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Diabetes Mellitus and the Eye

What is diabetes mellitus?

Diabetes mellitusDiabetes mellitus, or simply diabetes, is a group of metabolic diseases in which the ability to process glucose is impaired. If left untreated, diabetes can cause a host of long-term complications, including damage to the retina. manifests when the pancreas secretes insufficient amounts of insulin, or if the body loses its ability to process insulin properly.  Insulin is responsible for the regulation of blood sugar levels.  It may occur during childhood, but usually arise later in life.

Types of Diabetes:

  1. Type 1 (insulin dependant).
    • Occurs at a younger age.
    • Insufficient or no insulin production.
    • Controlled by insulin injections.
  2. Type 2 (non-insulin dependant).
    • Occurs later in life.
    • Insulin is produced, but in insufficient quantities.
    • Produced insulin is not utilized properly by the body.
    • Controlled by diet and medication (injections only in rare cases).
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Diabetes and the Eye

If diabetes is not well controlled, it may cause vision loss.  It is important for diabetics to have an eye examination at least every second year, or as instructed by their doctor.

Diabetes affects the eyes in many ways.  As the blood sugar levels fluctuate, it causes a fluctuation in vision.  Diabetes may also cause cataractA cataract forms when the natural lens in the eye is, or is starting to become, opaque. If not treated, it can lead to blindness, which in most cases can be treated. See Cataract Centre – Understanding Cataracts. formation.  The blood vessels and the retinaThe retina is the receptor of light at the back of the eye. It fulfils the same function as the film in a film camera or the image sensor in a digital camera. The retina translates the images into electrical signals that are sent via the optic nerve to the visual cortex in the brain, where it is interpreted as the images we see. See Info on Eyes – Anatomy. are the most important structures to monitor.  If Diabetes affects the retina it is known as Diabetic Retinopathy (DR), which is classified into different stages:

  1. Background Diabetic Retinopathy.
    • These patients may present with normal vision.
    • Microaneurysms (Microscopic ‘budding’ of blood vessels in the retina).
    • Haemorrhages (Leakage of blood from blood vessels).
    • Exudates (Leakage of fluid from blood vessels).
    • Swelling of the retina (caused by leakage of fluids).
  2. Preproliferative Diabetic Retinopathy.
    • Cotton wool spots (Build-up of cellular material because of a lack of blood flow in a certain area, which is responsible for the white appearance of lesions).
    • Intraretinal microvascular abnormalities (growth of fine blood vessels, which runs between arteries and veins).
    • Dilation, looping and segmentation of veins.
    • Narrowing and silver wiring of arteries.
    • Dark blot haemorrhages (bleeding) in the retina.
  3. Macular oedema.
    • As Background Diabetic Retinopathy becomes more severe, the macula becomes involved and swells.
    • Decrease in central vision.
    • Difficulty recognizing peoples faces.
    • Difficulty reading.
  4. Proliferative Diabetic Retinopathy.
    • Blood vessels in the retina becomes blocked.
    • Neovascularization (growth of new blood vessels, which are weaker than normal vessels, which grow onto the retina, optic nerveThe optic nerve transmits the visual signals from the retina to the visual cortex in the brain, where it is interpreted as the images we see. See Info on Eyes – Anatomy. and the iris).
    • Bleeding into the vitreous of the eye.
    • Scar tissue formation on the retina, which may lead to a retinal detachment.

What are the eye tests done for diabetic retinopathy?

The pupils are dilated with special drops, and a comprehensive examination of the retina at the back of the eye is done.  The vision will also be documented, to ensure no substantial decrease in vision occurred since the last follow-up visit.  In some cases a Fluorescein angiography (FA) is necessary to determine whether there is growth of new blood vessels or the development of avascular areas.  During a FA, a special dye is injected into the blood stream.  A series of special photographs are then taken of the retina to determine the above.  The retina may also be monitored by OCT (Optical Coherence Tomography) measurement of the retina, which may show thickening and thus swelling of the retina.

Management

Background Diabetic Retinopathy

  • No treatment required.
  • Annual check up .

Preproliferative Diabetic Retinopathy

  • Very close monitoring to prevent the onset of Proliferative DR.
  • Photocoagulation in selected cases where the vision in the other eye is lost due to Proliferative DR.

Macular oedema

  • Argon laser photocoagulation.
  • Regular follow-ups.

Proliferative Diabetic Retinpoathy

  • Panretinal laser photocoagulation to destroy new blood vessels in order to prevent haemorrhages and retinal detachment.
  • Regular follow-ups.

These treatments can only preserve the sight you still have, and will not restore the sight that was lost.  The best way to preserve your sight is to control blood sugar levels and prevent the complications of diabetes.