Miller William L, Doughty Michael J, Narayanan Srihari, Leach Norman E, Tran Anthony, Gaume Amber L, Bergmanson Jan P G
Texas Eye Research and Technology Center, University of Houston, College of Optometry, Houston, TX 77202, USA.
Eye Contact Lens. 2004 Jul;30(3):132-7. doi: 10.1097/01.icl.0000138714.96401.2b.
Various measures are available to assess the tear film, yet little specific information is available on how they relate to each other. An exploratory study was undertaken to assess three measures and their relationship in non-contact lens wearers and in contact lens wearers.
Forty-three young subjects (mean age, 25.0 +/- 3.1 years; 19 men and 24 women) without overt ocular disease were recruited and categorized into four similarly sized groups based on contact lens wear (no lens wear, conventional daily wear hydrogels, silicone hydrogel lenses worn on a continuous basis, and gas-permeable contact lenses). Sets of measures, in random order and from both eyes whenever possible, were made using a phenol red thread (PRT) test over 15 seconds (open eye), biomicroscopy to assess tear meniscus height (TMH) from a perpendicular perspective using a 0.05-mm resolution graticule, and a borosilicate glass micropipette used to collect a 5-microL sample of tears for assessment of osmolality by vapor pressure measures.
For the complete group of subjects, the TMH data averaged 0.22 +/- 0.07 mm; the average PRT wetting length was 18.0 +/- 6.1 mm; and the tear osmolality averaged 317 +/- 28 mOsm/kg. The intereye differences averaged 0.04 mm for TMH, 3.7 mm for PRT, and 15 mOsm/kg for tear osmolality. There were no detectable sex-related differences in the measures. Compared with the control group (average, 0.25 mm), the TMH data showed a trend to be lower in daily hydrogel (0.21 mm) and silicone hydrogel (0.20 mm) lens wearers, but not in gas-permeable lens wearers (0.24 mm). PRT data was bimodally distributed, with the control group showing slightly higher (average, 21.1 mm) wetting compared with hydrogel lens wearers (16.7 and 17.4 mm) and gas-permeable lens wearers (average, 17.3 mm). Hydrogel (319 mOsm/kg for both groups) and gas-permeable lens wearers (average, 324 mOsm/kg) had higher tear osmolality measures compared with the control group (average, 305 mOsm/kg). Although some of the differences approached statistical significance, any statistical differences were evident only after outliers were removed. However, on pooling all data, there was a statistically significant positive correlation between TMH and open-eye PRT measures (P < 0.001) and an indication of a negative correlation between open-eye PRT and tear osmolality measures.
Even contemporary contact lens wear can have a small but measurable impact on the precorneal tear film osmolality or volume. The changes are internally consistent and, overall, support the idea that the PRT test provides a useful measure of tear meniscus volume.
有多种方法可用于评估泪膜，但关于这些方法之间如何相互关联的具体信息却很少。本研究旨在对非隐形眼镜佩戴者和隐形眼镜佩戴者的三种评估方法及其相互关系进行探索性研究。
招募了43名无明显眼部疾病的年轻受试者（平均年龄25.0±3.1岁；19名男性和24名女性），并根据隐形眼镜佩戴情况分为四个规模相近的组（未佩戴隐形眼镜、传统日戴水凝胶镜片、连续佩戴硅水凝胶镜片、透气硬镜）。尽可能从双眼以随机顺序进行一系列测量，包括使用酚红棉线（PRT）测试15秒（睁眼），通过生物显微镜从垂直角度使用0.05毫米分辨率的标尺评估泪河高度（TMH），以及使用硼硅酸盐玻璃微量移液器收集5微升泪液样本，通过蒸气压测量法评估泪液渗透压。
在全部受试者中，TMH数据平均为0.22±0.07毫米；PRT平均湿润长度为18.0±6.1毫米；泪液渗透压平均为317±28毫摩尔/千克。双眼间差异平均为TMH 0.04毫米、PRT 3.7毫米、泪液渗透压15毫摩尔/千克。这些测量指标未发现明显的性别差异。与对照组（平均0.25毫米）相比，日戴水凝胶镜片（0.21毫米）和硅水凝胶镜片（0.20毫米）佩戴者的TMH数据有降低趋势，但透气硬镜佩戴者（0.24毫米）无此趋势。PRT数据呈双峰分布，对照组的湿润度略高于水凝胶镜片佩戴者（16.7和17.4毫米）和透气硬镜佩戴者（平均17.3毫米）（平均21.1毫米）。水凝胶镜片佩戴者（两组均为319毫摩尔/千克）和透气硬镜佩戴者（平均324毫摩尔/千克）的泪液渗透压测量值高于对照组（平均305毫摩尔/千克）。尽管部分差异接近统计学显著性，但只有在去除异常值后，统计学差异才明显。然而，汇总所有数据后，TMH与睁眼PRT测量值之间存在统计学显著正相关（P<0.001），睁眼PRT与泪液渗透压测量值之间有负相关趋势。
即使是现代隐形眼镜佩戴也会对角膜前泪膜渗透压或泪液量产生微小但可测量的影响。这些变化具有内在一致性，总体上支持PRT测试可有效测量泪河泪液量这一观点。
