diabetic macular oedema

Last edited 12/2020 and last reviewed 09/2022

Diabetic macular edema (DME) is the most common cause of visual loss in those with diabetic retinopathy and is increasing in prevalence globally (1)

• prevalence of DME in patients with diabetic retinopathy is 2.7%–11% and it depends on the type of diabetes and the duration of the disease, but for both types 1 and 2 after 25-years duration, it approximates 30% (2)
• systemic factors associated with DME include longer duration of diabetes, higher systolic blood pressure, and higher hemoglobin A1C
• sole ocular factor associated with DME is diabetic retinopathy severity as increasing severity is associated with increasing prevalence of DME

DME is caused by diabetic retinopathy (DR), the most frequent and severe ocular complication of diabetes mellitus. DR is the leading cause of blindness in the working-age population in high-income countries (4,5).

DME is the swelling of the retina resulting from the exudation and accumulation of extracellular fluid and proteins in the macula (3), due to the breakdown of the blood-retina barrier with an increase in vascular permeability (4,5)

• Intraretinal fluid accumulation results in significant reduction invisual acuity that may be reversible in the short term, but prolonged edema can
  cause irreversible damage resulting in permanent visual loss

The most common presenting clinical symptom of DME is blurred vision. Other symptoms can include metamorphopsia (distortion of visual image), floaters, change in contrast sensitivity, photophobia (visual intolerance to light), changes in color vision, and scotomas (localized defects of visual field)

• diagnosis is made by finding macular edema due to diabetes on the clinical examination
• in general, requires direct visualization of the macular edema that uses a high magnification stereoscopic lens system designed to view the ocular fundus - If the thickening is sufficiently severe it can be seen with an indirect ophthalmoscope
• although stereoscopic observation of the fundus is considered to be the most accepted method of diagnosing DME, there is an increased use of other diagnostic tools such as stereo fundus photography, fluorescein angiography, and more recently, optical coherence tomography (6)

Chronic DME can be associated with cystoid macular edema (CME), cystic degeneration of the macular retina

• if CME is present, it might be visible with a handheld non-stereoscopic direct ophthalmoscope Although stereoscopic observation of the fundus is considered to be the most accepted method of diagnosing DME, there is an increased use of other diagnostic tools such as stereo fundus
  photography, fluorescein angiography, and more recently, optical coherence tomography (6)

Reference:

• Klein R, Klein BE, Moss SE, Cruickshanks KJ. The Wisconsin epidemiologic study of diabetic retinopathy. XV. The long-term incidence of macular edema. Ophthalmology. 1995;102:7–16
• Browning DJ et al. Diabetic macular edema: Evidence-based management. Indian J Ophthalmol. 2018 Dec; 66(12): 1736–1750.
• Ciulla TA et al. Diabetic retinopathy and diabetic macular edema: pathophysiology, screening, and novel therapies. Diabetes Care 2003;26(9):2653-64.
• Antcliff RJ, Marshall J. The pathogenesis of edema in diabetic maculopathy. Seminars in Ophthalmology 1999;14(4):223-32.Yau JW et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care 2012;35(3):556-64.
• Virgil G et al. Anti-vascular endothelial growth factor for diabetic macular oedema: a network meta-analysis. Cochrane Database of
Systematic Reviews 2017, Issue 6. Art. No: CD007419. [DOI: 10.1002/14651858.CD007419.pub5]