Diabetic Retinopathy, Macular Oedema and Haemorrhages
Diabetic retinopathy is a leading cause of blindness. It occurs when diabetes damages the tiny blood vessels within the retina, the light-sensitive tissue within the eye that functions like the digital chip or film in a camera. A healthy retina is necessary for good visual acuity.
Diabetic retinopathy initially occurs in the less sensitive areas of the retina so that you may not be aware that you have sight-threatening changes. Over time, diabetic retinopathy progresses and causes vision loss. That is why regular screening is essential to detect damage before it is too late
Diabetes and retinal blood vessels
The blood vessels nourishing the retina are distributed throughout the retina 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).
Who is at risk of diabetic associated eye problems
Everyone with diabetes is at risk. This includes 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 diabetics will develop some diabetic retinopathy during their lifetime.
During pregnancy diabetic retinopathy may be more of a problem as altering hormones can cause diabetic retinal change. Often a review at each trimester is indicated.
You will always need a detailed retinal examination. This can only be performed with eye drops to dilate the pupil. These will probably blur your vision and increase glare for a few hours. We strongly suggest that you do not drive home after your assessment.
Ocular Coherence Tomography (OCT) will be performed as it is the most sensitive method to assess and monitor macular oedema. OCT takes a very short time and is not invasive.
A Fluorescein Angiogram may be required. This procedure is where a special dye is injected into the back of the hand. The eye is then photographed over a period of five minutes as the dye flows through the body.
Stages of Diabetic Retinopathy
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 – known as macular oedema.
Over time, the more peripheral blood vessels collapse and block resulting in areas of no blood flow. The lack of oxygen generates signals from the retina which trigger new blood vessels to grow. 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).
Complications of diabetic retinopathy
Fluid leaks into the centre of the macula (the part of the eye used for sharp, central vision) making 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. Haemorrhages severely affect vision. Vitreous 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.