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lin an, Peng Li, Murray Johnstone, Ruikang Wang; Optic Nerve Head Label-free Microangiography: OCT-based Correlation of Microstructure and Microvasculature in Normal & Open Angle Glaucoma Subjects. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4458.
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To determine the feasibility of correlating optic nerve head (ONH) structure with functioning microvasculature in the ONH and scleral rim using a 3D OCT imaging technique.
OMAG, a label-free OCT vascular imaging procedure, operating at 842 nm central wavelength was modified to image ONH microstructure and microcirculations. Human subjects (7) [Normal Eyes (10), OAG (4); Mean age (35)] participated in this pilot study. OMAG acquired 3D volumetric datasets from each subject, providing simultaneous structural and microvascular images of the ONH.
The tissue organization and functional blood flow as acquired by OMAG appear similar among the normal subjects. The typical images acquired from one normal subject are shown in Fig 1: Rows (80, 180, 400 and 600µm depth); Columns (a-j=structure, b-k=microvasculature; c-i=merged). (a-c) NFL capillaries branching from retinal artery. (d-f) ONH vessels enter from level of choroid to supply prelaminar layer. (g-i) lamina cribrosa (LC) is continuous with sclera. Vessels penetrate sclera to supply LC capillaries; vascular pattern mirrors LC beam architecture. (j-l), deeper LC and vascular pattern persist, less regular organizational pattern than in (g-i). Large vessels are visible at external edge of scleral rim in region of circle of Zinn-Haller. Fig. 2: Typical images acquired from one glaucoma subject’s ONH: (a -b) cross-sectional structure & corresponding vascular images (temporal-nasal section), indicating thinning of prelaminar layer. (c-d) enface views of the LC, 100µm below the ONH surface; LC-porous structure (c) is visible; unlike Fig. 1g pore architecture is compressed & non-uniform. In Fig. 2d, unlike Fig.1h, capillaries mirroring LC beam architecture are absent, presumably dropping out & leaving large CRA vessels visible in this deep cup.
OMAG can provide detailed images of functioning capillaries as well as larger vessels that supply ONH tissue beds. Correlation between simultaneous structural and blood flow images provided in vivo evidence of mutual relationships. OAG eyes had a striking loss of vasculature, particularly in the lamina cribrosa. The non-invasive label-free technology should prove beneficial clinically in identifying and monitoring vascular components of mechanisms associated with ONH damage in glaucoma.
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