Age-related changes in vitreous mobility as measured by video B scan ultrasound

Many vitreoretinal disorders increase in incidence with age. The vitreous is known to liquefy and separate from the retina in aging patients. Liquefaction and partial vitreous separation alter the biomechanics of the vitreous and change the tractional forces exerted by the vitreous on the retina. These forces may play a role in the development of a variety of vitreoretinal pathologies including retinal tears, cystoid macular edema, and macular holes. The purpose of this study is to test the hypothesis that the biomechanical properties of the vitreous change with aging and can be quantified by analysis of kinetic B scan ultrasound recordings. Kinetic B scan ultrasound recordings were made of the vitreous gel of 38 subjects from ages 18 to 91 during standard eye motions. The recordings were graded for speckle density (hyperreflective areas on ultrasound) and were examined for the presence or absence of posterior vitreous detachment. Tracking of the speckles on a polar grid allowed for the calculation of the angle travelled by the speckle relative to the angle travelled by the eye. The recordings were also analysed for "overshoot time", or the amount of time that the speckles continued to travel after the cessation of eye movement. The vitreous of subjects of age less than 46 years demonstrated significantly less speckle density (P < 0.001), less overshoot time (P < 0.001), and less angle travelled by the speckle relative to the angle travelled by the eye when compared to older subjects (P = 0.006). The presence or absence of PVD as diagnosed by kinetic ultrasound was not a significant predictor for speckle density, overshoot time, or ratio of angular motions. The results indicate that aging affects the biomechanics of the vitreous in ways which can be quantified with kinetic ultrasound analysis using the grading system described above.