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Abstract Diabetic macular edema (DME) is an insult to the macula during the course of diabetic retinopathy. DME is a major cause of visual deterioration in diabetic retinopathy. The prevalence of DME increases with increased duration of diabetes and severity of retinopathy. The incidence reaches its maximum in those old patients treated with insulin. Some systemic factors as the poor blood sugar control, hypertension, and renal failure, may lead to deterioration of DME. The concern in studying DME is directed towards detection of vision threatening changes as they become clinically detectable and hence we can avoid irreversible damage to the retinal elements in this group of patients. In this study we studied 82 eyes of 45 subjects, classified into two groups; group A containing 46 eyes of 27 diabetic patients with clinically DME and group B containing 36 eyes of 18 normal subjects who represented the control group. Patients and control were examined with OCT and ERG, both conventional and multifocal aiming at analyzing morphological and functional aspects of DME to correlate them with each other and with visual acuity. OCT examination revealed 3 patterns of retinal structural changes in DME, namely sponge like swelling in 43.5%, cystic changes in 41.3%, and serous retinal detachment in 15.2% of diabetic eyes, and according to these findings patients were classified into 3 subgroups 1, 2, and 3. Foveal thickness in the control group was 179.4 ± 19.5 μm. In the diabetic patients there was a significant increase in foveal thickness to 297.41 ± 94.6 μm. Also, this increase in foveal thickness was highly correlated with BCVA (r=-0.75, p<0.001), and this was the case in the __Summary__________________________________________________________ 128 different study subgroups. It was observed that foveal thickness was steadily and significantly increased from subgroup 1 to subgroup 3. ERG examination revealed statistically significant reduction in b-wave amplitude of scotopic and photopic ERG with significant prolongation in implicit time. Also, there was significant reduction in the OPs, and 30 Hz flicker amplitude with prolongation of its implicit time. These changes were observed in group (A), as well as in all subgroups when their ERG results compared with the group (B). However, the correlations of these results with both foveal thickness and BCVA were non significant in most ERG tests. So, from this study we conclude that conventional ERG not with benefit in cases of diabetic macular edema as the results obtained showed no valuable significant correlation between macular thickness and latency or amplitude at scotopic or photopic conditions. In case of mf-ERG it was found that the results of N1 latency, P1 latency and P1 amplitude mainly at all patients of the diabetic group and different subgroups were reduced and this reduction was statistically highly significant with p value <0.001. The correlation of mf-ERG results, with both foveal thickness and BCVA was statistically significant in contrast to the correlation of the conventional full field ERG with these two variants. These findings agree with previous studies that mentioned that foveal thickness is better correlated with visual acuity, and mf-ERG is superior in studying localized retinal pathology, as in cases of DME. So, we can conclude that OCT is an objective and sensitive method to detect and quantify pattern of diabetic macular edema within the retina and its thickness. Both foveal thickness determined by OCT, and foveal function determined by mf-ERG are better correlated with BCVA as we found at our study a highly significant negative correlation between them. __Summary__________________________________________________________ 129 In conclusion; the advantage of mf ERG over conventional ERG included in explanation of macular area by zone analysis that specific to each diabetic subgroup as decreased amplitude p1 , prolonged latency p1 at rings 2,3 and 4 characteristic to subgroupA1 , and rings 1,2 and 3 to subgroup A2 and all 5 rings to subgroup A3. The combination of OCT and mfERG provides objective criteria for evaluation of DME. In this study, evidence was provided for that serous retinal detachment may be the most important retinal function threatening pathological changes in DME. Treatment of diabetic macular edema before the development of these morphologic changes may be beneficial for the patient regarding the maintenance of retinal function over a longer time. So, further studies are needed to detect morphological and functional changes after resolution of diabetic macular edema by different modalities of treatment, which could be of prognostic value in cases of DME. |