Quantitative Ultrasonography of Vitreous – imaging the invisible

Abstract

Purpose : Vitreous plays several important roles, including maintaining optical clarity within the eye. However, vitreous opacities develop in myopia and with aging that cause floaters and also degrade contrast sensitivity (CS), a condition called Vision Degrading Myodesopsia [Sebag J: Progr Ret Eye Res 2020 Nov;79:100847]. Managing this and other vitreous diseases is hindered by the lack of good ways to image vitreous. Quantitative ultrasonography (QUS) was developed to image and quantify vitreous density as an index of opacification.

Methods : QUS (Mamou et al: IOVS 56:1611–17, 2015) was performed with clinical instruments (AVISO & ABSolu, Quantel Medical, France) to calculate 4 parameters: Energy (E) ≡ sum of the square of the acoustic values within the region of interest (ROI) divided by the ROI area; Mean (M) ≡ acoustic values divided by the ROI size; P50 ≡ percentage of the ROI filled by clusters of echogenic regions >50 pixels or 0.069 mm; QUS Composite (QUS_c) = (½ E) + (10 x M) + (100 x P50). Findings were correlated with contrast sensitivity (CS) measured with the Freiburg Acuity Contrast Test (increasing Weber Threshold = worse CS), and patient reported outcomes (PROs) using the NEI VFQ-25.

There were 35 asymptomatic controls and 752 VDM cases of different etiologies (328 posterior vitreous detachment (PVD), 168 myopic vitreopathy (MV), 256 MV+PVD) that were evaluated with QUS. Imaging results were correlated with PROs and CS.

Results : Compared to asymptomatic controls, VDM patients had 63% greater vitreous echodensity (553 ± 132 vs. 904 ± 391 AU, p<0.001). There was a strong correlation between QUS_c and CS (R = 0.5497, p<0.00001) as well as between QUS_c and VFQ-25 (R = -0.40, p<0.00001). Patients with MV+PVD had worse QUS, CS, and VFQ-25 than other subgroups. The most informative QUS parameter was composite QUS_c, with R > 0.55 in all subgroup analyses. QUS_c was 81% greater in 321 patients who chose vitrectomy than 430 electing observation. Post-op, QUS_c decreased by 66% (p<0.001).

Conclusions : Increasing vitreous echodensity is associated with worse contrast sensitivity and patient dissatisfaction with vision. QUS enables enhanced vitreous imaging that correlates with CS degradation and patient discontent, making it useful for patient evaluation and management. QUS also provides an objective, quantitative outcome measure for new and existing therapies. QUS thus enables imaging of a structure that no longer remains invisible.

This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.