Blurry vision may be a sign of any of a number of disorders associated with the diabetes-related eye, including proliferative diabetes-related retinopathy, macular edema, glaucoma or cataracts. For additional information on these and other ocular disorders of the diabetes-related eye please see the focus on disease specific locations of this tool kit.
With the onset of diabetes and when regulating blood glucose levels with treatment, disturbances in vision can occur, however for many people once blood sugars stabilize so too does their vision. Your optometrist should not alter your prescription lens until your glucose levels have been stabilized. Often when blood glucose levels have been stabilized disturbances in your everyday vision may resolve.
Your everyday prescription lens is usually due to refractive error which means that the shape of your eye does not bend light correctly, resulting in a blurred image. The main types of refractive errors are myopia (near-sightedness), hyperopia (far-sightedness), presbyopia (normal loss of near vision with age making it difficult to read at close range), and astigmatism which occurs when the surface of the eye (cornea) or the lens behind it is not a round shape, but oval like a rugby ball. This distorts the light entering the eye causing blurred vision at all distances.
According to the WHO globally 153 million people over the age of 5 are visually impaired due to uncorrected refractive error, thus many people have refractive error before the onset of diabetes. Temporary refractive error occurs during the course of diabetes and is associated with treatment induced changes in blood glucose levels. During hyperglycaemia when blood glucose levels are too high myopia (near-sightedness) can develop, and during hypoglycaemia when glucose levels are low hyperopia (far-sightedness) can develop in patients with diabetes 2. A systematic review and meta-analysis reported that patients with diabetes with myopia were less likely to develop sight threatening diabetes-related retinopathy and this is associated with an increased distance from the front to the back of the eye (axial length) 3.