as people over 40 years old, those of African descent and those with close family members who have glaucoma. The effect on the person is a gradual loss of peripheral vision and ‘blind spots’ which gradually make day to day life more difficult. There is no current treatment to restore sight loss from glaucoma, although treatments that stop or slow the disease are available. Symptoms are not usually noticed until late in the disease which is often too late to prevent permanent damage. Therefore picking up signs (a change in the optic nerve, an abnormal visual field result or a high pressure in the eye) can help detect the disease before major sight loss happens and allow treatment to be started to prevent further loss of vision.

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Optic nerve swelling and Papilloedema

Within the brain, the optic nerve is surrounded by a space filled with cerebrospinal fluid. If the pressure in this space rises, for example when the space is reduced by the presence of a brain tumour, the effect can often be seen when looking at the optic disc and this can aid rapid diagnosis.

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The two main signs of papilloedema that be seen by looking at the optic disc are, firstly, the absence of a spontaneous venous pulsation (pulsation of the blood vessels), seen when the intracranial pressure is within normal range. While the presence of the pulsation is a reassuring sign, if it is absent it does not indicate that there is necessarily a problem. The second sign is when the distinct margin (the edge of the optic disc) becomes blurred and the ‘cup’ disappears.

Why it matters
Headaches are common and usually benign.  However certain symptoms would alert a clinician that they need to rule out a more serious problem. Being able to see and differentiate between a normal nerve and a swollen nerve has major implications on the level of investigation and urgency of potential treatments. It can be the first sign of a serious and fatal problem and if picked up promptly could be life saving. A wide variety of conditions can cause papilloedema such as a brain tumour or brain haemorrhage, acute mountain sickness, Lyme disease and it can also occur as a side-effect of some drugs.

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Pale optic disc

The optic disc is usually orange or pink. However certain conditions that affect the optic nerve can affect the colour of the optic disc, usually resulting in a pale disc or “optic disc pallor”. This can be a normal variation but may be a sign of a problem. This could be in the nerve fibre layer of the retina that feeds into the optic disc, or damage to the optic nerve itself such as inflammation, known as papillitis.

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Why it matters

A pale disc can mean that a potentially serious underlying cause needs to be investigated, particularly if it is associated with visual symptoms such as reduced visual acuity, pain when moving the eye, reduced contrast sensitivity, visual field defects and colour perception changes. A wide variety of conditions can lead to a pale optic disc such as multiple sclerosis, tumours and as a side-effect of some drugs. Many of the underlying causes can be treated if identified promptly.

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Peek, Peek Acuity and Peek Retina are trading names of Peek Vision Ltd, a registered company (09937174) in England and Wales.

Peek Vision Ltd is 100% owned by The Peek Vision Foundation (registered charity number 1165960), a company limited by guarantee registered in England and Wales (company number: 9919543). Registered office: Kings Parade, Lower Coombe Street, Croydon, Surrey, England, CR0 1AA.