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Jonathan Chou, Clara C Cousins, John B Miller, Lucy Q Shen, Brian J Song, Mae O Gordon, Michael A Kass, Louis R Pasquale; A Novel Quantitative Approach for Analyzing Glaucomatous Disc Hemorrhages: Identifying the Source of the Blood. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3982.
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Optic disc hemorrhages (DH) are often seen in primary open-angle glaucoma (POAG) patients and are associated with glaucoma progression. It is unknown whether optic disc damage causes the hemorrhage, or whether the hemorrhage is an upstream event, making the optic disc more susceptible to damage. Understanding whether DH come primarily from arterial or venous sources may shed some light on this subject. An arterial source suggests that DH are primary events secondary to vascular dysregulation, while a venous source suggests that DH are secondary events due to distortions of the lamina cribrosa. We developed a technique to assess the densitometry and geometric profiles of DH.
Two observers used ImageJ to compare DH (n=25 eyes) to known sources of retinal venous and arterial blood; branch retinal vein occlusion (BRVO; n=28 eyes), and retinal macroaneurysms (MA; n=19 eyes), respectively, using stock internet images. Subsequently, analysis was performed using DH images from the Ocular Hypertension Treatment Study (OHTS; n= 10) and Mass Eye & Ear (MEE; n= 19) POAG patients. Mean grayscale pixel intensity (densitometry), circularity value (4π x area/perimeter sq), and length/width ratio were calculated. Pixel intensity of the hemorrhage was compared to adjacent retinal arterioles and venules (fig 1). The densitometry of the arteriole and venule minus the densitometry of the hemorrhage (ΔA and ΔV, respectively) were measured (fig 2).
DH were more likely to have densitometry readings similar to adjacent arterioles and brighter than adjacent venules (ΔA = 10.68 ± 6.22, ΔV = -4.11 ± 7.99) compared to BRVO hemorrhages (ΔA = 24.65 ± 18.67, p = 0.0008; ΔV = 6.62 ± 16.64, p = 0.005) in stock internet images. MA hemorrhages had a densitometry between the other two groups (ΔA = 16.05 ± 11.15, ΔV = 0.87 ± 9.79). DH also tended to have an elongated shape (length/width = 3.73 ± 1.48; circularity = 0.49 ± 0.12). Similar trends were seen in DH photos from OHTS/MEE (ΔA = 7.49 + 7.02; ΔV = -3.16 + 7.20; length/width ratio = 5.18 + 2.32; circularity = 0.40 + 0.13). There was good inter-reader reliability for all assessments (intraclass correlation coefficient ≥ 0.78).
DH appear to be primarily arterial in origin. Their geometric shape suggests that they are expelled from vessels under high shear stress. These results suggest that DH may result from vascular dysregulation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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