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he foveal avascular zone (FAZ) is the capillary-free area in the central macula. Various methods including histology, immunohistochemistry, fundus fluorescein angiography (FFA), and indocyanine green angiography (ICGA) have been used to evaluate the retinal vasculature.
OCTA is a novel technique that is used to visualize the retinal microvasculature without dye injection. Thus, the FAZ area can be clearly assessed without the concern of any dye leakage.
Current study aimed to evaluate dimensions of foveal a vascular zone at level of superficial and deep capillary plexuses in patients with different grades of non-proliferative diabetic retinopathy without maculopathy using optical coherence tomography angiography and to correlate these changes with the best corrected visual acuity, glycemic control of the patients and retinal neuro degenerative changes.
This study was conducted on 100 eyes of 66 patients, who were randomly selected and agreed to participate in the study in the period from February 2018 to August 2018 divided into 20 eyes of normal healthy individuals and 80 eyes of diabetic patients which will be sub divided into four sub groups:
Study group (a): 20 eyes with diabetic patients without DR.
Study group (b): 20 eyes with mild NPDR.
Study group (c): 20 eyes with moderate NPDR.
Study group (d): 20 eyes with severe NPDR.
Full history was taken from the patient and was subjected to measurement of HbA1c and careful ocular examination including BCVA (Log. MAR), IOP, anterior segment examination, pupillary reflexes and posterior segment examination using indirect ophthalmoscopy and slit lamp biomicroscopy. Then all patients were examined by. OCT for measurement of total thickness, ganglion cell complex layer thickness and outer retinal layer thickness, cup / disc ratio and peripapillary RNFL thickness then OCTA for evaluation of foveal avascular zone.
The results of the present study revealed a statistically significant enlargement of FAZ in patients with moderate NPDR group in SCP and severe NPDR group in both SCP and DCP with more accurate delineation of the edges of these zones using OCTA and there was a statistically significant positive correlation between FAZ in SCP and in DCP and BCVA (Log MAR).
There was no statistically significant difference found between control group and patients’ group regarding full macular thickness as we exclude diabetic macular odema.
There was no statistically significant difference was found between control group and patients’ group regarding peripapillary retinal nerve fiber layer thickness and cup to disc ratio.
There was a statistically significant decrease in mean superior, inferior, nasal, temporal, ganglion cell complex layer thickness in sever NPDR group and in mean superior ganglion cell complex layer thickness in moderate NPDR group versus controls and there was, a statistically significant negative correlation between FAZ in SCP with superior, inferior, nasal, temporal and central ganglion cell complex layer thickness.
There was a statistically significant decrease in mean central and inferior (ORL) thickness in severe NPDR group and in mean central (ORL) thickness in moderate NPDR group and in mean inferior (ORL) thickness in no retinopathy group versus controls and there was a statistically significant negative correlation between FAZ in SCP and central (ORL) thickness.
These vascular and neurological changes were moderately correlated to each other and to BCVA and severity of the diseases. These may determine the prognosis prior to any further treatments.
Further studies are needed to correlate the results of OCTA to FFA findings and design a new protocols based on the present results for treatment and follow up of those patients after treatment