When Shouldn't Patients with Diabetes Get Glasses?

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.


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

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  • Toan Tran
    Posted at 11:27h, 12 September Reply

    Love the blogs! Good reminders and reviews for the eye docs as well as patiet education.

  • Char Retkowski
    Posted at 16:13h, 27 July Reply

    I am currently 1 of “those diabetics” that cannot get the glasses to work. I am on my 2nd “redone” pair of lenses. My problem is that my glucose have been better than they have been in years (100-128 am fasting). We had thought it was that I wasn’t adjusting to progressive lenses. Now I’m finding differently. The problem is I need glasses. So, what do I do? And telling me to get control of glucose isn’t the “fix”.

    • Randall Wong, M.D.
      Posted at 17:55h, 20 August Reply

      Just wondering if your sugar was stable (i.e. consistent, albeit consistently high or low) for the previous 2-3 weeks before refraction. You could also have cataracts or diabetic macular edema. Any of these possible?


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