الفهرس 
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Abstract
DME is a serious consequence of diabetes that affects more than 20 million individuals globally and can result in blindness and visual impairment.
Optical coherence tomography (OCT) is a non-invasive tool that enables assesment of the morphology of layers of the retina .
Multifocal electroretinography (mfERG) is a non-invasive test that permits to objectively evaluate the macula’s functioning state.
This study aimed To evaluate macular functional changes detected by mERG and visual acuity assessment in relation to different morphological patterns of diabetic macular edema detected by OCT.
This study was a case control study that included 160 eyes of 160 participants that were divided into 2 groups: group I included 60 eyes of 60 normal subject as a control group, group II included 100 eyes of 100 patients with DME.
Diabetic macular oedema was divided according to OCT findings to 4 types
1- Type 1 : diffuse retinal thickening
2- Type 2 : cystoid macular oedema
3- Type 3 : neurosensory detachment
4- Type 4 : combined type that was subdivided into :
Type 4 a : diffuse retinal thickening with cystoid macular oedema
Type 4 b : diffuse retinal thickening with neurosensory detachment
Type 4 c: cystoid macular oedema with neurosensory detachment
Type of macular oedema was determined in central 500 um centered on the fovea (250 um on each side) and was also determined in paracentral 1000 um that surround previous central circle (500 um on each side of previous central circle)
In all study groups, we examined the responses of mfERG based on regional averages from two concentric rings centred on the fovea (0°-2°, 2°-5°). In the initial phase, we analyzed control and diabetic eyes’ mfERG amplitudes and latencies of P1 in the two-ring retinal areas. The next phase was doing a correlation analysis between measurements of the central 2 rings’ mfERG amplitude and latency, BCVA and central macular thickness (CMT)
The mean age in group 1 was 52.75 ± 9.07 years (range, 36-66 years). The mean age in group 2 was 57.7 ± 8.4 years (range, 35-75 years) without statistically significant variations between two groups .There were considerable differences in mfERG values in two ring areas of the retina between cases and control groups The mean amplitude of the P1 wave in R1 (foveola) on group II was 29.73 ± 19.87nV/deg while The mean amplitude of the P1 wave in R1 (foveola) on control group was 73.1 ± 15.54nV/deg The mean implicit time of the P1 wave in R1 (foveola) on group II was 49.74 ± 5.78 ms while The mean implicit time of the P1 wave in R1 (foveola) on control group was 45.9 ± 1.82 ms .
Central macular thickness (CMT) had a considerable negative relation with P1 amplitude in the central ring1 (r = -0.280, P = 0.005) in diabetic group. While CMT had a considerable positive relation with P1 implicit time in the central ring (r = 0.283, P = 0.004) in diabetic group
Analysis of correlation between each type of DME and mfERG parameters. Type 1 (diffuse retinal thickening) had the highest P1 wave amplitude in the central 2 rings. BCVA was best in type 1 with marked difference from type 2 and type 4c. Therefor type 1 DME had the most favorable prognosis.
Comparing type 2 (cystoid macular oedema) to type 1, This study observed that type 2 was significantly correlated with reduction of P1 wave amplitude in central macular ring.
In type 2 BCVA was likewise significantly diminished in comparison to type1. type 3 (NSD) was associated with evident reduction of P1 wave amplitude in comparison with type 1 in ring 2.
type 4C (combined cystoid macular oedema with neurosensory detachment) in central and paracentral rings had the lowest P1 wave amplitude, the most prolonged implicit time and the worst BCVA, Therefor presence of SRF with multiple cystoid spaces in DME was associated with reduced P1 wave amplitude and prolonged P1 wave implicit time in central and paracentral rings and this was a bad prognostic sign for DME.