Charlton J F, Schwab I R, Stuchell R
Department of Ophthalmology, West Virginia University, Morgantown, 26505-9193, USA.
Cornea. 1996 Jul;15(4):335-9. doi: 10.1097/00003226-199607000-00001.
Renal dialysis patients have hyperosmolar bodily fluids due to high urea levels, and accordingly their tears should be hyperosmolar. Tear hyperosmolarity is a sensitive and specific test for dry eye. The purpose of this study was to determine whether renal dialysis patients have hyperosmolar tears and dry eye. Ten renal dialysis patients completed the McMonnies and Ho dry eye questionnaire and underwent tear osmolarity testing before dialysis. Serum osmolarity was calculated from serum sodium, potassium, and blood urea nitrogen levels. Half of the subjects also participated in tear osmolarity testing after dialysis and underwent an eye examination that included rose bengal and fluorescein staining, Schirmer's testing, and tear break-up time testing. All of the subjects had both hyperosmolar serum and tears, and tear osmolarities were positive for dry eye in all subjects. However, none of the subjects tested positively for dry eye with the questionnaire. The subjects had some physical findings consistent with dry eye, and Schirmer's testing showed decreased tear production. Renal dialysis patients are a population that have hyperosmolar tears yet remain asymptomatic for dry eye. Urea has been used for years as a dermatologic treatment for dry skin. The high levels of urea in the tears of dialysis patients may protect them from developing dry eye. Tear hyperosmolarity due specifically to ionized solutes such as sodium and potassium is probably more pathogenic in causing dry eye than is hyperosmolarity in general. Nevertheless, tear osmolarity testing should not be used as a dry eye monitor in renal failure patients.
由于尿素水平高，肾透析患者的体液呈高渗状态，因此他们的眼泪也应是高渗的。泪液高渗是干眼症的一项敏感且特异的检测指标。本研究的目的是确定肾透析患者是否存在高渗性眼泪和干眼症。10名肾透析患者在透析前完成了McMonnies和Ho干眼症问卷，并接受了泪液渗透压检测。根据血清钠、钾和血尿素氮水平计算血清渗透压。一半的受试者在透析后也参与了泪液渗透压检测，并接受了包括孟加拉玫瑰红和荧光素染色、Schirmer试验以及泪膜破裂时间检测在内的眼部检查。所有受试者的血清和眼泪均呈高渗状态，且所有受试者的泪液渗透压检测结果均显示为干眼症阳性。然而，没有一名受试者在问卷检测中显示为干眼症阳性。受试者有一些与干眼症相符的体格检查结果，Schirmer试验显示泪液分泌减少。肾透析患者是一类眼泪呈高渗状态但干眼症无症状的人群。尿素多年来一直被用作干性皮肤的皮肤科治疗药物。透析患者泪液中高水平的尿素可能使他们免于患干眼症。与一般的高渗状态相比，由钠和钾等离子溶质导致的特异性泪液高渗状态可能在引发干眼症方面更具致病性。尽管如此，泪液渗透压检测不应作为肾衰竭患者干眼症的监测指标。
