Study of vitreous liquifaction by NMR spectroscopy and imaging

The vitreous gel is primarily composed of collagen, hyaluronic acid, and water (98-99%) and can break down into a liquid state devoid of collagen. The liquifaction of vitreous gel that occurs with age and in certain other disease states is believed to be important in the pathogenesis of retinal tears and detachments. The authors report measurements of water proton relaxation times and water proton nuclear magnetic resonance (NMR) imaging to study the process of vitreous liquifaction in extracted vitreous and in the intact bovine eye. A comparison is made between macroscopic viscosity, longitudinal (T1) and transverse (T2) relaxation times obtained on an NMR spectrometer and proton NMR images. Vitreous liquifaction as measured by a decrease in macroscopic viscosity resulted after treatment of vitreous with collagenase and to lesser degree with hyaluronidase. A shortening of relaxation times accompanied the drop in viscosity. An area of brightness or increased proton signal intensity corresponding to a focus of liquifaction was seen by NMR imaging only after injection with collagenase. The authors believe NMR imaging to be a useful new diagnostic modality by which vitreous liquifaction can be studied in the intact eye. The vitreous provides a new model for studying changes in proton relaxation times of protein solutions in biologic systems.