Abnormal morphology of and flow in the microvasculature is a hallmark of SCA. However, objective measurements of these abnormalities has been limited. Using computer-assisted intravital microscopy, 5 adult patients with SCA were studied and compared with normal controls (n=50). Videotaped images of the bulbar conjunctival vessels were acquired using an intravital microscope mounted on a modified slit-lamp table. No ophthalmic medications were used. Coded video sequences were selected and analyzed using the program VASCAN developed in our laboratory. Subjective review of the sequences revealed characteristic obstructed comma- or curlicue-shaped small vessels and markedly reduced flow. Arterioles were poorly organized and disjointed. Venules were larger than normal: patients 83 μm (52-89 μm) [mean (range)] vs. controls 54 μm (50-6μm) Marginally perfused areas (defined as areas ≥ 120 um from an arteriole) were also greater in the SCA patients: 23% (8-33%) (SCA) vs. 7% (5-10%) (controls). Severe morphologic and flow abnormalities are present in the conjunctival vasculature of patients with SCA and can be quantitated with intravital microscopy. Longitudinal studies are ongoing to further define these abnormalities, and to measure in vivo blood flow changes in the bulbar conjunctiva in relation to clinical events.
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