Purpose. To determine the effectiveness and safety of diode laser, pars plana vitrectomy (PPV) with gas tamponade, and intravitreal triamcinolone (IVT) as possible treatments for diffuse diabetic macular edema (dDME).
To determine whether the new macular edema Classification previously proposed by some of the authors may help as a guide in the choice of treatment.
Methods. A retrospective, comparative study of 169 eyes with dDME that underwent treatment. The eyes were
divided into 3 groups: in the PPV Group, 59 eyes received PPV with gas tamponade; in the DIODE Group, 53 eyes
received a laser grid; in the IVT Group, 57 eyes received an intravitreal injection of 4mg of triamcinolone acetonide. The follow up ranged from 6 to 24 months. The eyes were classified according to the new DME Classification based on OCT.
Main outcomes. Change in foveal thickness as determined by Optical Coherence Tomography (OCT); change in visual acuity; intra and postoperative complications.
Results. Mean visual acuity (VA) improved at 3 months with every treatment. At one year only eyes which underwent PPV still had a better VA than the pre-op value, while eyes which underwent IVT and laser treatment showed regression. PPV show the greater percentage of eyes which gain 3 or more lines of VA at one year (17%).
Mean foveal thickness improved at 3 months with every treatment. Only the eyes into the PPV Group showed relatively low foveal thickness at one year.
Better final VA and foveal thickness were obtained if preop VA is 
0.3 and if earlier stages of DME were treated
according to the new DME Classification.
PPV was the treatment which offered the most stable results with at one year or longer. Similar results were
observed into the PPV Groups as a whole and into a subgroup of eyes with preoperative PVD.
No complications were encountered with laser diode treatment. Long term complications into the IVT Group were elevated IOP (8%), retinal detachment (3.5%) and posterior cataract (15%).
Long term complications into the PPV Group were retinal detachment (3.4%) and cataract (90%).
Conclusions. Diode laser, PPV with gas tamponade and IVT are effective alternative treatments to decrease foveal
thickness and improve visual acuity in eyes with DME.
However while the results of PPV are stable in the long term follow-up, diode laser and IVT do not offer stable results. Complications may be severe with PPV and IVT. It is necessary to carefully select cases which would benefit
from these types of treatments. The authors think that the OCT Classification may serve as a guide for the choice of
treatment.

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