Ren H, Petroll W M, Jester J V, Cavanagh H D, Mathers W D, Bonanno J A, Kennedy R H
Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas 75235-9057, USA.
CLAO J. 1997 Jan;23(1):63-8.
Previous studies have shown that contact lens oxygen transmissibility correlates with binding of Pseudomonas aeruginosa to the rabbit cornea after overnight lens wear. Studies of human lens wear stratified by oxygen transmissibility will be required to validate these animal results. In humans, bacterial binding to shed cells obtained through corneal irrigation cytology may provide an indirect measure of in vitro binding. The purpose of this study was to establish the relationship between binding to shed cells and to the residual corneal surface in an animal model of lens wear prior to initiation of human studies.
The test contact lenses used were: rigid lens A (Dk/L = 10 x 10(-9) [cm/ sec][mL O2/mL mmHg]); rigid lens B (Dk/L = 97); soft lens A (Dk/L = 9); soft lens B (Dk/L = 20); and, soft lens C (Dk/L = 39). There were six rabbits in each group, except for the soft lens C group, which had seven rabbits. After overnight lens wear, the corneal surface was irrigated with a corneal irrigation chamber to collect surface cells before exposure to a bacterial suspension (1 x 10(7) CFU/mL) for 30 minutes. The number of bacteria adherent to the residual corneal surface was then assessed by CFU determination. Cells collected from the corneal surface (9 mL) were incubated with 1 mL bacterial suspension containing 10(8) (CFU/mL) for 30 minutes. The number of bacteria adherent to shed cells was assessed by staining with acridine orange and direct counting by epifluorescence microscopy.
The differences in the number of bacteria adhering to shed epithelial cells between the treated and the control eyes were 2.90 +/- 1.20 and 0.23 +/- 0.41 for rigid lenses A and B, respectively, and 5.97 +/- 1.54, 3.67 +/- 2.32, and 0.90 +/- 1.45 (bacterial/cell) for soft lenses A, B, and C, respectively. Overnight contact lens wear induced a significant increase in bacterial binding to shed corneal epithelial cells for rigid lens A and for soft lenses A and B. There were significant differences among lens groups (P = 0.00017, ANOVA), with significant differences between rigid lenses A and B, soft lenses A and C, and soft lenses B and C. The binding of bacteria to shed cells was significantly correlated with the binding of bacteria to the residual corneal surface, both confirming and extending previous results (R = 0.78, P < 0.001).
These results demonstrate a positive correlation between P. aeruginosa adherence to shed corneal cells and to the residual corneal surface in the rabbit eye following contact lens wear. In light of the results from prior animal studies, examination of the behavior of P. aeruginosa binding to exfoliated cells appears to be a promising and valid method for future assessment of similar lens-induced increases in bacterial binding in prospective human clinical studies.
先前的研究表明，过夜佩戴隐形眼镜后，隐形眼镜的透氧性与铜绿假单胞菌在兔角膜上的黏附有关。需要进行按透氧性分层的人类隐形眼镜佩戴研究，以验证这些动物实验结果。在人类中，通过角膜冲洗细胞学获得的脱落细胞上的细菌黏附情况，可能提供体外黏附的间接测量方法。本研究的目的是在开展人体研究之前，在隐形眼镜佩戴动物模型中，确定脱落细胞黏附与角膜残留表面黏附之间的关系。
使用的测试隐形眼镜有：硬性镜片A（Dk/L = 10×10⁻⁹ [cm/sec][mL O₂/mL mmHg]）；硬性镜片B（Dk/L = 97）；软性镜片A（Dk/L = 9）；软性镜片B（Dk/L = 20）；以及软性镜片C（Dk/L = 39）。除软性镜片C组有7只兔子外，每组有6只兔子。过夜佩戴隐形眼镜后，用角膜冲洗室冲洗角膜表面以收集表面细胞，然后在暴露于细菌悬液（1×10⁷ CFU/mL）30分钟之前进行收集。然后通过CFU测定评估黏附在角膜残留表面的细菌数量。从角膜表面收集的细胞（9 mL）与1 mL含10⁸（CFU/mL）的细菌悬液孵育30分钟。通过吖啶橙染色和落射荧光显微镜直接计数来评估黏附在脱落细胞上的细菌数量。
对于硬性镜片A和B，处理眼与对照眼中黏附在脱落上皮细胞上的细菌数量差异分别为2.90±1.20和0.23±0.41，对于软性镜片A、B和C，差异分别为5.97±1.54、3.67±2.32和0.90±1.45（细菌/细胞）。过夜佩戴隐形眼镜导致硬性镜片A以及软性镜片A和B黏附在角膜脱落上皮细胞上的细菌显著增加。镜片组之间存在显著差异（P = 0.00017，方差分析），硬性镜片A和B、软性镜片A和C以及软性镜片B和C之间存在显著差异。细菌与脱落细胞的黏附与细菌与角膜残留表面的黏附显著相关，既证实又扩展了先前的结果（R = 0.78，P < 0.001）。
这些结果表明，佩戴隐形眼镜后，兔眼中铜绿假单胞菌在角膜脱落细胞上的黏附与角膜残留表面上的黏附呈正相关。鉴于先前动物研究的结果，检查铜绿假单胞菌与脱落细胞的黏附行为，似乎是未来在前瞻性人体临床研究中评估类似镜片诱导的细菌黏附增加的一种有前景且有效的方法。
