COMPARISON OF TEAR VOLUME AND OSMOLALITY AMONG WEARERS OF DIFFERENT CONTACT LENS MATERIALS.

Anthony Tran

Abstract

PURPOSE. Contact lens (CL) wearers can have dry eye complaints more often than people who do not wear CL. The purpose of this study was to compare a group of non-CL (NCL) wearers to contact lens wearers with regards to tear film characteristics. METHOD. Forty-seven asymptomatic subjects (mean age 27.0 years) were divided into 4 age-matched groups based on contact lens wear: NCL, Hydrogel CL (HCL), Silicone Hydrogel CL (SHCL) and Rigid Gas Permeable CL (RGPCL). The phenol red thread (PRT) was placed on the lateral lower conjunctival cul-de-sac for 15 seconds and the amount of wetting was measured. Additionally, tear meniscus height (TMH) was measured as a physical estimate of tear volume with a reticle mounted in a biomicroscope. Basal tears were collected and osmolality was measured using a vapor pressure osmometer.

RESULTS. PRT was significantly higher in the NCL group (20.2 mm+4.7) compared to the HCL group (16.4+6.7; p=0.01; t-test), but not statistically different from the SHCL group (17.8+6.4; p=0.16) or the RGPCL group (17.21+8.91; p=0.25). TMH was significantly higher in the NCL group (0.28 mm+0.1) compared to the HCL group (0.21+0.09; p=0.017) and the SHCL group (0.20+0.04; p=0.001), but not for the RGPCL group (0.24+0.07; p=0.19). The mean tear osmolality was lower in the NCL group (307.0 mOsm/Kg+20.0) compared to the HCL group (316.5+27.7; p=0.14), SHCL group (319.0+33.0; p=0.16) but not statistically different. The RGPCL group (323.7+25.9; p=0.027) was significantly different.

CONCLUSIONS. PRT detected a smaller tear pool in the HCL-wearer, which is due to the higher water content of these lenses. The reduced tear meniscus in HCL and SHCL is likely due to tear absorption by the lens, which does not occur in current RGPs. A statistically significant elevation of osmolality was observed only with the RGPCL group, and this efffect may be due to increased evaporation. Determination of tear volume using both PRT and TMH may provide valuable cues to assess dry eye symptoms in CL-wearers.

Details

Year: 2001

Program Number: Poster 124

Author Affiliation: Texas Eye Research and Technology Center

Co-Authors: Amber Gaume, Srihari Narayanan, Norman Leach, William Miller, Jan Bergmanson

Co-Author Affiliation: Texas Eye Research and Technology Center, Texas Eye Research and Technology Center, Texas Eye Research and Technology Center, Texas Eye Research and Technology Center, Texas Eye Research and Technology Center

Room: Exhibit Hall C