1. Field of the Invention
The present invention is related to detecting a flow of tissue and fluid aspirated from an eye. More specifically, the present invention is related to detecting a difference in viscosity between different materials being aspirated.
2. Description of the Related Art
During Ophthalmic Surgery both anterior and posterior surgery various materials, some transparent, are removed from an eye by aspiration, while other transparent materials are simultaneously infused into the eye. In anterior surgery the materials removed include a cataractous or clear lens, vitreous, cortical material and the infused material includes balanced-salt-solution (BSS) and viscoelastic. BSS and viscoelastic are infused to ensure that the eye stays inflated as an eye collapse during surgery can lead to catastrophic results. Posterior surgery material removed includes vitreous humor (vitreous), which is a clear gel filling the space between the lens and retina.
It is often difficult to distinguish between the various materials being removed because there is little visual difference between the different materials, except in the case of cataracts, which are easily identified. Also, a surgeon's ability to visualize the materials can be compromised by the eye's anatomy and inadequate illumination and magnification. The inability to distinguish between the materials being removed can lead to wasted time removing fluids infused into the eye, rather than removing the targeted natural tissue. This is especially true in posterior surgery during vitrectomy, where significant time can be spent removing BSS to ensure that all the vitreous is removed prior to operating on the diseased or torn part of the retina.
One difference between BSS and vitreous is the viscosity, where BSS is water and vitreous is a much more viscous gel.
Therefore, it would be desirable if there were a feedback mechanism or alert that could inform a surgeon when the instrument removing material from the eye encounters a different material, particularly when a change in viscosity of the removed material is encountered.