Tear film dynamics from ocular surface imaging in dry eye and contact lens wear

Abstract

The difficulty associated with the current techniques drove the investigations presented in the present thesis which aimed at investigating the clinical usefulness of corneal topography and slit lamp videography in the assessment of tear film dynamics in dry eye and contact lens wear.Six-hundred and forty-two (642) eyes of 321 subjects took part in Study 1 where several parameters were derived from corneal topography and slit lamp videography, and the assessment of meibomian gland dysfunction (MGD) and Schirmer test with anaesthesia (STA) made. Tear film break-up time (TFBUT) was significantly correlated with STA (tear production test), MGD (tear production and tear elimination tests), and lipid floating time (LFT) (p < 0.05). Corneal irregularity measurement (CIM) after 5 seconds of holding the blink (CIM 5) had significant correlation with LFT while CIM after 8 seconds of blink holding (CIM 8) was significantly correlated with MGD. Furthermore TFBUT, LFT, and tear meniscus height (TMH) were significantly reduced in the dry eye group compared to non-dry eye group. In Study 2 parameters from slit lamp videography (as derived in Study 1), plus pre-lens tear film (PLTF) non-invasive tear break-up time (obtained from corneal topography) were followed-up in the investigation of the effects of 8 hours of contact lens wear comparing that of each subject’s own habitual hydrogel contact lens to newly-prescribed daily silicone hydrogel contact lens. Thirty six (36) eyes of 18 habitually wearing hydrogel contact lenses (mean age =22.9 ± 3.7 years old) were involved, and it was found that PLTF, TFBUT, and LFT were all significantly reduced (p < 0.05) after wearing each lens type for 8 hours. The tear film changes noted for each lens type after the 8 hours of wear were however, not significantly different (p > 0.05) between habitual hydrogel and the silicone hydrogel contact lenses. In Study 3 the tear ferning patterns (indirect tear production test) were compared among non-contact lens wearing, soft contact lens wearing, and post-contact lens related microbial keratitis (Post-CLRMK) subjects. Abnormalities in the tear ferning pattern of the habitual contact lens wearing subjects and post-CLRMK subjects were statistically similar (p > 0.05). In conclusion corneal topography and slit lamp videography have been shown from the studies presented in this thesis to be useful clinical tests representing the phases of tear production, distribution and elimination, for the assessment of tear film dynamics in the clinical setting.