TEAR FLOW AND SOFT CONTACT LENSES

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Abstract
Tear flow was determined in 14 persons before and after 1 mo. of adaptation to a soft contact lens (Soflens, Bausch and Lomb), with a radioactive tracer (99mTc as pertechnetate), .gamma.-camera and computer system. The elimination of the radioisotope from the conjuctival sac was diphasic with a significant increase of the fractional turnover rate after the adaptation period in the initial phase with a rapid elimination; no change occurred in the basal phase with a slower elimination. The fractional turnover rate was determined with the soft contact lens placed on the cornea after having been pre-soaked in the Tc solution resulting in a value of 0.021 .+-. 0.003 min-1 (mean .+-. SEM [standard error of mean], n = 12). The fractional turnover rate resulting from instillation of the radioisotope on the non-pre-soaked soft contact lens placed in the eye was 0.020 .+-. 0.004 min-1 (mean .+-. SEM, n = 6). In studies with the soft contact lens in the eye, the elimination curves were monophasic and not diphasic as in normal tear flow studies.