Diabetic Blindness - Retinopathy

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Diabetic Blindness - Retinopathy

Retinopathy means "sick retina" and it is among the most terrifying of diabetic complications. What happens in retinopathy is that, with continual exposure to high blood sugars, tiny blood vessels start to grow in a disordered and out of control fashion in the retina--the part of the eye where nerves transmit light images to the brain.

Unlike healthy vessels, these diabetic blood vessels have weak walls, and eventually they burst, releasing blood into the eye. Not only that, but if they are left untreated, these overgrown vessels eventually destroy the retina's ability to transmit images to the brain, resulting in permanent blindness.

There are various terms doctors use to refer to retinopathy. One is "proliferative retinopathy" referring to the way that the tiny blood vessels proliferate. Another is "macular edema" referring to swelling in the part of the retina that gives us central vision. Actos and Avandia have been found to cause an increase in macular edema which is a major reason they are probably the last drug anyone with diabetes should be taking.

Doctors currently treat retinopathy by using lasers to zap shut bleeding or swollen blood vessels in the eye. This helps retain vision, though it cannot restore vision that has been lost. Over time if blood sugars continue to be high--200 mg/dl (11 mmol/l) or more-- vision will deteriorate despite with this treatment.

The only way to reverse retinopathy is to get blood sugars down to truly normal levels--not the levels flagged as "good for diabetics" but normal levels. That is because recent research has found retinopathic changes happening in the eyes of 1 out of ever 12 people diagnosed with prediabetes, so just getting your blood sugars to the mediocre levels most doctors suggest for people with diabetes (well within the prediabetic range) is not enough.

DPPT Data and Pre-Diabetic Retinopathy

You can read more about the evidence that links retinopathy with prediabetic blood sugar levels here: Research Connecting Blood Sugar Level with Organ Damage

You can learn how to bring your blood sugar down to a safe level here: How to Get Your Blood Sugar Under Control

Getting Better Control Occasionally Will Temporarily Worsen Retinopathy

If you have been running very high blood sugars for a long time, lowering your blood sugars may initially make retinopathy worse, not better. But this does not mean it isn't worth doing. Over time, many studies including the landmark DCCT study have found that those people who experienced worsened retinopathy after lowering their blood sugars ended up with better vision years later than those who did not lower their blood sugar.The damage is done by things that occur while you have the very high high blood sugars and chemicals that develop in your eye in response to these high sugars, it is not caused by correcting them.

This worsening, which is fairly rare, almost always happens to people who are using insulin to lower blood sugar, not diet.

There is no evidence that lowering blood sugars more slowly avoids this kind of worsening.

Here's an excellent review that discusses the published research on this subject:

Diabetic Retinopathy Donald S. Fong, MD, et al. Diabetes Care 27:2540-2553, 2004

From that article:
Patients who developed early worsening as a result of the intensive treatment were similar to or had more favorable outcomes than those in the conventional group who did not have early worsening. Analysis did not suggest reduction of early worsening with more gradual reduction of glycemia.
One thing is certain, as troublesome as temporary worsening might be, if you don't lower your blood sugar, the end results for your vision will much, much worse.

Blurry Vision is NOT a Sign of Retinopathy

On diagnosis many people with Type 2 diabetes report that they have long had problems with blurry vision that comes and goes. When they lower their blood sugar, many will suddenly find that their glasses seem to have stopped working, too.

This kind of visual problem is not caused by retinopathy. It happens because changing blood sugar concentrations change the concentration of sugar in your lens and in the fluids of your eye and this changes your vision, just as if you had changed an eyeglass prescription. This sensitivity to high blood sugars is especially noticeable when you are old enough to need bifocals.

There are no warning symptoms of the kind of retinopathy that causes blindness until you start experiencing eye bleeds, though an ophthalmologist can see early signs of abnormal blood vessel growth in your retina long before the vessels rupture. This is why if you are diagnosed with diabetes you should see an ophthalmologist, not an optometrist, every year for a full dilated eye exam.

If you experience vision changes with blood sugar changes, be sure to measure your blood sugar before you get the optometrist to prescribe lenses for you and make sure your blood sugar is in your target range so that your glasses will continue to work well. Many people have found it a good idea NOT to get new glasses right after a diabetes diagnosis. Wait until you've lowered their blood sugars to the normal range because glasses prescribed when blood sugars are high are running high will no longer correct vision properly when you have lowered your blood sugar.
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