What is Diabetic Retinopathy?
Diabetic retinopathy is a leading cause of blindness in working-age Australians. It occurs when diabetes damages the tiny blood vessels within the retina, the light-sensitive tissue within the eye that functions like film in a camera. A healthy retina is necessary for good visual acuity.
Diabetic retinopathy initially develops in the less sensitive areas of the retina, so patients may be unaware of the sight-threatening changes. Over time, the condition progresses causing vision loss and more advanced stages of the disease can result in sight-threatening changes. Regular eye examinations are essential to detect early changes or progression.
Blood vessels nourishing the retina are distributed throughout the area like a garden dripper system from a central tap. The elevated blood sugar from diabetes acts like an acid that etches into the lining of the pipe-like blood vessels. This corrosion gradually damages the blood vessels so that they either become porous and leak excess fluid (called macular oedema) or the walls collapse resulting in areas of no blood flow (particularly at the extremes of the system).
Everyone with diabetes is at risk of diabetic associated eye conditions, including people with Type 1 and Type 2 Diabetes. The longer the duration of diabetes, the more likely diabetic retinopathy will develop. Nearly half of all people with diabetes will develop some diabetic retinopathy during their lifetime.
During pregnancy diabetic retinopathy may be more of a problem as hormones can cause diabetic retinal change. Often a review at each trimester is recommended.
A detailed retinal examination must be performed after dilating the pupil with eye drops. These drops will blur your vision and increase glare for a few hours. You are strongly discouraged from driving home after the assessment.
Ocular Coherence Tomography (OCT) will be performed as it is the most sensitive method to assess and monitor macular oedema. It does not take long to acquire the OCT images, and it is non-invasive.
A Fluorescein Angiogram may be indicated in some patients. Fluorescein angiograms have been performed for over 30 years and is proven to be safe and well tolerated. The procedure involves injecting fluorescein dye into a vein in the back of the hand or in the bend of the elbow joint. Once the dye is injected, a series of photos are acquired to document the dye circulating inside the eye, for a period of 5-10 minutes.
At this earliest stage, microaneurysms (small balloon-like distensions of the weakened/corroded blood vessels) occur. These porous vessels allow excess fluid to escape into the retina – this is known as macular oedema.
Over time, the more peripheral blood vessels in the retina collapse resulting in areas of no blood flow. The lack of oxygen to these areas generates signals from the retina to trigger new blood vessel growth. This condition is called proliferative retinopathy. Unfortunately, these new blood vessels are abnormal and fragile, and they extend into the inner eye cavity (the vitreous) rather than into the retina itself).
Fluid leaks into the centre of the macula (the part of the eye used for sharp, central vision) causing the macula swell and blurring vision. Macular oedema can occur at any stage of diabetic retinopathy although it is more likely to occur as the disease progresses. About half of the people with proliferative retinopathy also have macular oedema.
The fragile new vessels of proliferative disease have a high risk of rupture which causes bleeding (haemorrhage) into the vitreous and severely affect vision. The haemorrhages often dissipate with time but sometimes an operation called ‘vitrectomy’ is needed to clear out the blood and restore clear vision. Haemorrhages tend to happen more than once.