• Macular thickness measured by optical coherence tomography (OCT) [ Time Frame: 12 months ]
• Best corrected visual acuity [ Time Frame: 12 months ]

• Safety profile [ Time Frame: 12 months ] [ Designated as safety issue: Yes ]
• Selectivity of laser therapy (autofluorescence and mfERG) [ Time Frame: 12 months ] [ Designated as safety issue: Yes ]

• Safety profile [ Time Frame: 12 months ]
• Selectivity of laser therapy (autofluorescence and mfERG) [ Time Frame: 12 months ]

Objective: To compare micropulse 810nm diode laser photocoagulation versus argon laser photocoagulation for treatment of diabetic macular edema. Micropulse laser technique will be determined by an initial clinical trial comparing single versus double density laser photocoagulation techniques for treatment of diabetic macular edema.The single density is based on the Early Treatment Diabetic Retinopathy Study (ETDRS) grid photocoagulation technique and the double density increases the number of spots.

Methods: Patients with diabetic macular edema will be assigned to receive either micropulse 810nm diode laser photocoagulation or argon laser photocoagulation therapy. First, in a smaller clinical trial, patients will be assigned to single or double density micropulse 810nm diode laser to determine best strategy for this therapy. Visual acuity, fundus photographs and fluorescein angiography, and optical coherence tomography measurements , autofluorescence and mfERG were obtained at baseline and at 1, 3 and 6 months and 12 months.

• Experimental: Micropulse 810nm diode laser
• Active Comparator: Argon laser photocoagulation

Inclusion Criteria:

• Diabetes mellitus (type 1 or 2)
• Diabetic macular edema in study eye associated to diabetic retinopathy
• Diffuse macular edema defined as macular thickening determined by biomicroscopy and fluorescein angiography.
• Best corrected visual acuity between 34 (20/200) and 68 letters (20/50).
• Macular thickness greater than 300 mcm on OCT.

Exclusion Criteria:

• Uncontrolled systemic disease
• Start of medical therapy for diabetes or change in treatment from oral to insulin four months before initial visit.
• HbA1c levels greater than 10%
• Presence of retinal venous occlusion, cystoid macular edema,or other condition that would contribute to macular edema.
• Presence of epiretinal membrane
• Presence of vitreomacular traction in the study eye.
• Neovascularization of disc or elsewhere in the study eye.
• History or presence of choroidal neovascularization in the study eye.
• Presence of rubeosis irides in the study eye.
• Eye opacity that interfere with clinical documentation and photography.
• Intra-ocular surgery 90 days before initial visit.
• Scheduled surgery for study eye.
• Patients with known allergies to fluorescein.