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Focused Ultrasound Treatment of Vitreous Hemorrhage in an In Vivo Rabbit Model
Gary L Yau1,2,3, Bohao Ning1, Christopher Hu1
1Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
Purpose:
To investigate whether cavitation-based focused ultrasound (FUS) can safely accelerate vitreous hemorrhage (VH) clearance in an in vivo model of VH.
Design:
Preclinical randomized controlled trial.
Subjects:
New Zealand rabbits.
Methods:
Ten rabbits with unilateral experimental VH were randomized to receive FUS (n = 5) or sham treatment (n = 5). The fellow nontreated eye of each rabbit acted as intereye controls (n = 10). Each eye was serially examined until VH resolved, or up to a maximum of 3 months. At each follow-up, clinical examination with indirect ophthalmoscopy was performed which included clinical VH grading, fundus imaging, B-scan ultrasonography, and electroretinography (ERG). After the terminal follow-up, rabbits were sacrificed and enucleated eyes underwent histologic assessment.
Main Outcome Measures:
Primary outcome was time-to-VH clearance based on clinical grading. Secondary outcomes included corresponding B-scan pixel intensity and ERG measurements. Any effects of FUS on nontarget tissues were further described with clinical examination and histologic assessments on enucleated eyes.
Results:
Five out of 5 eyes in the FUS-treated group had an immediate modification of the VH appearance on B-scan, with an average pixel intensity decrease of the VH area by 41 ± 10%. Kaplan-Meier analysis of VH clearance by clinical examination showed that 50% of the FUS-treated eyes reached complete VH clearance by week 3, and all cleared by week 6. Sham-treated eyes started to recover at week 10, and by week 12, probability of recovery was 75%. The difference of treatment effects between these 2 groups was significant (log rank test, P = 0.004). The averaged dark-adapted implicit time between FUS-treated, sham-treated, and control eye groups correlated with the results of the clinical grading of VH. The FUS-treated group did not exhibit any consistent evidence of retinal or optic nerve damage on clinical, ERG, and histology assessment.
Conclusions:
This study demonstrates that cavitation-based FUS therapy accelerates VH clearance in a preclinical model when compared with natural reabsorption ("watchful waiting"). With further refinement of treatment protocol to enhance safety, these findings provide initial support for vitreosonication as a potential noninvasive treatment modality for VH.
Financial Disclosures:
Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
