title: Functional outcome of subthreshold versus threshold diode laser photocoagulation in diabetic macular oedema.
abstract: OBJECTIVE
  To compare the efficacy of subthreshold diode laser photocoagulation with conventional threshold diode laser in clinically significant macular oedema (CSME) in diabetics.
  
  
  METHODS
  Prospective randomised controlled trial. Thirty eyes of 20 patients with CSME having central macular thickness (CMT) >or=250 microm on optical coherence tomography (OCT) and best corrected Snellen visual acuity (BCVA) of 20/80 or better were randomly assigned to receive subthreshold diode laser (group A) or threshold laser (group B). The clinical course of BCVA, CMT on OCT, photo stress recovery time (PSRT), contrast sensitivity (CS) using Pelli Robson chart, and central visual field (10-2 VF, Humphrey Field Analyser II) were monitored regularly for 18 weeks after intervention.
  
  
  RESULTS
  Both groups showed significant (P=0.03) and comparable improvement in mean BCVA at 18 weeks visit. There were also significant and comparable reductions (P<0.01) in mean CMT at all visits compared with baseline in both groups. PSRT and CS (75+/-16 (mean+/-SD) and 0.72+/-0.3 in group A and 81+/-12 and 0.68+/-0.2 in group B pre-laser) were significantly better in group A at the final visit (66+/-17 and 1.04+/-0.3) as compared to group B (78+/-11 and 0.73+/-0.3). One patient in group B showed a paracentral scotoma on 10-2 VF after the laser, which persisted till the end of follow-up.
  
  
  CONCLUSIONS
  Subthreshold diode laser photocoagulation is as effective as conventional threshold laser in reducing or eliminating diabetic macular oedema (on OCT) and in improving BCVA. Recovery of macular function as assessed by CS and PSRT maybe better with subthreshold laser.
authors.affiliation: Guru Nanak Eye Centre, Maulana Azad Medical College, New Delhi, India.
authors.forename: V
authors.initials: V
authors.lastname: Kumar
authors.forename: B
authors.initials: B
authors.lastname: Ghosh
authors.forename: D K
authors.initials: DK
authors.lastname: Mehta
authors.forename: N
authors.initials: N
authors.lastname: Goel
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology; D003930:Diabetic Retinopathy / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D008269:Macular Edema / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D014787:Vision Tests; D014792:Visual Acuity; D014794:Visual Fields / Q000502:physiology