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From Oakland, California, USA:

I am an optometrist, and had a 40-something year old diabetic patient who came in for an eye exam a few weeks after a kidney transplant. After the surgery, they had a hard time controlling his blood sugar. For about two to three days, it was around 400 mg/dl [22.2 mmol/L].

His refraction was similar to previous exams. But, he came in three weeks later because his new glasses weren't working for him. I rechecked his refraction and it had shifted by -1.50 diopters (more myopic). He said his blood sugar was now down to normal, around 120 mg/dl [6.7 mmol/L]. Does the refractive shift commonly lag changes in blood sugar? If he stays under good control, about how long would it take for his refraction to return to normal?


You pose excellent questions. I am giving a talk on this very topic before the Maine Optometric Association this Fall. It is my experience that refractive changes do not substantially lag blood glucose changes; typically, the effects are seen within one week. When glycemic control improves dramatically, there is typically a myopic shift (I have seen changes ranging from -0.50 to -4.00 diopters sphere) whereas worsening glycemic control tends to result in decreased myopia/increased hyperopia. In your patient's particular case, it is likely that corticosteroid use following transplantation worsened glycemic control and altered fluid balance (by multiple mechanisms) resulting in a hyperopic shift. I suspect his glycemic control was chronically sub-optimal, hence the relative refractive stability you indicate. I always recommend that eye doctors use glycosylated hemoglobin (A1c) as the benchmark for refractive stability; in my own practice, I usually prescribe when the A1c is below 7%. As an adjunct, it is wise to look at the patient's blood glucose log book.


Original posting 15 Aug 2004
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