Haddad Mera, Morgan Philip B, Kelly Jeremiah M F, Maldonado-Codina Carole
Optom Eurolens Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK.
Optom Vis Sci. 2011 Oct;88(10):E1188-95. doi: 10.1097/OPX.0b013e318227e30d.
To develop novel methodology to assess two in vivo wettability parameters, contact angle and index of liquid spreading (ILS), for hydrogel contact lenses and to provide a comprehensive investigation of the measurement errors (repeatability) associated with these two parameters.
A Novel On-eye Wettability Analyzer (NOWA) was constructed which delivered a drop of 0.4% sodium hyaluronate mixed with sodium fluorescein directly on to a lens surface in vivo while a two-camera digital system recorded both the resultant contact angle and liquid spreading. Ten subjects each wore a different etafilcon A lens (-0.50 DS) in the right eye for 30 min before measurement on three separate occasions. For contact angles, the coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intrasubject COR, and intersubject COR) was determined. For ILS, the COR associated with two measurement conditions (intrasubject COR and intersubject COR) was also determined.
The in vivo contact angle for the etafilcon A lens was 19.8° ± 2.9° (mean ± standard deviation). COR values for contact angle were 3.2°, 5.2°, and 8.0° for image analysis, intrasubject measures, and intersubject measures, respectively. The mean ± standard deviation ILS was 2.0 ± 0.3 mm, and COR values were 0.4 and 0.8 mm for intrasubject and intersubject measures, respectively.
This research demonstrates that it is possible to obtain hydrogel lens contact angles in vivo and to provide a new wettability parameter (ILS) with the NOWA instrumentation. The COR values obtained were considered to be acceptable. Intersubject COR values were greater than intrasubject COR values for both contact angle and ILS; this is likely to be due to greater variability of tear film characteristics between subjects than within an individual. The use of this novel methodology and its associated clinical parameters across a wider range of lens types in various clinical situations warrants further investigation.
开发新方法以评估水凝胶隐形眼镜的两个体内润湿性参数，即接触角和液体铺展指数（ILS），并全面研究与这两个参数相关的测量误差（重复性）。
构建了一种新型眼上润湿性分析仪（NOWA），它在体内将一滴混合有荧光素钠的0.4%透明质酸钠直接滴到镜片表面，同时一个双摄像头数字系统记录由此产生的接触角和液体铺展情况。10名受试者每人右眼佩戴一片不同的依他氟康A镜片（-0.50 DS），佩戴30分钟后在三个不同时间进行测量。对于接触角，确定了与三种测量条件（图像分析重复性系数、受试者内重复性系数和受试者间重复性系数）相关的重复性系数（COR）。对于ILS，也确定了与两种测量条件（受试者内COR和受试者间COR）相关的COR。
依他氟康A镜片的体内接触角为19.8°±2.9°（平均值±标准差）。接触角的图像分析、受试者内测量和受试者间测量的COR值分别为3.2°、5.2°和8.0°。平均±标准差的ILS为2.0±0.3毫米，受试者内和受试者间测量的COR值分别为0.4毫米和0.8毫米。
本研究表明，使用NOWA仪器可以在体内获得水凝胶镜片的接触角，并提供一个新的润湿性参数（ILS）。所获得的COR值被认为是可接受的。接触角和ILS的受试者间COR值均大于受试者内COR值；这可能是由于受试者之间泪膜特征的变异性大于个体内部。在各种临床情况下，将这种新方法及其相关临床参数应用于更广泛的镜片类型值得进一步研究。
