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February 13, 2006

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Question from Staten Island, New York, USA:

My 14 year old son, who has had type 1 diabetes since he was one year old, recently went to his eye doctor. He was complaining he couldn't see the board at school. The doctor did all the tests and said that my son was borderline for needing glasses and that we'd have to monitor the situation. Six months later, I took him to the mall and we had his eyes tested again but, because his blood sugar was 238 mg/dl [13.2 mmol/L], he wouldn't write him a prescription for glasses. He told us to come back the following week when his blood sugar was within range. They couldn't do the glaucoma test on him because he couldn't let them do the puff in his eye part at that time. So, we waited four months and went to another eye doctor at the mall. I waited for his blood sugar to come down low enough, 118 mg/dl [6.6 mmol/L], to take all the tests. He wrote him a prescription for glasses. He has glasses now and he's happy now seeing the board at school. The problem is, on the last visit, the doctor found that he had the beginnings of glaucoma, 21+22 on the ticker tape, even with his blood sugar at 118 mg/dl [6.6 mmol/L]. I took him to another eye doctor and he told me that my son's blood sugars had to be under 150 mg/dl [8.3 mmol/L] for a month with no sugars over that, not even once, to get a true reading for glaucoma! I told him that ain't happening, not in my lifetime. It's hard to regulate a kid's sugars. They fluctuate so much, but his A1c levels are 7.4 to 9.0 depending on what time of year it is. If he's in school and it's wintertime, his A1cs are high. Summertime, outside playing he's a lot lower. I spoke to my son's endocrinologist about all this and he said that he's too young to have this problem, even though he's diabetic for so long. He told me walk, don't run to the eye doctor and let me know what he says. I did. But, is it because his sugars aren't under 150 mg/dl [8.3 mmol/L], does he have the beginnings of glaucoma or does he really have it cause of built up pressure behind his eyes? I am confused with all of this.

Answer:

There is no evidence that blood sugar level affects intraocular pressure (internal eye pressure). Blood sugar levels can dramatically effect the eyeglass prescription, however. These are two completely separate issues.

Glaucoma is defined as “progressive damage to the optic nerve with characteristic visual field abnormalities, usually but not always associated with elevated intraocular pressure.” Most people with an eye pressure of under 25mm do not have glaucoma, and it is rare in kids, though it can happen. Eye pressure is only one of several factors that determine whether or not a patient has glaucoma; the others are the size and shape of the optic nerve at the back of the eye and the visual field (in lay terms, the quality of peripheral vision). People with diabetes are about 50% more likely to have glaucoma but, again, it is quite uncommon in teenagers unless there is severe retinopathy leading to what is called “neovascular glaucoma.” Family history of juvenile glaucoma, African-American ancestry and thin corneas also elevate the risk. Eye pressure is the most emphasized but one of the least important factors in determining whether or not a patient has glaucoma.

I would recommend that your son have multiple measurements of his intraocular pressure, a threshold visual field examination, stereo optic nerve photos and a measurement of corneal thickness (most “mall doctors” don’t have all these tests, which is why I would never bring a family member with diabetes to the mall for an eye exam. You get what you pay for which, in this case, may have been a whole lot of confusion and needless worry.) If in doubt, see a glaucoma specialist.

The risk of serious eye disease, and all other diabetes complications, goes up with increasing A1c levels, particularly diabetic retinopathy. Your son’s goal should be an A1c less than 7.0%, ideally, less than 6.5% on a consistent basis. I know this is difficult. Work with his endocrinologist, see a diabetes educator and consider using an insulin pump to make it so.

PC