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A1C Now Used to Diagnose Diabetes

The American Diabetes Association now recommends basing the diagnosis of diabetes upon the hemoglobin A1C levels and not on fasting glucose tests.  In addition, an A1C of less than 7.0% should be the target for glucose control.  How with this impact the treatment of diabetic retinopathy?

The change in recommendations stems from the fact that the A1C blood test is an easier, and faster, test to run than measuring a fasting plasma glucose and an oral glucose tolerance test.  Both tests require overnight fasting for accuracy; that is, it relies on patient compliance.  The A1C does NOT require overnight fasting.

A1C measures the average blood glucose levels for the period of up to 3 months and was previously used just to measure sugar control over time, but now, it is recommended to be used for diagnosis;

  • A1C  of 5%  – no disease
  • A1C of 5.7 to 6.4% – likely prediabetes
  • A1C > 6.5% – likely diabetes

The ability to diagnose the test using A1C guidelines now means that the diagnosis of diabetes can be made earlier.  Earlier detection (diagnosis) may mean a greater chance of  “curing” type II diabetes by making lifestyle changes earlier.

What Does This Mean? The ability to diagnose and treat this disease now has some firm, “black and white,” guidelines.  More patients will be detected and at an earlier age.  Therapy and education may be instituted earlier.  For instance, patient education regarding diabetic retinopathy may be instituted sooner.  In this respect, more patients will be “saved” over the long run.  In theory, patients will be directed for eye exams before the retinopathy begins.

It is also likely, that with tighter sugar control (i.e. good A1C levels), diabetic eye disease will progress slower.  We’ll see.

“Randy”

Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist
Fairfax Virginia

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Diabetes – A Disease of Blood Vessels, Especially in the Eye

Did you ever hear that diabetes is a disease of blood vessels?  Most people think that the definition of diabetes is simply uncontrolled blood sugar, but, in reality, diabetes may be thought of as a vascular disease.

Diabetes can be a very nasty disease affecting most organs in the body.  Common problems caused by diabetes include peripheral neuropathy, kidney failure and diabetic retinopathy.  The common denominator?  Bad blood vessels.

Patients with diabetes can develop peripheral neuropathy. Symptoms of  peripheral neuropathy include “pain,” but also numbness of the extremities.  Numbness usually begins at the toes and ascends up the legs.  At some point the fingers, hands and arms may become involved.  The upper extremities (hands and arms) become involved when the numbness has reached a high enough point on the leg so it is now about same distance from the heart as the finger tips.  Basically, just remember, when caused by diabetes, peripheral neuropathy begins in the feet.

The problem?  The fine, small caliber blood vessels that feed the nerves at the ends of the toes and fingers that give us sensation, eventually fail.  Loss of blood supply leads to loss of nerve endings that cause numbness.

Diabetes causes diabetic nephropathy in the kidneys. Here, the fine microvasculature (thin, tiny blood vessels) start to become incompetent and the small filters in the kidney, glomeruli, are unable to properly filter blood and “spill” protein into the urine.  Normally, protein, which are rather large molecules, is retained in the blood stream after filtration through the glomeruli in the kidney.  Due to damage caused by diabetes, these vascular filters do not work properly, letting protein accumulate in the urine.  Long-standing diabetic nephropathy can lead to renal (kidney) failure.  Again, small, fine blood vessels are the culprit.

Diabetic retinopathy is a vascular problem as well. As we know, the most common problem in patients with diabetic retinopathy is diabetic macular edema.  Macular edema develops when the small retinal blood vessels also “leak” into the surrounding tissue.  This can cause decreased vision if it occurs within the macula.  The tiny blood vessels become incompetent and start to leak fluid and proteins into the retinal space.  Sound familiar?

Diabetic retinopathy can also cause loss of blood supple to the retina.  When a tissue has reduced blood supply, or, when a tissue does not receive the proper amount of oxygen (via the blood), the condition is called ischemia.  Ischemia arises in the retina when the fine microvasculature of the retina stops to function.  It no longer gets sufficient oxygen to the retinal cells.  This ischemia is not treatable, can cause loss of vision if it affects the macula and may lead to proliferative diabetic retinopathy.

Researchers have focused attention on pericytes, cells that line the blood vessel walls, as the principal culprit in these “vascular” diseases.  Long term exposure to “high sugar” may be related, but indirectly.  Clearly, diabetes is associated with damage to the fine microvascular in the body.  Whether there is a direct cause-effect relationship between sugar and damage, we have yet to know.  Most likely, diabetes causes a cascade of events that can cause, over time, damage to the peripheral nerves, kidney and eyes.

“Randy”

Randall V. Wong, M.D.
www.TotalRetina.com
Ophthalmologist, Retina Specialist

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When Shouldn't Patients with Diabetes Get Glasses?

Patients with diabetes need to be careful when getting new glasses.  Patients with diabetes should NOT get glasses when their blood sugar is abnormally high or low.

