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Clinical science
Prospective randomised controlled trial comparing sub-threshold micropulse diode laser photocoagulation and conventional green laser for clinically significant diabetic macular oedema
  1. J Figueira1,
  2. J Khan2,
  3. S Nunes1,
  4. S Sivaprasad2,
  5. A Rosa1,
  6. J F de Abreu1,
  7. J G Cunha-Vaz1,
  8. N V Chong2
  1. 1
    University Hospital and Institute of Biomedical Research on Light and Image, Faculty of Medicine, University of Coimbra, Portugal
  2. 2
    Laser and Retinal Research Unit, King’s College Hospital, London, UK
  1. Correspondence to Dr N V Chong, Oxford Eye Hospital, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; victor{at}


Aim: The study was a prospective randomised controlled double-masked trial performed in two centres to compare sub-threshold micropulse diode laser photocoagulation (MPDL) with conventional green laser photocoagulation (CGL) in the treatment of clinically significant diabetic macular oedema (CSMO).

Methods: Fifty-three patients (84 eyes) with diabetic CSMO were randomly assigned to MPDL (n = 44) or CGL (n = 40) according to the modified Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. Treatments were performed after baseline and re-treatments were allowed at or after the 4 month visit if necessary. Parameters noted included the best corrected visual acuity (BCVA), colour fundus photographs, central retinal thickness using optical coherence tomography (OCT), vision contrast sensitivity with Pelli–Robson charts and presence of visible laser scars at baseline and at 4 and 12 months. The primary outcome was BCVA at 12 months.

Results: All patients completed 12 months of follow-up after treatment at baseline. There were no statistically significant differences in BCVA, contrast sensitivity and retinal thickness between the two laser modalities at 0, 4 and 12 months. We found that laser scarring was much more apparent with CGL than with the sub-threshold approach (MPDL). Laser scars were identified at the 12 month visits in 13.9% of the MPDL-treated eyes compared with 59.0% of the CGL-treated eyes (p<0.001).

Conclusion: Sub-threshold micropulse diode laser photocoagulation is equally as effective as CGL treatment for CSMO.

Trial registration number: ISTRN 90646644.

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  • Competing interests None declared.

  • Ethics approval The study was approved by Local Research Ethical Committee and Institutional Review Board at both centres.

  • Patient consent Obtained.

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