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Kenneth M Yee, Jonathan Mamou, Ronald H Silverman, Justin Nguyen, Jeffrey A Ketterling, J Sebag; Quantitative Ultrasonography of Vitreous Correlates with Contrast Sensitivity and Visual Acuity. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4366. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Vitreous floaters can significantly impact quality of life when affecting contrast sensitivity (CS) and visual acuity (VA) but there are no objective measures of vitreous structure for clinical evaluation of floaters. This study developed quantitative analysis of B-scan ultrasound (QUS) to measure vitreous echodensities as an index of disease severity and to determine if QUS correlates with functional deficits in CS and VA.
QUS reproducibility was tested in 10 eyes of 10 subjects. 35 eyes from 28 patients (56 + 18 yrs; 17 men, 11 females) with subjective vitreous floaters were assessed by QUS using a customized probe (15 MHz center frequency, 20 mm focal length, 7 mm aperture) in three different scan orientations (longitudinal, LONG; transverse, TRANS; and longitudinal to the macula, LMAC) yielding three parameters (energy, E; mean amplitude, M; and percentage of the vitreous body filled by echodensities, P50) from whole-central vitreous. Statistical analyses evaluated E, M, and P50 correlations with CS (%W, Freiburg Acuity Contrast Test) and VA (decimal of Snellen ratio).
QUS was highly reproducible in the LMAC (rICC > 0.90) and LONG (rICC > 0.83) orientations. In 35 eyes with floaters, CS ranged from 1.2 %W (normal) to 5.6 %W (worst) (mean = 2.7 + 1.2 %W) and decimal VA ranged from 1.0 to 0.33 (mean VA = 0.76 + 0.19). Three QUS measures at each of two different scan orientations correlated significantly with VA: E in the LMAC scan orientation (R = -0.57, P<0.0004), E in the TRANS scan (R = -0.56, P<0.0006), M in the LMAC scan (R = -0.60, P<0.0002; Fig 1) M in the TRANS scan (R = -0.60, P<0.0002), p50 in the LMAC scan (R = -0.44, P<0.008) and p50 in the TRANS scan orientation (R = -0.48, P<0.004).<br /> <br /> These same six QUS measures strongly correlated with CS: E in the LMAC scan orientation (R=0.77, P<5.0 x 10-8), E in the TRANS scan (R=0.73, P<6.7 x 10-7), M in the LMAC scan (R=0.76, P<10-8), M in the TRANS scan (R=0.78, P<3.0 x 10-8; Fig 2), p50 in the LMAC scan (R=0.68, P<7.3 x 10- 6) and p50 in the TRANS scan orientation (R=0.71, P<1.8 x 10-6).
QUS objectively provides quantitative assessment of vitreous structure across a wide range of vitreous echodensities. QUS indices correlate with VA and CS suggesting that QUS could provide a clinically useful index of vitreous structural abnormalities in floaters and other conditions.
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