Believe it or not, several times a year, I will see a patient that is referred for unexplained decrease in vision, OR, I will have a patient that keeps getting the “wrong” glasses.  The patient goes in for an exam, doctor writes prescription, but 2 weeks later when the glasses come in…………they don’t work.  Similarly, I also see patients that complain of decreased vision after being diagnosed with diabetes.  What’s going on?

Let’s “examine” the patient that has unexplained decreased vision. I will ask some preliminary questions, usually involving health, bathroom habits at night (see post on early signs of diabetes), thirst, weight loss or weight gain, etc.  The undiagnosed diabetic will tell me that there is constant thirst, sleep is interrupted every night for a bathroom (pee) break and there has been weight loss.  This has been going on for months, and now, the vision is horrible.  The eye exam is usually normal; no cataract and no diabetic retinopathy.

Now, let’s talk about the patient who can’t get glasses that work. I will ask the same preliminary questions, suspecting diabetes.  The eye exam is usually also normal.  I will refer the patient back to their primary care physician and ask for a diabetic workup.

Last, the patient who has been recently diagnosed with diabetes and cannot see.  Guess what?  Normal eye exam, too.

In all cases, the blood sugar is abnormal (either high or low).  At this time, I would recommend reading my post on early signs of diabetes.

The case of “unexplained decrease in vision.” This is the typical case of an undiagnosed diabetic.  High blood sugar levels cause the excessive thirst, night time potty breaks and the blurred vision.  As I explain in a previous post, sugar draws water out of our tissues and also into the eye’s lens.  These are common symptoms of undiagnosed diabetes.  Correction of blood sugar should rectify the symptoms in a matter of weeks.  With regard to the glasses, the patient should wait several weeks AFTER treatment has been initiated and the blood sugar has returned to normal before getting new glasses/contacts.

The case of the patient who can’t get glasses that work.  Same rationale as above.  The sugar is probably uncontrolled and too high when initially getting glasses.  Sugar enters the lens, gets changed to sorbitol, water enters the lens and alters the overall eye prescription.  Basically, the sugar level has changed dramatically between eye exam and glasses pickup, thus, the prescription has changed.  Here, as above, wait until sugar has returned to normal for a few weeks, get RE-EXAMINED and obtain new glasses.

The last case of the patient recently diagnosed with diabetes and cannot see. Here, the sugar has been uncontrolled (undiagnosed diabetic) for months or longer.  The patient becomes used to a certain level of vision.  Diabetes is diagnosed and sugar becomes controlled.  The water content of the lens changes with controlled sugar, and……………………..vision gets blurry.  Probably, all along, the patient needed glasses anyway, was mislead by the sugar/water problem in the lens, and now gets blurry (as he always should have been) with better sugar control.  Again, wait a few weeks with normal sugars and then get glasses.

I recommend read this article for more early signs of diabetes.

“Randy”

Randall V. Wong, M.D.
www.TotalRetina.com
Ophthalmologist, Retina Specialist

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Thirst, Frequency and Blurry Vision……Early Signs of Diabetes?

Excessive thirst, increased urinary frequency and blurry vision can all be early signs of undetected diabetes mellitus.

What you already know.  Diabetes mellitus is the body’s inability to decrease the sugar in the blood.  This “serum glucose” rises after every meal as our food is broken down into its basic components.  In the normal situation, a rise in blood sugar causes insulin to be secreted into the blood stream.  Insulin takes blood sugar out of the blood and delivers it to our tissues.  As a result, serum glucose levels are kept low and maintained at a steady state.  If  insufficient insulin or no insulin is produced, then the sugar remains in the blood stream and the sugar level rises.

High levels of sugar increase the “osmolarity” of the blood.  Osmolarity is a difficult term to understand, but it reflects the ability of a substance to attract water.  The higher the osmolarity of a liquid, the more water it will attract and retain.  In this case, as the serum glucose increases, it will literally draw water out of our tissues.  We feel thirsty because our tissues are actually dehydrated, hence the increased thirst.  The increased water in our blood then causes more urination.

What causes the blurry vision? Again, it is the high sugar and osmolarity, but with a slight twist.  The high sugar leaks into the eye and then gets absorbed by the natural lens.  The sugar, or glucose, is then changed to sorbitol, another form of sugar.  The sorbitol does not leave the lens very readily and is basically trapped.  Sorbitol, like glucose, also adds to osmolarity.  So, the sorbitol attracts water and causes the lens to swell.  This causes the vision to blur.  Even with correction of sugar, it may take weeks for the lens to return to its more normal state.

Usually, these are the first, early signs of diabetes.  The vision changes are usually not due to diabetic retinopathy at this time as this takes years to develop.

In the end, all three symptoms are based on the same mechanism.  Once the abnormality is identified and sugar returns to normal using either diet, oral agents or insulin, water redistributes normally, our tissues rehydrate and the eye returns to normal.  Vision, too, should return nicely.

“Randy”

Randall V. Wong, M.D.
www.TotalRetina.com
Ophthalmologist, Retina Specialist

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