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What Causes a Myopic Shift?
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A myopic shift is an increase in the degree of nearsightedness. This can be due to natural aging of the eye, but it can also be the result of cataracts or diabetes. This may or may not lead to extreme myopia.
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For cataracts, this can be when the protein clumps form over the nucleus of the lens, causing the greatest opacity. The treatment is usually surgery.
With diabetes, this is generally the result of an increase in blood pressure. Treatment usually entails monitoring glucose levels.
Causes of Myopic Shifts
A myopic shift takes place when a person becomes increasingly shortsighted, so they require a stronger prescription for their eyeglasses. Myopia, by definition, means being nearsighted, so the “shift” is the change in vision toward a greater degree of nearsightedness.
There are a number of factors that can cause a myopic shift. In many cases, the change is quite normal for teenagers and people in their 20s. However, most people will experience myopic shift as the result of the development of cataracts. Cataracts are formed by clumps of inactive proteins forming on the lens of the eye, occluding vision and causing the shortsightedness.
For patients who have undiagnosed diabetes or who are not properly controlling their diabetes, myopic shifts may occur in both eyes. This is because the lens becomes swollen due to an increased blood pressure.
Nuclear Cataracts
Usually, treatment for a myopic shift is to update your eyeglass prescription, to give you clearer vision. In the event of cataracts, you will likely need cataract surgery to replace your eye’s natural lens. If the diagnosis is diabetes, you would have to start treatment to monitor your blood sugar levels.
Of the different ways that cataracts form, the kind that is most typically responsible for the development of myopic shift are nuclear cataracts. They are called this because they form in the nucleus, or the center, of the lens.
Nuclear cataracts are a normal part of aging. They are not serious in and of themselves, although they can make it harder to see, which can cause problems with everyday life. Researchers writing in the Investigative Ophthalmology and Visual Science journal found that “nuclear cataracts are the primary contributor to a myopic shift among older patients.”
Another article in the same journal noted that the denser the cataracts on the nucleus, the greater the opacity (cloudiness), and thus the stronger the degree of myopic shift. Knowing how much the lens is clouded over, and where exactly this happens, is useful for the ophthalmologist who will be treating the problem.
Diabetes Treatment
In the case of diabetes, Danish researchers found that “poor metabolic control of glucose” may be a factor in the development of myopic shift. Writing in the Acta Ophthalmologica Scandinavica journal, they argue that the increasing shortsightedness of myopic onset could be a complication of hyperglycemia in diabetes.
While the effects of diabetes on the eyes have been long known, other researchers were interested in the possibility of learning more about the connection. This was important so ophthalmologists could make a connection to diabetes if their patients’ myopic shift cannot be explained by other factors.
As with all forms of cataracts, the best way of treating them (and thus addressing the myopic shift) is cataract surgery. The natural lens of the eye (on which the protein clumps have grown) is replaced with an intraocular lens (on which protein clumps cannot grow). It might still be necessary for a patient to wear some form of corrective eyewear, but the combination of surgery and corrective eyewear should successfully remedy the myopic shift.
References
- Refraction in Adults with Diabetes. (January 2011). Epidemiology.
- Refraction and Change in Refraction Over a 20-Year Period in the Beaver Dam Eye Study. (September 2018). Investigative Ophthalmology and Visual Science.
- Prevalence of Myopic Shifts in Patients Seeking Cataract Surgery. (March 2012). Investigative Ophthalmology and Visual Science.
- Myopia and Diabetes Mellitus With Special Reference to Adult‐Onset Myopia. (February 1986). Acta Ophthalmologica Scandinavica.
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