Diabetic Blindness - Retinopathy

Retinopathy means "sick retina" and it is among the most terrifying of diabetic complications. What happens in retinopathy is that because of the 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.

These diabetic blood vessels have weak walls unlike healthy vessels, and eventually they burst, releasing blood into the eye. 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 this kind of macular edema which is a major reason they are probably the last drug anyone with diabetes should take.

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 even 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 pre-diabetes, so just getting your blood sugars to the mediocre levels most doctors suggest for people with diabetes (well within the pre-diabetic range) is not enough.


DPPT Data and Pre-Diabetic Retinopathy

Getting Better Control Occasionally Temporarily Worsens Retinopathy

Sadly, it turns out that if you have been running very high blood sugars for a while, 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 DCCT 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 having high blood sugars, NOT 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 also no evidence that lowering blood sugars more slowly avoids this kind of worsening.

Here's a review of the research on this subject that makes all this clear:

Diabetic Retinopathy
Donald S. Fong, MD, MPH1, Lloyd P. Aiello, MD, PHD, Frederick L. Ferris, III, MD and Ronald Klein, MD

Diabetes Care 27:2540-2553, 2004
http://care.diabetesjournals.org/cgi/content/full/27/10/2540


"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 for sure, as troublesome as temporary worsening might be, if you don't lower your blood sugar, the end results for your vision is much, much worse.

Blurry Vision is NOT a Sign of Retinopathy!

On diagnosis many people with Type 2 will 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 is caused because changing blood sugar concentrations change the concentration of sugar in your lens and the fluids of your eye, which change your vision, especially if you are old enough to need bifocals.

Of course, over time those high blood sugars, if not lowered, will result in retinopathy, but they are not a symptom of permanent damage. Sadly, there are no warning symptoms of the kind of retinopathy that causes blindness until you start experiencing eye bleeds.

If you experience this kind of vision change with blood sugar changes, be sure to measure your blood sugar before you get the optometrist to prescribe lenses for you and make sure it 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 until they've spent a few months lowering their blood sugars to normal ranges because glasses prescribed when they are running high will no longer correct their vision properly.