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ABSTRACT
PURPOSE: The coefficient of friction was empirically derived for a series of commercially available ophthalmic lubricants having potential use during laser in situ keratomileusis (LASIK).
METHODS: Measurements were obtained using a modified tensile testing machine. Solutions tested included the artificial tear supplements Polytears-free, Bion Tears, Genteal, Refresh, Cellufresh, Celluvisc, Theratears, and Viscotears gel; and balanced salt solution (BSS).
RESULTS: Viscotears carbomer gel had a significantly lower mean coefficient of friction compared to other ophthalmic lubricants tested (P=.002) and the dry plate (P=.005). Addition of 0.1 ml of BSS to 0.025 ml of Celluvisc significantly reduced the coefficent of friction of Celluvisc (P=.01). Polytears, Bion Tears, Genteal, Refresh, Celluvisc, Theratears, and BSS had coefficients of friction significantly higher than that of the dry plate.
CONCLUSION: A range of values were obtained for the coefficient of the ophthalmic lubricants tested. Viscotears gel (0.1 ml), and Celluvisc (0.025 ml) + BSS (0.1 ml) had coefficients of friction significantly lower than that of the dry plate. [J Refract Surg 2001;17:327-333]
The coefficient of friction is a physical property of a liquid material related to its ability to provide lubrication under opposing shearing forces as two surfaces are moved relative to each other. One of the main roles of an ophthalmic lubricant is to protect the ocular surface by supplementing the tear film and reducing resistance between the ocular surface and the lids in conditions of poor tear film stability.1?2 The authors think that this property of ophthalmic lubricants should be measured, as it also has potential applications in the selection of a lubricant to be used during laser in situ keratomileusis (LASLK).
The ability to minimize surgical trauma to the ocular surface created by the passage of the microkeratome over the corneal epithelium during LASLK is of paramount importance to the surgical outcome. Ocular surface management during surgery influences the comfort, ocular surface recovery, refractive and visual outcome, and corneal clarity after surgery, as reported by Lenton and colleagues (Lenton LM, Albietz JM. Effect of carmellose base artificial tears on the ocular surface in eyes after laser in situ keratomileusis. J Refract Surg 1999;15(suppl):S227-S231) and others.3?4 Corneal epithelial trauma during surgery can result in epithelial defects, micro-epithelial erosions and epithelial ingrowth; epithelial dehiscence, stromal swelling, and...