Tear mixing under a oft contact len: effect of len diameter Original Reearch Article

PURPOE: Tear exchange under a oft contact len i modet, and higher exchange rate may be neceary to reduce extended-wear complication; what i not known i the optimal oft len deign to increae tear mixing. We explored the effect of len diameter on tear mixing. METHOD: Twenty-three ubject wore four different oft contact lene with diameter of 12.0, 12.5, 13.0, and 13.5 mm. Tear mixing wa quantified by placing fluorecein iothiocyanate–dextran on the poterior len urface, inerting the len, and monitoring the change in fluorecence intenity in the potlen tear film. Tear mixing, expreed a the percentage decreae in fluorecence intenity per blink, wa etimated uing an exponential model. Len movement wa videotaped and len comfort wa graded on a 50-point cale (50 = excellent comfort). ubject reporting a comfort level of le than 35 were excluded. REULT: The mean ± E tear mixing rate were 1.82% ± 0.17%, 1.61% ± 0.16%, 1.34% ± 0.17%, and 1.24% ± 0.17% per blink for the 12.0-, 12.5-, 13.0-, and 13.5-mm diameter lene, repectively. By regreion analyi we found that, on average, mixing under the 12.0-mm len wa 0.59% per blink greater than with the 13.5-mm len (P = .0024). Len diameter wa a ignificant predictor of len comfort, and adjuting for the effect of comfort weakened the relationhip between diameter and tear replenihment rate, although the mean rate under the 12.0-mm len wa till 0.43% per blink greater than with the 13.5-mm len (P = .0468). CONCLUION: Thee data ugget that maller-diameter oft lene provide ubtantially better tear mixing than larger lene; however, even mall lene provide modet tear mixing compared with rigid contact lene.