Eye disease in Diabetes mellitus

Diabetes mellitus can affect the eye in many ways. Cataracts and glaucoma are more common in patients with diabetes mellitus. In addition, it can affect the part of the eye at the back which is responsible for sensing light and colour, the retina. In the retina, small vessels become "leaky" resulting in the formation of exudates, which are the yellow areas seen in the picture below. If these exudates are too close to the most sensitive area of the retina, the macula, this can impair your vision.

Diabetes mellitus also causes weakness in the blood vessel walls causing them to bulge and form microaneurysms. Generally, all persons with diabetes mellitus develop some of these microaneurysms or exudates if they have diabetes for a sufficient length of time. Unless the exudates are very close to the macula, they and the microaneuryms are harmless and will not impair your vision. We call this "background retinopathy." In fact, almost all persons who have diabetes mellitus for 20 years have changes that are due to background retinopathy.

Patients who have diabetes mellitus can also develop "proliferative retinopathy". In these cases, new blood vessels grow on the retina. These new blood vessels are fragile and can bleed giving rise to haemorrhage in the eye and this can lead to blindness.

 It is important to pick up the changes due to maculopathy and proliferative retinopathy early as laser therapy can reduce the likelihood of loss of vision. In order to make sure that this is carried out at the right time, you need to go for regular eye screening. It is recommended that you have your eyes screened when you first find out you have type 2 diabetes mellitus. If they are normal, you should continue to have screening once a year. If there are any abnormalities that require attention, your doctor will refer you to an ophthalmologist (eye specialist) for treatment. Patients with type 1 diabetes mellitus do not require eye screening until 3 years after the diagnosis has been made and then once a year thereafter.

Screening can take 2 forms. Many centres can carry out fundal photography where a photograph is taken of the back of you eye allowing a doctor to look for any changes on the retina. The photograph will serve as a permanent record. In Singapore, the polyclinics have this service available. Contact your nearest polyclinic to find out when they have this service available as there are 2 cameras that move to various polyclinics at various times of the year. When a fundal camera is not available, your doctor can look at the retina directly using an instrument called an ophthalmoscope. Most doctors who manage diabetes will have an ophthalmoscope that can be used to examine the eyes carefully. Remember that your doctor has many patients to look after and make it a point to remind him or her of the time to examine your eyes.

Diabetic eye disease is one of the reasons we must try to keep the blood sugar under strict control, the DCCT has shown us that good control of blood sugar results in less eye disease and even if you already have eye disease, it can prevent it from getting worse.

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