This study will investigate the clinical efficacy and safety of the PASCAL laser (PAttern SCAn Laser) for diabetic retinopathy. Patients with proliferative or severe nonproliferative retinopathy will be treated with panretinal photocoagulation utilizing different treatment strategies. The investigators believe that using "lower" laser parameters, the clinical response may be equivalent with less adverse effects.

Inclusion Criteria:

• proliferative or severe nonproliferative diabetic retinopathy (type 1 or type 2)
• best corrected visual acuity of 20/50 or better
• capability to read and follow instructions
• capability to sign the consignment term

Exclusion Criteria:

• best corrected visual acuity worse than 20/50
• significant macular edema responsible for visual acuity lower than 20/50
• media opacities (includes vitreous hemorrhage in the visual axis, but not a reabsorbing inferior vitreous hemorrhage)
• previous laser treatment (PRP, focal or macular grid)
• glaucoma (confirmed or suspicious)
• other diseases of the retina and optic nerve
• previous ocular surgery in the last 6 months
• impossibility to obtain good quality images of retinography, angiography or OCT