1. assessment the outcomes of vitrectomy on retinal function by mf-ERG (multifocal electroretinogram) and anatomy by OCT (optical coherence tomography) in patients with tractional diabetic macular edema (TDME) .
2. To correlate the postoperative corrected distance visual acuity (CDVA) with the mf-ERG and OCT findings following vitrectomy surgery for TDME.

Diabetic retinopathy (DR) is one of the leading causes of vision loss worldwide [1]. In 2010, DR affected more than 93 million individuals worldwide, 28 million of whom experienced vision-threatening DR[2].

Diabetic macular edema (DME) is a common cause of visual loss in diabetic retinopathy (DR) and is a complication in any stages of DR including proliferative diabetic retinopathy (PDR)[3].

The terms vitreous traction maculopathy, vitreous induced diabetic macular edema and maculopathy due to posterior hyaloid traction are synonymous and describe a pattern of diabetic maculopathy which is characterized by: (1) The absence of complete posterior vitreous detachment; (2) An increased retinal thickness in the center of the macula, and (3) a characteristic reflex of the vitreoretinal interface[4]. there are multiple factors in the vitreomacular interface including ERM, taut posterior cortices, vitreoschisis, PVD, and adhesions [5]. Anomalous PVD generates antero-posterior and tangential traction forces at the vitreo-retinal interface that act upon the inner and outer retinal layers [6]. Until recently, the only treatment option available for VMA was vitrectomy[7].

Few studies have used the multifocal electroretinogram (mfERG) technique to investigate the effects of vitrectomy on macular visual function for DME [8]. Mf-ERG is an objective electrophysiologic technique that measures the electrical changes in the central retinal area. This technique accurately assess the electrophysiologic activity in multiple retinal areas, and gives us a topographic charting of retinal function [9] .

Inclusion Criteria:

• Age ≥18 years; type 1 or 2 diabetes
• TDME as the indication for vitrectomy; central foveal thickness (CFT) ≥300 µm as measured by spectral-domain optical coherence tomography (SD-OCT) , We defined VMIA on OCT as ERM, anomalous vitreomacular adhesions, or both , ), and possible visual acuity impairment attributed to foveal thickening due to DME.

Exclusion Criteria:

• A history of other retinal diseases; or active ocular inflammation or infection or glaucoma .
• Eyes with macular edema from etiologies other than diabetes
• Dense refractive media opacity before and after surgery, such as dense cataract, vitreous hemorrhage which can conceal fundus visualization and OCT measurements
• Central retinal ischemia detected by intravenous fluorescein angiograms.
• A history of vitrectomy
• A visual acuity worse than 1\60 and the duration of tractional ERM is more than 12 months.

eyes with tractional diabetic macular edema