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Brittany Routledge, Jeannie Nguyen-Cuu, Kenneth M.P. Yee, J Sebag; Posterior Vitreous Displacement in the Supine Position. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2015.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior vitreous detachment (PVD) features anterior movement of the posterior vitreous away from the retina and optic disc. This study evaluated whether the distance from the posterior pole to the posterior vitreous cortex is different when patients sit erect versus lie supine.
17 eyes in 12 subjects (5 males, 7 females; age = 72 ± 12 years) with PVD were evaluated using ultrasonography (USG). All patients had no significant past ocular history except for 5 eyes (4 subjects) with a history of cryopexy/laser prophylaxis for anomalous PVD and retinal breaks. USG was performed using a probe optimized for vitreous imaging (Mamou et al IOVS 56:1611–7, 2015; 15-MHz center frequency, 20-mm focal length, 7-mm aperture) with vertical scans taken in primary gaze and through premacular vitreous in temporal gaze. USG was performed with each subject sitting erect, then lying supine. Each scan set had 100 frames, of which 3 frames in each orientation with identifiable optic disc and posterior vitreous cortex were used to perform 3 measurements of the distance from the posterior vitreous cortex to the optic disc in each frame, constituting 9 measurements per subject, which were averaged.
Repeatability (standard deviation of the mean) of the measurement procedure was excellent: 0.079 in the erect position and 0.058 in the supine position. In 15/17 subjects there was a shorter distance between the posterior vitreous cortex and the optic disc when subjects were supine (2.35 ± 0.71 mm) as compared to sitting erect (2.99 ± 0.98 mm); (p < 0.019).
The posterior vitreous cortex is 27.2% closer to the optic disc when subjects are supine as compared to sitting erect. This may partly explain why patients often report that floaters are more noticeable when lying on their backs. Future studies should determine if there are similar or different findings in older age, myopic vitreopathy, and pseudophakia, all conditions known to affect vitreous biochemical composition, rheology, and structure.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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