Craig J P, Singh I, Tomlinson A, Morgan P B, Efron N
Department of Vision Sciences, Glasgow Caledonian University, UK.
Eye (Lond). 2000 Aug;14 ( Pt 4):635-41. doi: 10.1038/eye.2000.156.
To determine whether the more rapid cooling of the tear film in dry eyes is related to other tear film parameters, a battery of tear physiology tests was performed on dry eye patients and control subjects.
Tear evaporation rate was measured with a modified Servomed (vapour pressure) evaporimeter and ocular temperature with an NEC San-ei 6T62 Thermo Tracer in 9 patients diagnosed as having dry eye and in 13 healthy control subjects. Variability in temperature across the ocular surface was described by the temperature variation factor (TVF). Lipid layer structure and tear film stability were assessed with the Keeler Tearscope and tear osmolality was measured by freezing point depression nanolitre osmometry.
The data were explored by principal component analysis. The subjects with and without dry eye could be separated into two distinct groups entirely on the basis of their tear physiology. Dry eye patients exhibited higher tear evaporation rates, osmolalities and TVF, lower tear film stabilities and poorer-quality lipid layers than the control subjects. A significant linear relationship was found to exist between tear evaporation rate and TVF for all subjects (R2 = 0.242, p = 0.024).
Rapid cooling of the tear film in dry eyes appears to be related to the reduced stability of the tears and the increased rate of evaporation. The higher latent heat of vaporisation, associated with the increased evaporation in dry eyes, may account for the increased rate of cooling of the tear film in this condition.
为了确定干眼患者泪膜更快冷却是否与其他泪膜参数相关，对干眼患者和对照受试者进行了一系列泪液生理学测试。
使用改良的Servomed（蒸气压）蒸发仪测量泪液蒸发率，并用NEC San-ei 6T62热成像仪测量9名诊断为干眼的患者和13名健康对照受试者的眼表温度。通过温度变化因子（TVF）描述眼表温度的变化。使用Keeler泪液镜评估脂质层结构和泪膜稳定性，并用冰点降低纳升渗透压法测量泪液渗透压。
通过主成分分析对数据进行探索。干眼患者和非干眼患者可以完全根据其泪液生理学分为两个不同的组。干眼患者的泪液蒸发率、渗透压和TVF较高，泪膜稳定性较低，脂质层质量较差。所有受试者的泪液蒸发率与TVF之间存在显著的线性关系（R2 = 0.242，p = 0.024）。
干眼患者泪膜的快速冷却似乎与泪液稳定性降低和蒸发率增加有关。与干眼蒸发增加相关的较高汽化潜热可能是导致这种情况下泪膜冷却速率增加的原因。
