My diabetic patient complains of acute blurred vision past few days since her blood glucoses have been out of control. How does high blood glucose affect the vision acutely?

“Vision loss or blurriness” is one of the most common manifestations of acute hyperglycemia in diabetic patients and is due to the osmotic swelling of the lens resulting in changes in its characteristics and the inability to properly focus an image.1

Since glucose acts as a solute, an increase in the concentration of glucose causes a rise in osmotic forces and movement of fluid into the lens, resulting in transient myopia. Interestingly, the increase in the fluid in the lens causes a change in its refractory index which is associated with focusing an image at a different length; it does not affect  its curvature or position. 

Baseline vision should be eventually restored by correcting glucose levels.2 Also remember that rapid correction of hyperglycemia may make the lens swelling worse, causing increased visual disturbances.3  

Fun fact: Did you know that chronic hyperglycemia is associated with cataract formation due to excess conversion of glucose to sorbitol in the lens? 4

References

  1. Bron A.J, Sparrow J, Brown N, Harding J, Blakytny, R. The Lens in Diabetes. Eye 1993; 7: 260-75 https://www.nature.com/articles/eye199360.pdf
  2. Huntjens B. O’Donnell C. Refractive error changes in Diabetes Mellitus. Optometry in Practice 2006; 7:103-114. http://openaccess.city.ac.uk/6185/3/Refractive_Error_Changes_in_DM_FINAL.pdf
  3. Sychev YV, Zepeda EM, Lam DL. Bilateral cateract formation via acute spontaneous fracture of the lens following treatment of hyperglycemic hyperosmolar syndrome: Case report. Am J Ophthalmol 2017;7:66-69. https://www.ncbi.nlm.nih.gov/pubmed/29260081
  4. Pollreisz A, Ursula SE. Diabetic Cataract—Pathogenesis, Epidemiology and Treatment. Journal of Ophthalmology 2010; vol. 2010, Article ID 608751. https://www.hindawi.com/journals/joph/2010/608751

 

Contributed by Felicia Hsu, Medical Student, Harvard Medical School

My diabetic patient complains of acute blurred vision past few days since her blood glucoses have been out of control. How does high blood glucose affect the vision acutely?

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