الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 51 |  |  |
| | | from | 51 | | |
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.