Background:

Diabetic macular edema (DME) is a frequent complication of diabetic retinopathy. It is characterized to increased vascular permeability, due to blood-retinal barriers breakdown. Since macular laser treatment has shown poor efficacy to diffuse edema, surgical option of therapy is discussed. Several studies have proven the efficacy of pars plana vitrectomy (PPV) with inner limiting membrane (ILM) peeling in case of DME with a tractional component. Less is known in case of DME without tractional component.

Purpose:

To evaluate long-term anatomic and functional outcomes of PPV and ILM peeling in eyes with clinically significant diabetic macular edema (CSME).

Methods:

Retrospective, observational study based on the data of 74 eyes of 52 consecutive patients with CSME that underwent PPV and ILM peeling, performed by the same surgeon (G.P.). Inclusion criteria were one of the following: presence of vitreoretinal interface abnormalities on optical coherence tomography (OCT), large hard exudates involving or threatening the foveal centre, macular thickness exceeding 450 microns, unresponsive to other treatments CSME. Eyes were divided into two groups, with and without vitreoretinal interface abnormalities (namely group A and group B). Visual acuity (BCVA) and OCT were performed at baseline and postoperatively during follow up. Foveal thickness (FT) and total macular volume (TMV) were considered. Follow up ranged from 12 to 48 months (30 ±18).

Results:

BCVA significantly increased in both groups twelve months after treatment  (P=0.0001). Two years follow-up data were available for 45 of 74 eyes (60.8%): BCVA remained stable in 40 eyes (88.9%; 21 eyes in group A, 19 eyes in group B), and worsened in 5 eyes (11.1%; 3 eyes in group A, 2 eyes in group B). Three years follow-up data were available for 33 of 74 eyes (44.6%): BCVA remained stable in 26 eyes (78.8%; 16 eyes in group A, 10 eyes in group B), and worsened in 6 eyes (18.2%; 4 eyes in group A, 2 eyes in group B). OCT evaluations showed a significant reduction after 12 months and was maintained for the entire follow up, except for 3 eyes (4%) that worsened significantly after 24 months, and needed additional treatments (macular grid in 2 cases, intravitreal triamcinolone in 1 case). No significant differences were also observed when TMV was considered. Moreover, eyes with a higher FT were more likely to worsen during follow-up over the eyes with a lower FT, both in group A and B.

Conclusions:

In selected patients PPV with ILM peeling could lead to significant reduction of CSME and improvement of BCVA, regardless the presence of vitreoretinal abnormalities on OCT. In addition, FT reduction and visual improvement might persist up to 36 months.