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Glasses, Contact Lenses and Blood Sugar Levels

How daily highs or lows may affect your vision prescription

When I was diagnosed with type 1 diabetes at 22 years old, my life changed in a lot of ways. Most of them weren’t pleasant – like having to count carbs at every meal and permanently redefine my relationship with ice cream. But there was also one strange, if fleeting, positive: my vision temporarily improved.

I remember sitting in the library one afternoon shortly after being diagnosed. I noticed that, for the first time since first grade, I could see my fingers clearly when I held them at arm’s length. It was such a dramatic change that I had to get a new prescription for my contacts. Then, a month or so after I began to get my blood glucose levels into target range, my vision returned to its old, extremely nearsighted state. What happened?

Most people know that unmanaged blood sugar may lead to a diabetic eye disease, including retinopathy and glaucoma, which can damage vessels and nerves in the eye and may lead to serious complications. But it turns out that fluctuating blood sugar levels may also affect one’s vision when no long-term damage has occurred, and a person living with diabetes who wears glasses or contacts may find they need to have their vision prescription adjusted.

According to Lloyd P. Aiello, MD, professor of ophthalmology at Harvard Medical School and director of the Joslin Center’s Beetham Eye Institute, fluctuating blood glucose levels may cause the lens of the eye – that’s the part that focuses light rays so that one can see clearly – to swell. The level of swelling in the lens affects whether images are properly focused. According to Aiello, these swelling-induced changes can be mild or quite substantial, and are most evident at very high or low blood glucose, or when levels of blood glucose are changing rapidly.

A person who has experienced vision changes may wish to work with someone on their diabetes care team to get their blood glucose levels in target range and to minimize fluctuations. This may mean a prescription adjustment after managing blood glucose levels, but once a person is on track, their prescription shouldn’t continue to change.

In short, this is yet another reason for anyone living with diabetes – type 1 or type 2 – to have our eyes checked regularly, both to look for potential signs of long-term damage and to make sure we still have the proper prescription for our glasses or contacts. It’s also a near-term reminder of the importance of keeping blood glucose levels within target range.

I had a moment of sadness when my poor eyesight returned and the world once again became fuzzy around the edges. But any frustration quickly faded when I remembered that my bad eyesight actually reflects what a good job I’m doing of managing my blood sugar. I’m happy to say that it’s now been fourteen years since my diagnosis, and my prescription hasn’t changed since.

Catherine Price is a freelance journalist and type 1 diabetic who has written for The New York Times, Slate, Popular Science and O Magazine, among others. Her newest book, Vitamania: Our Obsessive Quest for Nutritional Perfection, is available from Penguin Press. She blogs about diabetes at ASweetLife.org and you can follow her on Twitter @Catherine_Price. Price is a paid contributor for The DX. All opinions contained in this article reflect those of the contributor and interviewee, and not of Sanofi US, its employees, agencies, or affiliates.

© 2015 The DX: The Diabetes Experience

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