Diabetic retinopathy does not usually affect vision until it is fairly advanced. Studies have shown that early diagnosis and treatment of diabetic retinopathy greatly reduce the risk of visual loss; ideally treatment needs to be carried out before vision is affected.
Therefore, it is essential to attend annually for digital retinal screening,either through the GP's surgery or at an accredited optometric practice, so that any changes to the retina can be diagnosed and referred for treatment if necessary.
It has been shown that strict blood glucose and blood pressure control and not smoking can all help to reduce the risk of developing sight threatening diabetic retinopathy.
Diabetic retinopathy can be graded according to how severe it is:
Non Proliferative Diabetic Retinopathy
This is common in those who have had diabetes for a long time. The retinal blood vessels may bulge slightly to form microaneurisms. There may be signs of blood vessels leaking fluid to form exudates, or blood to give haemorrhages. People with non proliferative diabetic retinopathy need careful observation to ensure the condition does not progress and worsen. There is usually no reduction in vision as the macula is unaffected. |
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Non Proliferative Diabetic Retinopathy
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Maculopathy.
The macula area can be affected by diabetes; vessels near the macula can leak and bleed to cause macular swelling (oedema). This leads to a worsening of central vision, and can require laser treatment to seal leaking vessels. Maculopathy is the main cause of permanent loss of sight in diabetics, but never leads to total blindness as peripheral vision is usually preserved. Diabetics who notice a reduction in vision therefore need prompt assessment. |
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Diabetic Maculopathy
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Proliferative Diabetic Retinopathy
As diabetic retinopathy progresses, it can cause the blood vessels in the retina to be permanently damaged, leading to the retina not receiving enough oxygen.
The retina tries to heal itself by forming new blood vessels to give a new blood supply - this is called neovascularisation. Unfortunately, the new vessels are very weak and grow on the surface of the retina and into the vitreous gel. The vessels can bleed easily, causing haemorrhages within the vitreous and scar tissue that can pull on the retina, leading to a retinal detachment. People are not usually aware of neovascularisation itself, but its consequences – bleeding or retinal detachment are serious and can lead to sudden and severe visual loss. Without treatment, proliferative diabetic retinopathy can lead to total loss of vision. |
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Neovascularisation at the optic nerve: Proliferative Diabetic Retinopathy
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Proliferative diabetic retinopathy can be controlled by laser treatment as long as it is diagnosed early enough. The laser treatment aims to destroy those areas of the retina that are damaged, reducing the need for the retina to produce new vessels. Laser treatment can only preserve sight; it cannot restore any vision that has already been lost.
Other ways in which diabetes can affect the eyes are:
- Temporary blurring – this is sometimes the first symptom of diabetes, and can also occur at times when the diabetes is poorly controlled. People notice variable vision and frequent changes in spectacle prescription. This is due to varying blood sugar levels and swelling of the lens.
- Cataract – Diabetics can develop cataract earlier than those who are not diabetic.
- Cranial nerve palsies – The muscles that move the eyes are controlled by nerves that originate in the brain. Diabetics are at increased risk of nerve palsies, where the nerves do not work and therefore the eyes do not move together in a coordinated way. This leads to a sudden onset of double vision when looking in a particular direction, depending on which nerve is affected. Most nerve palsies caused by diabetes are self resolving, but need investigation to rule out any more serious pathology.
- Blepharitis – This is more common in diabetics, together with an increased risk of corneal infection and a reduced corneal healing rate. Dry eye is also more common in those who are diabetic.
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