A method to probe the mechanical properties of eye tissue has been developed by researchers in the US and Ireland. This could aid both diagnosis of diseased tissue and studies of the effects of age on tissue properties. 

The very delicate nature of eye tissue makes it difficult to directly study the effects of eye diseases. One of the most common methods involves a doctor feeling the eye for regions of different stiffness to normal, but the success is highly dependent on the investigator's skill and the information gained is qualitative. 

Now Alfred Crosby at the University of Massachusetts in Amherst and Jennifer McManus at the National University of Ireland in Maynooth, have shown that a technique used to study synthetic gels, known as cavitation rheology, can be applied to eye tissue. 

Cavitation rheology is performed by connecting a needle to a syringe and inserting it into soft tissue, in this case the vitreous - a gel-like tissue in the eye. The pressure inside the system is gradually increased until, at a particular pressure, a bubble forms at the end of the needle inside the tissue. The pressure at which the bubble appears is related to the mechanical properties of the material. 

'Initially we developed cavitation rheology to measure the mechanical properties of synthetic gels, but the potential to apply the technique to a biological system was always clear,' comments Crosby. 

McManus sees the system's strength lying in its specificity, saying 'this technique allows us to determine the mechanical properties of a specific part, in this case the vitreous, without disturbing any of the other structures inside the eye.' She also points out that cavitation rheology could also be used in other biological tissues. 

Spyros Yannopoulos, an expert in method development for the study of eye diseases at the Foundation for Research and Technology in Patras, Greece, also sees potential in the system, saying that if the method could be used 'to determine the mechanical properties in animals with healthy lenses and animals whose vitreous humors were affected by some eye disease' it would be very useful in showing the pathology of these eye diseases. 

Jon Watson 

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