Effect of Soft Contact Lens Materials on Tear Film Stability and Central Corneal Radius of Curvature: A Comparative Study of Polymacon and Lotrafilcon B

Abstract

This study investigated the effects of soft contact lens material on the  corneal radius of curvature and the tear film stability. A total of thirty  (n=30) subjects aged between 17 and 33 years with mean age 22.3 ± 3.4 years, made up of 11 males and 19 females were recruited for this study. The corneal radius of curvature (CRC) and non-invasive tear break-up time (NIBUT) were assessed with the Bausch and Lomb Keratometer H-135A (Bausch and Lomb Corp., USA). The subjects were categorised into two groups: Polymacon (conventional soft contact lens) group (n = 17) and lotrafilcon B (O2 optix contact lens) group (n = 13). The difference in NIBUT between pre-task and 2, 4, 6 and 8 weeks of polymacon contact lens wear was statistically significant (ANOVA: P = 0.003). However, for lotrafilcon B, the difference in mean NIBUT was not statistically significant (P = 0.22). The difference in mean CRC between pre-task and 2, 4, 6 and 8 weeks of polymacon and lotrafilcon B contact lens wear was not statistically significant (ANOVA: P > 0.05). The degree of association between CRC and NIBUT was also not statistically significant (p>0.05). This indicates that the tear film stability measured as non-invasive tear break-up time varied under conventional soft (polymacon) lens wear while it remained stable under silicone hydrogel (lotrafilcon B) lens wear. The corneal curvature was not significantly affected by the contact lens materials during the period under study. In conclusion, Lotrafilcon B was a preferred contact lens material since it demonstrated no significant effect on tear film stability as measured as NIBUT.