What causes DME?

About DME

The swelling in the macula, seen with DME, is caused by the leakage of fluid into the area.

Fluid leaks into the macula when blood vessels in the area become damaged. This is why people with diabetes are likely to develop DME if they have another complication known as diabetic retinopathy (DR).¹ In DR, the blood vessels in the eye grow abnormally, which causes eyesight issues. However, if high blood sugar levels proceed to damage these vessels, they will bleed, causing the fluid buildup characteristic of DME.²

4 boxes labelled 1 to 4 with arrows between them. The first box contains an image of a blood drop with a magnifying glass that shows sugar in the blood and the text “High levels of sugar in the blood…”, the second box shows a broken blood vessel and the text “...cause damage to the blood vessels”, the third box has arrows leaving the blood vessel and the text “fluid leaks out of the damaged vessels”, and the final box contains a cross section of an eye with pressure written inside and the text “causing swelling in the eye (reference 2).”.

High blood sugar is not the only factor that will increase the risk of blood vessels rupturing or indeed forming to begin with; other risk factors have been associated with the likelihood of DME developing in diabetics.

4 circles in a row. The first contains a line drawing of blood vessels and the caption “diabetic retinopathy”, the second contains a line drawing of a blood drop and sugar and has the caption “poorly managed diabetes”, the third contains a line drawing of a cigarette and the caption “a history of smoking”, and the last contains a line drawing of a blood pressure band and the caption “high cholesterol and blood pressure” (reference 1).

The events underpinning abnormal blood vessel growth are similar to those seen in other macular diseases, including wet AMD and RVO. These events are thought to be linked to a protein called vascular endothelial growth factor (VEGF). This protein helps blood vessels to grow; however, in these diseases, VEGF causes abnormal blood vessels to grow in the back of the eye that ultimately damage the macula.^2,3

References

Macular Society. Diabetic macular oedema (DMO). Available at: https://www.macularsociety.org/macular-disease/macular-conditions/diabetic-macular-oedema/.. Last accessed April 2025
NHS. Diabetic macula oedema treatment pathway. Available at: https://mft.nhs.uk/app/uploads/sites/2/2018/05/REH-217-Diabetic-Macular-Oedema-1.pdf. Last accessed April 2025
Johns Hopkins Medicine. Age-Related Macular Degeneration (AMD). Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/agerelated-macular-degeneration-amd. Last accessed April 2025.