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Tina T Wong, Arun Naryanaswamy, Henrietta Ho, Hla Myint Htoon, Monisha nongpuir, Li-Fong Seet; Differential iridial gene expression as a novel tool for glaucoma diagnosis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3686.
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© ARVO (1962-2015); The Authors (2016-present)
To determine gene expression profile in glaucoma iris and quantitatively differentiate primary angle closure from primary open angle glaucoma.
Iris tissues were obtained during trabeculectomy surgery by iridectomy from glaucoma patients diagnosed with PACG or POAG. 26 cadaver non-glaucoma iris provided baseline values for comparison. Gene expression in iris was measured by real-time polymerase chain reaction. Anterior segment optical coherence tomography (ASOCT) imaging was also performed for a subset of patients. Gene expression of type I collagen, aquaporin, VEGFA, VEGFB, VEGFC and VEGF receptors 1 and 2 in PACG and POAG iris was compared to non-glaucomatous iris. The biometric parameters anterior chamber depth (ACD), anterior chamber width (ACW), anterior chamber volume (ACV), lens vault (LV), iris area, iris volume and pupil diameter were also measured in PACG and POAG.
Increased expression of aquaporin1, aquaporin 2, VEGFA, VEGFB, VEGFC and VEGFR1 was found in glaucoma iris compared to normal iris. The expression of four genes COL1A1, VEGFB, VEGFR1, VEGFR2 was significantly greater in PACG compared to POAG (P<0.01). The biometric parameters ACD and ACV were significantly smaller (P<0.0005 and <0.01 respectively) and LV significantly larger (P<0.0005) in PACG compared to POAG. The expression of the four genes only, three biometric parameters only and a combination of the gene expression and LV were used in discriminant analyses to distinguish between PACG and POAG, correctly classifying 73.4%, 86.8% and 91.2% of the original cases respectively.
Gene expression profile in glaucoma iris is distinct from non glaucomatous iris, with further distinction found between glaucoma subtypes. A discriminant function based on iris gene expression (COL1A1, VEGFB, VEGFR1, VEGFR2) together with one biometric parameter (LV) is superior to either gene expression data alone or biometric parameters alone for the differentiation of PACG from POAG. Distinct iris gene expression profile is a potentially new tool for the diagnosis of glaucoma, that can discriminate PACG from POAG in addition to known anatomical markers.
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