Diabetic Eye Disease | Dr Amy Cohn

Diabetic retinopathy

It is estimated that 1.7 million Australians are affected by diabetes and this number is projected to increase significantly in the coming years. Diabetes affects blood vessels in the entire body. In the eyes this causes diabetic retinopathy. Diabetic retinopathy presents in many ways including macular oedema and neo-vascularisation (new blood vessels).

The chance of having diabetic retinopathy depends on how good your sugar control is and how long you have had it. Other factors like high blood pressure and smoking can increase the risk of diabetic damage to your retina.

Type I diabetics often do not have any retinopathy at the time that the diabetes is diagnosed. The incidence of diabetic retinopathy increases so that up to 90% of Type 1 diabetics have some changes after 30 years. The severity of this varies.

Type II diabetics can have some evidence of diabetic retinopathy in approximately 20% of cases at the time of diagnosis of the disease.

Irrespective of the type of diabetes you have, good control minimises the risk of vision loss.

Types of Diabetic Retinopathy

Diabetic retinopathy causes 5% of blindness world-wide. There are three main ways diabetes causes visual loss.

The first is macular oedema. The macular is the centre of the retina responsible for fine visual tasks such as reading, writing, driving and face recognition. In diabetic macular oedema, the blood vessels to this part of the retina become damaged by high sugar levels. This causes them to leak fluid and proteins (known as exudate) into the macular resulting in loss of vision.
The second is macular ischaemia. This is where the blood supply to the macular is permanently damaged. There is no cure for this.
The third is neo-vascularisation (or new blood vessel growth). This is known as ‘proliferative diabetic retinopathy’. Continued high blood sugar damages the blood vessels so the body attempts to compensate by growing new ones. These new vessels are not structurally normal. The cause vision loss by either bleeding (called a vitreous haemorrhage) or pulling the retina off the back wall of the eye (known as a traction retinal detachment).

Preventing Diabetic Retinopathy

The most important way to prevent development of diabetic retinopathy and visual loss is to control your sugar.

Other risk factors for progression include uncontrolled blood pressure and cholesterol, smoking and pregnancy (in some cases).

Treatment of Diabetic Retinopathy

Treatment of diabetic retinopathy depends on the type of retinopathy and the severity.

Macular oedema: Traditionally diabetic macular oedema has been treated with laser. In the last 20 years this has largely been replaced with intravitreal injections. This is where either an anti-vascular endothelial growth factor (anti-VEGF) or steroid is injected into the back of the eye. This is done in the doctor’s rooms and is generally well tolerated. There are many different types of anti-VEGF injections and Dr Cohn can discuss which one is right for you.

The injections often need to be repeated every 4- 20 weeks to maintain this improvement. After a certain period if the oedema is stable the anti-VEGF injections may be able to be ceased.

Steroid injections can also be injected into the eye to treat macula oedema. These are often used as a second line option if anti-VEGF agents have not worked well.

New vessels (neovascularisation): If new vessels are seen either on the front of the eye (iris) or the retina during an eye examination retinal laser will need to be performed urgently to prevent loss of vision and a painful type of glaucoma called neovascular glaucoma. Patients often do not know they have new vessels.

The laser is known as pan-retinal photocoagulation and is performed over 2-4 sittings. The eye is anaesthetised with drops and a contact lens is placed on the eye to view the retina. Multiple laser spots are put onto the retina to cause regression of the new vessels. Occasionally patients with new vessels may also be treated with intravitreal anti-VEGF injections.

Vitreous haemorrhage: If the new vessels rupture, blood accumulates in the space at the back of the eye known as the vitreous cavity. This is a vitreous haemorrhage. Patients often will present with ‘floaters’ or loss of vision. Management of this depends on the severity of the bleed. If there is a small bleed and there is a good view of the retina, laser can be safely performed, and the body resorbs the blood in time.

If there is a large bleed and there is a concern there are active new blood vessels obscured by the haemorrhage, surgery may be considered to remove the blood and perform laser at the same time. This is known as a vitrectomy. Dr Cohn will advise you as to the best course of action.

Traction Retinal Detachment: If the new blood vessels are pulling on the retina it may be necessary to perform a vitrectomy to remove them and any surrounding scar tissue.