|Title||WHY DO SOME CONTACT LENS WEARERS AVOID CONTACT LENS DRY EYE SYMPTOMS?|
|Author, Co-Author||Alan Tomlinson, Raied Fagehi, Velitchko Manahilov|
Room 225 A-B
|Abstract|| PURPOSE: To assess the differences in tear physiology and in-vivo lens wettability in patients who were symptomatic and asymptomatic in contact lens wear. This was an attempt to define the factors which lead to complaints of contact lens dry eye (CLDE).
METHODS: Seven symptomatic contact lens wearers were identified from 9 asymptomatic patients by the OSDI questionnaire, by a score of > 10. Tear turnover rate TTR (by scanning fluorophotometry) and evaporation rate (by vapor pressure evaporimetry) were measured together with osmolarity (by freezing point depression osmometry ) following lens wear. The wettability of the lens surfaces in -vivo were assessed by thin film interferometry (Doane interferometer) by onset latency (OL-the time until the first dry spot appeared), the drying duration (DD- time after OL until the lens surface became completely dry), maximum speed of drying (MS - the peak velocity of the increase in dry area), and peak latency (PL- time until maximum speed was achieved).
RESULTS: Tear evaporation rate was raised from normal levels in both groups (38.70 +/- 11.42 and 38.78 +/- 8.71 g/m2/h for symptomatic and asymptomatic patients respectively) and osmolarity showed no change (307.42 +/- 6.97 and 303.33 +/- 9.74 mOsmol/L). Tear turnover was normal in symptomatic but significantly higher in asymptomatic subjects (20.78 +/_ 6.86 and 33.83 +/- 8.81 %/min). Measures of lens wetting, namely OL, DD and PL were significantly higher in symptomatic than asymptomatic wearers ( OL- 22.35 +/- 16.78 and 10.63 +/- 2.21 secs; DD - 36.05 +/- 19.74 and 25.23 +/-7.53 secs; PL - 30.08 +/- 25.45 and 14.86 +/- 4.34 secs) but MS was similar.
CONCLUSIONS: The increased tear turnover rate in asymptomatic contact lens wearers could account for the absence of symptoms in this group despite the increased evaporation which should predispose them to an evaporative dry eye state. The better wetting shown by lenses worn by the symptomatic patients did not appear to provide enough benefit to offset the loss of tear fluid through evaporation (in the presence of normal tear turnover).
|Affiliation of Co-Authors||Glasgow Caledonian University, Glasgow Caledonian University|