الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Glaucoma is a major cause of irreversible visual morbidity worldwide. Primary Open-angle glaucoma is the most common form of glaucoma associated with an open anterior chamber angle by gonioscopy. POAG is generally bilateral, but often asymmetric. Glaucoma characterized by chronic, slowly progressive optic neuropathy caused by degeneration of RGC and their axons with progressive enlargement of C/D ratio and a consequent thinning of the neuroretinal rim with irreversible but preventable visual field loss. It is generally asymptomatic until late in the disease when the central vision is affected. Therefore early detection and appropriate treatment is essential. Glaucoma diagnosis requires frequent longitudinal monitoring and detection of progressive damage over time. OCT and OCTA are objective, noninvasive, easy imaging devices providing reproducible and high resolution images of ocular structures relevant to glaucoma, comparing the observed measurements with normative databases and differentiating optic nerve damage from normal variation.
The aim of this study was to evaluate optic disc by optical coherence tomography and optical coherence tomography angiography in primary open angle glaucoma. This was a prospective cross sectional study, including 57 eyes of 40 subjects. Subjects were divided into 2 groups which were: group A (20 patients with POAG) and group B (20 normal subjects). Each subject was investigated by Zeiss Cirrus 6000 HD OCT , Zeiss Angioplex OCT Angiography, Fundus photography by Heidelberg Engineering Gmbh 2017, and visual field testing, by Humphrey visual field analyser (HFA). Any patient with other retinal vascular disease that may affect the results like DM, venous occlusions, etc., or with media opacity that affects the quality of OCT and OCTA scans like corneal opacities, cataract, etc., or with congenital optic disc anomalies, or having previous surgical interventions like history of retinal surgery, previous intravitreal injections or recent anterior segment surgery was excluded.
Statistically, this study observed high significant differences between the two studied groups according to IOP, ONH OCT parameters (except disc area), RNFL thickness, ONH perfusion detected by OCTA and visual field parameters. In POAG, ONH OCT parameter (rim area) and RNFL thickness were significantly thinner with larger C/D ratio and with reduced ONH perfusion detected by OCTA compared to normal controls.
In POAG, regarding RNFL quadrant, the inferior quadrant was the most affected RNFL quadrant followed by the superior quadrant. In normal group, the inferior quadrant is the thickest followed by the superior quadrant, then nasal quadrant and finally the temporal quadrant.
Correlations of duration of POAG and IOP with RNFL thickness and ONH parameters detected by OCT and ONH perfusion detected by OCTA were statistically examined and showed significant correlations except with (cup volume and superior RNFL quadrant). The strongest correlation occurred between the duration of POAG and average RNFL.
In POAG, functional glaucomatous damage detected by visual field testing was significantly correlated with structural glaucomatous damage detected by (ONH, RNFL) OCT and the highest correlation of visual field parameters occurred with average RNFL thickness and rim area.
In POAG, reduced ONH perfusion detected by OCTA was significantly correlated with structural glaucomatous damage detected by (ONH, RNFL) OCT and the strongest correlation occurred with rim , average RNFL and inferior RNFL quadrant thickness. In normal, OCTA flux index showed a weak statistically significant correlation with inferior RNFL quadrant thickness. There was a statistically significant correlation between reduced ONH perfusion detected by OCTA and functional glaucomatous damage detected by visual field testing.
In POAG, correlation of ONH OCT parameters with RNFL thickness showed statistically significant correlations. Almost all ONH OCT parameters correlated especially with average RNFL and the inferior RNFL quadrant and the strongest correlation occurred between rim area and the average RNFL thickness followed by the superior RNFL quadrant.
In normal group, correlation of ONH OCT parameters with RNFL thickness was statistically examined and showed that rim area had a statistically significant correlation with average and quadrants RNFL thickness except nasal quadrant. The strongest correlation was between rim area and average RNFL thickness followed by the inferior RNFL quadrant.
In conclusion, in POAG patients, duration of POAG and IOP level have an effect on RNFL thickness and ONH parameters detected by OCT and ONH perfusion detected by OCTA. OCT detects that ONH parameters and RNFL thickness are severely affected in POAG and significantly different from normal controls. There is relationship between the functional loss (as measured with Standard automated perimetry SAP) and structural loss (as detected with RNFL thickness and neuroretinal rim area measurements by OCT). In POAG, using of OCTA showed reduced ONH perfusion or vascular DROP out when compared to healthy controls. The ONH perfusion, as measured by OCTA, has vascular- structural and vascular-functional correlations especially in the RPC. Measurement of OCTA and quantitative analysis of disc perfusion could present a useful, non-invasive, and objective approach to the diagnosis of glaucoma.