Mathers W D, Daley T E
Department of Ophthalmology, University of Iowa Hospials and Clinics, Iowa City, 52242-1091, USA.
Ophthalmology. 1996 Apr;103(4):664-9. doi: 10.1016/s0161-6420(96)30637-4.
To evaluate the steady-state tear flow and evaporation from the ocular surface of patients with and without dry eye.
Two groups of patients, 21 with dry eye and 34 without dry eye, with similar age distributions were selected by criteria based on tear osmolarity, Schirmer test, meibomian gland loss, and dry eye symptoms and were compared for tear flow, tear volume, percent turnover, and surface evaporation.
Tear flow averaged 0.10 +/- 0.08 microliters/minute in patients with dry eye versus 0.15 +/- 0.12 microliters/minute in patients without dry eye (P = 0.002). Tear volume averaged 2.13+/- 1.3 microliters in patients with dry eye versus 2.23 +/- 2.5 microliters in patients without dry eye (P = not significant) and tear turnover averaged 5.3 +/- 2.9% in patients with dry eye versus 8.2 +/- 4.3% in patients without dry eye (P = 0.019). Evaporation averaged 25 +/- 35 X 10(-7) g/cm(2)/second in patients with dry eye versus 13 +/- 6 X 10(-7) g/cm(2)/second in patients without dry eye (P = 0.003).
Measured tear flow was significantly lower than previously determined in patients with and without dry eye. Evaporation was increased in patients with dry eye and accounted for the majority of the tear loss in patients with dry eye. Normal tear osmolarity can be maintained, even with low tear flow, if evaporation is kept within the normal range.
评估有无干眼患者眼表的稳态泪液流量及蒸发情况。
根据泪液渗透压、泪液分泌试验、睑板腺缺失及干眼症状等标准，选取两组年龄分布相似的患者，其中21例为干眼患者，34例为非干眼患者，比较两组的泪液流量、泪液体积、更新率及表面蒸发情况。
干眼患者的泪液流量平均为0.10±0.08微升/分钟，而非干眼患者为0.15±0.12微升/分钟（P = 0.002）。干眼患者的泪液体积平均为2.13±1.3微升，非干眼患者为2.23±2.5微升（P值无统计学意义），干眼患者的泪液更新率平均为5.3±2.9%，非干眼患者为8.2±4.3%（P = 0.019）。干眼患者的蒸发平均为25±35×10⁻⁷克/平方厘米/秒，非干眼患者为13±6×10⁻⁷克/平方厘米/秒（P = 0.003）。
测量得到的泪液流量显著低于既往对有无干眼患者的测定值。干眼患者的蒸发增加，且蒸发是干眼患者泪液损失的主要原因。如果蒸发保持在正常范围内，即使泪液流量较低，也可维持正常的泪液渗透压。
