Sunday, December 9, 2007

4.3 Diabetic retina

Diabetes is a nasty disease of ischemia. There is no cure for it just yet. It comes in two forms, the familiar Type 1 and Type 2. There used to be an aging factor for Type 2 (i.e., adult-onset), now even children develop Type 2 diabetes. Long-term diabetes leads to many complications in the eye including diabetic retinopathy, cataracts (posted previously, see Section 2.2.3), and sometimes, neovascular glaucoma.

Let us ponder this wide-field retinal image first:

In the center, there is an island. Which is surrounded by a sea of bright spots. In the middle of the island, you can see the macula, to its left is the optic disc, and to its right, a suspiciously looking dark-red area. Also within each bright spot, there are black specks. Yes, this is a diabetic retina after a pan-retinal laser photo-coagulation (PLP) treatment. The bright spots are laser burns and within each spot, pigments from pigment epithelium. The purpose is to stop bleeding as that in the dark-red area. Usually there are 1,000 burns.

Why is this treatment necessary? Well, we need to backtrack a little. Because of the structural changes of the blood vessels in a diabetic retina (in the whole body, in fact), we can see micro-aneurysms (often known as background or non-proliferative diabetic retinopathy). Then three things happen: (1) the delivery of oxygen is inadequate; (2) the blood vessels sometimes leak; and (3) the macula may become edematous. These get progressively worse as time goes on. Eventually, the ischemia gets so bad, new blood vessels proliferate to provide more oxygen. So now we have the proliferative diabetic retinopathy. These abnormal vessels often break and blood will leak into the vitreous necessitating a vitrectomy (surgical removal of the vitreous). PLP is therefore performed to stop these hemorrhages. The image above may look terrible, yet the patient still retains central vision, even though peripheral vision is somewhat compromised. This is still far better than a total vision loss.

To avoid or delay these complications, tight blood sugar control is absolutely crucial. So if you are a diabetic, do yourself a big favor: Follow your diabetes doctor's instructions religiously. And pay attention to your Hb A1c level and monitor your own blood glucose closely.

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