Blood sugar control and vision changes

I’m wondering if anyone has experienced changes in vision with varying levels of control. I never needed glasses until about 6-7 years ago, when I started to become near-sighted. My A1Cs had been getting worse around this time and approaching 7 (they had been consistently around 6 since the time I was diagnosed until about a year or 2 before needing glasses - I think I was honeymooning for a few years and got away with just bolusing and eating almost anything). I didn’t think this was the cause though as every year the eye doctor told me I had no signs of diabetic eye damage and that my vision was probably just changing as I was getting older. Every year my prescription would get stronger. Late last year I made many changes including getting a CGM and lowering my A1C significantly, and started to notice my glasses were too strong for me. I went to the eye doc today and my prescription was cut in half! Has anyone else experienced anything like this?

It is common for vision to change as blood sugar rises or falls. Generally, it is more or less blurry and it can impact a prescription for glasses. Actually, this has happened to me a few times when I was in less tight control. However, usually, this happens as blood sugar changes rapidly. When my blood sugar was very high I had few issues, and when it is in the proper range I have few issues. It is the change that creates the issue.

As high blood sugar makes my eyesight more blurry, I find that it might take several days to stabilize.

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I was having my eyesight checked for new glasses when the opthalmologist asked if I was high. Well, I hadn’t checked but may have been as I was a bit early and had popped into a cafe for a coffee. I have been careful not to do this since as having high bgs obviously affects eyesight.

BG definitely affects vision. High BG causes myopia. I’m type 2 Dx’d with BGs in 300s fasting and even higher after meals. I’d been getting increasingly myopic for some time, but no one asked about the possibility of diabetes. After Dx, when I was getting BGs down, I then started getting hyperopic (farsighted). I couldn’t see someone across from me at the dining table, but I could see sharply at a distance.

Then gradually my eyesight returned to what it had been, slightly myopic.

These changes took about 2 weeks, so people are warned not to get new glasses during this period. I taped old lenses on top of my regular glasses during this period. Looked odd, but at least I could see.

Vision still changed in short term if BG got high, so I was happy when I got cataracts and fake lenses that didn’t change with BG changes.

The diabetic eye damage your doctor said you don’t have is retinopathy, damage to the retina, and it’s not reversible.

The changes in refraction I mentioned are different, and are reversible with good control.

“Blurry vision” is sort of imprecise, as vision changes with BG changes can make vision at one distance blurry but vision at another distance clearer.

When I went on my first pump, in 1980, my BG dropped into normal range so quickly that for a few days I felt ill – “normal” being so rare for my body that it felt odd. I already wore glasses, but within a day my vision became so sharp, it was like getting glasses for the first time.

Nowadays I notice the changes are more hourly. Before CGM, I could tell if I was high if (a) I was really really really thirsty, and (b) my vision was blurry (versus just being really thirsty because of eating too much salt). High BG alters the shape of the lens. I learned long ago to slightly increase my dose before getting my eyes tested so I wouldn’t be high.

With low BG, the theory is that the vision is less sharp because the brain, running low on energy, has trouble focusing on what your eyes are seeing. Hypoglycemic non-diabetics may also experience blurred vision. And chronic hypoglycemia apparently can kill retinal cells, affecting vision long-term (and making forced lows a poor tactic for reducing A1c).

Yup. I get blurry when high, and when it hits below 75 or so I get tunnel vision and cant focus. I usually get new glasses every year, and ALWAYS make sure my BG’s have been stable for at least a few days before going for appt.

I’m legally blind to begin with, but even with seriously impaired vision, blood sugar fluctuations have a major, major impact on how well I can see. When blood sugars swing between high and low, it causes the lens to swell to varying degrees, which can effectively make it so that one has varying refractive errors. This is not the same as diabetic retinopathy, which is damage to the retina that (once it starts to affect vision) is not reversable.

Hmm I knew blood sugar variations could cause temporary changes and blurred vision/myopia was a big symptom when I was first diagnosed, but it cleared up in about 2 weeks after starting insulin. My need for glasses came later though and seemed permanent, but I’m wondering if it’s because when my A1Cs started approaching 7 I spent years with fasting blood sugars between 7-9 instead of 4-6. Even though it has gotten much better, is the bit of myopia I still have permanent, or will it continue to get better as I maintain normal blood sugars most of the time?

I’ve recently gotten glasses for astigmatism and a bit of magnification, so you can definitely still need glasses. In my late teens and early 20s I went through several years where my vision dropped off dramatically—like I could only see shapes and colours (keeping in mind that I’m starting from a place of low vision). I had no idea at the time that diabetes could temporarily affect vision, and I assumed the vision loss was permanent. At the time I was using NPH and my blood sugar, of course, was all over the place with an A1c of around 8.5%, give or take (growing up my parents had helped me keep my A1c at around 7.0% through strict diet, which went out the window when I took control). Then, when I started Lantus years later, my vision suddenly improved dramatically over the course of about a week (and my A1c also dropped from 8.3% to 7.1%). I honestly thought I was going crazy at first until I learned that diabetes can, in fact, affect the way the eye focuses. So, I think if you have improved control, you’ll notice changes fairly quickly. My vision still changes if I’m having a rough period with blood sugar swings, but now I know it’s from diabetes and is only temporary.

I had vision changes when I first started controlling my BG - the change was a bit odd in my case, though. Magnification didn’t change, but they had to remove the correction for astigmatism that I’d ALWAYS needed before that point! They did increase the reading portion of my lenses, but that’s more age-related than anything else. No one knows why working on my diabetes would have corrected my eyes that way, but that’s what happened.

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