According to the Early Treatment Diabetic Retinopathy Study (ETDRS), the indication for macular laser photocoagulation in diabetic macular edema (DME) is:

• A Any thickening of the retina within 1 disc diameter of the centre of the fovea
• B Visual acuity worse than 6/18 with any macular edema
• C Clinically significant macular edema (CSME) — defined as thickening within 500 µm of foveal centre, hard exudates within 500 µm of centre with adjacent thickening, or retinal thickening ≥1 disc area within 1 disc diameter ✓
• D Fluorescein leakage from microaneurysms regardless of retinal thickening

Explanation

The ETDRS defined Clinically Significant Macular Edema (CSME) with three criteria: retinal thickening within 500 µm of the foveal centre; hard exudates within 500 µm of the centre with adjacent retinal thickening; or a zone of retinal thickening at least 1 disc area in size within 1 disc diameter of the centre. CSME is an indication for focal/grid laser regardless of visual acuity. However, anti-VEGF therapy (ranibizumab, bevacizumab, aflibercept) has now superseded laser as first-line for centre-involving DME with vision loss, but CSME definition remains the historical landmark criterion.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.