The rheological behaviour of animal vitreus and its comparison with vitreal substitutes

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Some important eye pathologies, such as diabetic proliferative retinopathy and retinal detachment, are strictly connected to different gel vitreus alterations. Therefore there is a strong need in ophthalmology for vitreal substitutes. Until now many synthetic and natural polymers have been tested as vitreal substitutes, but no one has proved to be an ideal vitreal substitute. An ideal vitreal substitute, apart from other characteristics, such as transparency, permanency, biocompatibility, etc. must have a rheological behaviour compatible with the surrounding tissues. The viscoelastic behaviour of different animals' gel vitreus, evaluated by means of steady shear viscosity and small-amplitude oscillatory measurements, is typical of solid-like rubbery gels with dynamic elastic modulus G′ higher than the dynamic viscous modulus G″ in the typical frequency range investigated (0.05–10 Hz). On the other hand the rheological behaviour of current or candidate vitreal substitutes (silicone oil, HPMC, high molecular weight hyaluronic acid and chemically-crosslinked hyaluronic acid), analysed with the same technique, is generally different from that of natural vitreus.

Department of Materials and Production Engineering, University of Naples “Federico II”