Agreement between invasive and noninvasive measurement of tear film breakup time

Abstract The agreement between fluorescein breakup time (FBUT) estimates and noninvasive breakup time (NIBUT) estimates automatically acquired using two videokeratoscopes was assessed. Small-cone (E300, Medmont) and large-bowl (K5M, OCULUS) Placido-ring–based videokeratoscopes were utilized for automated NIBUT estimation and fluorescein strip method was used for FBUT estimation. 33 subjects completed the study. Clear instructions were given regarding the blink before measurements. Bland–Altman analysis was used to test the agreement between tear film breakup time estimates and repeated measure analysis of variance was used to test the differences between measurement types. In comparison to FBUT, E300 NIBUT estimate was shorter (− 0.6 ± 2.6 s), whereas K5M NIBUT estimate was longer (3.3 ± 2.4 s). Limits of agreement for FBUT vs. E300 was 29.8 s, for FBUT vs. K5M 26.4 s, and 31.4 s for E300 vs. K5M. There were significant differences between tear film breakup times (F = 3.59, df = 2, P = 0.032). E300 and K5M NIBUT measurements have poor agreement with FBUT, even when blinking is precisely clarified. Agreement was better for shorted break up times than that for longer ones but in general NIBUT measurements are not interchangeable

Noninvasive In Vivo Assessment of Soft Contact Lens Type on Tear Film Surface Quality

PURPOSE. To evaluate the effect of soft contact lens type on the in vivo tear film surface quality (TFSQ) on daily disposable lenses and to establish whether two recently developed techniques for noninvasive measurement of TFSQ can distinguish between different contact lens types. METHODS. Thirteen subjects wearing four different types of daily soft contact lenses participated in the study. Dynamic area high-speed videokeratoscopy (HSV) and lateral shearing interferometry (LSI) were used to quantitatively assess TFSQ in natural blinking conditions in the morning soon after lens insertion and in the afternoon following 8 hours of lens wear. RESULTS. All considered contact lenses caused a significant reduction in TFSQ compared with bare eye measures. Significant differences (P Ͻ 0.05) in the average TFSQ were also observed between all contact lens materials in LSI measurements and in the majority of dynamic area HSV measurements. The potential relationship between the contact lens parameters and the observed decline in the prelens TFSQ was explored. CONCLUSIONS. Noninvasive techniques of tear film surface assessment have the potential to discriminate contact lens type/ material on eye. LSI was found to more effectively perform this discrimination than the dynamic area HSV technique. (Invest Ophthalmol Vis Sci. 2012;53:525-531) DOI:10.1167/iovs.11-8257 I t is well known that the presence of a contact lens in the eye disrupts the precorneal tear film by dividing it into prelens and postlens tear film layers. 6 -8 Contact lens-induced tear film changes are significant clinically because a large proportion of contact lens wearers report dry eye symptoms, 9 and symptoms of dryness have been found to be a primary reason for contact lens intolerance. 16 -21 For example, Thai et al. In contrast to these studies of the in vivo effects of contact lenses on the tear film, in vitro studies examining contact lens surface properties that are likely to be related to contact lenstear film interactions, such as contact lens surface wettability 22-25 and lens surface roughness, 26,27 have typically noted (sometimes substantial) significant differences among different lens types in terms of these characteristics. The reason in vivo studies have not found differences associated with different contact lens types, despite evidence of significant differences in the surface wetting characteristics of different lenses, is unclear. It is possible that individual patient-related tear film factors in these studies had a greater effect on in vivo tear film measures than differences in contact lens surface wettability between lens types. 28 In this study we used two recently developed noninvasive techniques 29 -33 that have been shown to exhibit high precision 32 for tear film measures and to discriminate dry from normal eyes 33 to quantitatively investigate the quality of the prelens tear film with different contact lens types. We aimed to evaluate the effect of a range of different daily disposable soft contact lens types on tear film surface quality and to establish whether the noninvasive measurement techniques used can distinguish between the different contact lens types. From th

Application of texture analysis in tear film surface assessment based on videokeratoscopy

Purpose\ud Videokeratoscopy images can be used for the non-invasive assessment of the tear film. In this work the applicability of an image processing technique, textural-analysis, for the assessment of the tear film in Placido disc images has been investigated.\ud \ud Methods\ud In the presence of tear film thinning/break-up, the reflected pattern from the videokeratoscope is disturbed in the region of tear film disruption. Thus, the Placido pattern carries information about the stability of the underlying tear film. By characterizing the pattern regularity, the tear film quality can be inferred. In this paper, a textural features approach is used to process the Placido images. This method provides a set of texture features from which an estimate of the tear film quality can be obtained. The method is tested for the detection of dry eye in a retrospective dataset from 34 subjects (22-normal and 12-dry eye), with measurements taken under suppressed blinking conditions.\ud \ud Results\ud To assess the capability of each texture-feature to discriminate dry eye from normal subjects, the receiver operating curve (ROC) was calculated and the area under the curve (AUC), specificity and sensitivity extracted. For the different features examined, the AUC value ranged from 0.77 to 0.82, while the sensitivity typically showed values above 0.9 and the specificity showed values around 0.6. Overall, the estimated ROCs indicate that the proposed technique provides good discrimination performance.\ud \ud Conclusions\ud Texture analysis of videokeratoscopy images is applicable to study tear film anomalies in dry eye subjects. The proposed technique appears to have demonstrated its clinical relevance and utility