Niimi Joycelyn, Tan Bo, Chang Jenny, Zhou Yixiu, Ghanekar Avanti, Wong Michelle, Lee Annie, Lin Meng C
Clinical Research Center, School of Optometry, University of California, Berkeley, CA.
Cornea. 2013 Oct;32(10):1305-10. doi: 10.1097/ICO.0b013e31829b21d1.
To identify the diurnal variations of tear osmolarity (TO) and its relationship with central corneal thickness (CCT) and corneal deswelling over a 14-hour period.
TO and CCT were measured using the TearLab Osmometer and Bioptigen spectral domain optical coherence tomography, respectively, on 38 healthy neophytes (mean age, 21.5 ± 2.2 years). TO and CCT were measured at bedtime (baseline), upon awakening, 20 minutes, 40 minutes, 1 hour, 2 hours, 4 hours, and 8 hours after awakening. Deswelling rate was estimated and expressed as percent recovery per hour (PRPH). Mixed-effect linear regression models describe the relationships among TO, CCT, and PRPH.
The tear film upon wakening (264 ± 14 mOsm/L) was hypoosmotic compared with baseline (297 ± 15 mOsm/L, P < 0.001). TO (in mOsm/L) at 20 minutes, 40 minutes, 1 hour, 2 hours, 4 hours, and 8 hours were 287 ± 10, 292 ± 16, 293 ± 12, 292 ± 10, 289 ± 10, and 286 ± 10, respectively. CCT (mean ± SD) at baseline was 552.2 ± 35.9 µm and increased to 572.0 ± 38.7 µm after sleep. CCT returned to baseline thickness 4 hours after awakening (P < 0.000) and remained stable throughout the day. A small but statistically significant association was found between higher TO and lower CCT (P < 0.0001) and between lower baseline TO and higher PRPH (faster deswelling; P < 0.0001).
The diurnal pattern of TO has been established. The association of TO with corneal thickness and deswelling suggests that the tear film tonicity may be partly responsible for corneal hydration control; however, the effect may not be of clinical significance in a normal study cohort.
确定泪液渗透压（TO）的昼夜变化及其在14小时内与中央角膜厚度（CCT）和角膜消肿的关系。
分别使用TearLab渗透压计和Bioptigen光谱域光学相干断层扫描技术，对38名健康新手（平均年龄21.5±2.2岁）测量TO和CCT。在就寝时（基线）、醒来时、醒来后20分钟、40分钟、1小时、2小时、4小时和8小时测量TO和CCT。估计消肿率并表示为每小时恢复百分比（PRPH）。混合效应线性回归模型描述TO、CCT和PRPH之间的关系。
醒来时的泪膜（264±14 mOsm/L）与基线相比为低渗（297±15 mOsm/L，P<0.001）。20分钟、40分钟、1小时、2小时、4小时和8小时时的TO（以mOsm/L为单位）分别为287±10、292±16、293±12、292±10、289±10和286±10。基线时的CCT（平均值±标准差）为552.2±35.9 µm，睡眠后增加至572.0±38.7 µm。醒来后4小时CCT恢复到基线厚度（P<0.000），并在一整天内保持稳定。在较高的TO与较低的CCT之间（P<0.0001）以及较低的基线TO与较高的PRPH（消肿更快；P<0.0001）之间发现了微小但具有统计学意义的关联。
已确定TO的昼夜模式。TO与角膜厚度和消肿的关联表明，泪膜张力可能部分负责角膜水合控制；然而，在正常研究队列中，这种影响可能没有临床意义。
