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B. O. Lundgren, R. Bergman, M. Lundqvist, S. Mannberg, R. Shimizu, R. Steinert; Correlation Between Physico-Chemical Parameters and Performance of Ophthalmic Viscosurgical Devices (OVD) During Cataract Surgery in Animal Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1069.
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Phacoemulsification with use of an OVD is the preferred technique of modern cataract surgery. The OVD maintain the anterior chamber, protects the corneal endothelium and facilitates IOL implantation. The clinical impression is that dispersive OVDs retain in the anterior chamber and protect the endothelium better during phacoemulsification than cohesive OVDs. The purpose with this study was to correlate physico-chemical parameters of different OVDs with their performance (anterior chamber maintenance and retention) at different stages of the surgical procedure.
The physico-chemical parameter cross over frequency of the OVDs (when elastic and viscous properties are equal) was determined using a rheometer using oscillatory test methods.For the ex vivo experiment fresh eyes from newly slaughtered pigs were used. Anterior chamber depth (ACD) was measured using a NIDEK-1000 scheimpflug camera. Images were obtained before surgery, after injection of OVD, after capsulorhexis and finally after crystalline lens removal using phacoemulsification. For each product investigated at least eight eyes were used. Products tested were Healon, Healon GV, Healon5, Provisc, Viscoat, Discovisc and Amvisc Plus.
Cross over frequency was higher for low molecular mass dispersive products and lower for high molecular mass cohesive products. The cohesive products showed a better anterior maintenance capacity for filling and capsulorhexis while the dispersive products showed a better retention capacity during phacoemulsification. One product, the viscoadaptive cohesive Healon5, showed the best anterior maintenance capacity for the early stages of the surgical procedure and also retained in the eye to the same extent as the dispersive products.
Selection of OVDs for existing and novel surgical procedures should balance the use of rheological data and ex vivo analyses. Using these approaches, surgeons can optimize their selection of OVDs to meet the demands of surgical procedures.
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