Tear flow estimates under soft lenses are very low compared to rigid lenses (95% turn-over is achieved in 29 minutes with soft lenses compared to only 6 minutes for rigid lenses). This figure gives a comparison of tear flow under various soft overnight-wear contact lenses. Yoshino M, Yamada M, Kawai M, Mochizuki H, Mashima Y. Measurement of tear replenishment rate under a hard contact lens. Invest Ophthalmol Vis Sci 1996;37 (ARVO Abstracts):S75. Polse K, McNamara N, Brand R. Bulk tear flow under a soft contact lens. Invest Ophthalmol Vis Sci 1997;38 (ARVO Abstracts):S201.